Certus Standard
Scanning Probe Microscope
with optical video microscope
User manual
Nano Scan Technologies Ltd.
Zavodscaya St 7, Dolgoprudniy, Russian Federation, 141700
Pnone: +7 (495) 665-00-85
+7 (495) 642-40-68
+7 (495) 642-40-67
E-mail: info@nanoscantech. com
web: www. nanoscantech. com
2011
This user guide is intended for installation and operation of a Scanning Probe Microscope Certus Standard. Scanning Probe Microscope Certus Standard is a combination of XYZ scanner, cantilever tip sensor (deflectometer), SPM controller EG-3000,
software Nspec and optical video microscope.
Before installation and operation this appliance, please read the manual. On all
matters related to technical support and upgrades for this product, under the additional
features, contact the following addresses:
Phone: +7 (495) 665-00-85
+7 (495) 642-40-68
+7 (495) 642-40-67
E-mail: info@nanoscantech. com
web: www. nanoscantech. com
Skype: NanoScanTech
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Read this first!
Laser radiation.
When you work in certain modes, using a scanning probe microscope (SPM)
Certus Standard, laser light sources of varying power and wavelength are used. Before
working with SPM Certus Standard, we encourage you to read the documentation for
the specified source of laser radiation and safety for the class of the laser source. In the
case of an external laser in the recording system of the microscope or with a combination of SPM Certus Standard with external laser sources, we recommend that you study
the documentation and safety for your laser source.
Precautions.
SPM Certus Standard – this is a complex research tool. Strong physical impacts, operation in hostile environments, changes in the structure during use, storage or
transportation can result to device damage.
Modification and user self-alignment of SPM Certus Standard with research
equipment.
In the case of user self-alignment of SPM Certus Standard with research equipment, or modification to the specific research tasks recommended to agree the matter
with the company "Nano Scan Technology", because the user self-interference in the
construction without the agreement deprives the warranty.
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Contents
Contents
Introduction.................................................................................................9
1. Basic information...................................................................................10
1.1. Field of applications of the SPM Certus Standard........................................10
1.2. Overview of the SPM Certus Standard..........................................................11
1.3. Specification......................................................................................................12
1.3.1. Data Sheet...................................................................................................12
1.3.2. Sample size..................................................................................................13
1.3.3. Deflectometer lasers....................................................................................13
1.3.4. SPM Certus Standard dimensions...............................................................14
1.4. Operating conditions........................................................................................15
1.5. Safety regulations..............................................................................................16
1.6. Terms of storage and transportation..............................................................17
1.6.1. Storage........................................................................................................17
1.6.2. Transportation.............................................................................................17
1.7. Description of basic units.................................................................................18
1.7.1. Scanning head Certus.................................................................................20
1.7.2. Controller EG-3000....................................................................................24
1.7.3. Certus Standard microscope base...............................................................26
1.7.4. Videomicroscope.........................................................................................27
1.7.5. NSpec Software...........................................................................................28
2. Operating principles..............................................................................29
2.1. SPM common principles..................................................................................29
2.2. Probe scanning/positioning..............................................................................31
2.2.1. Scanning......................................................................................................31
2.2.2. Piezoelectric phenomena............................................................................32
2.2.3. Lever translation systems............................................................................33
2.2.4. Displacement sensors..................................................................................35
2.3. Probes.................................................................................................................36
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2.3.1. Basic probe parameters..............................................................................36
2.3.2. Probe drawings...........................................................................................37
2.4. Cantilever Z position detection system...........................................................38
2.4.1. Deflector registration system......................................................................38
2.4.2. “Shear-force” registration system..............................................................40
2.5. Feedback............................................................................................................42
2.6. Combining optical and scanning probe microscope......................................42
3. Start operation.......................................................................................44
3.1. SPM Certus Standard installation..................................................................44
3.2. Installation of vibration protection.................................................................44
3.3. Installation SPM Certus Standard base and videomicroscope....................45
3.3.1. Installation of the stand...............................................................................46
3.3.2. Installation of the arm.................................................................................46
3.3.3. Installation of the microscope mover..........................................................47
3.3.4. Installation of the videomicroscope............................................................48
3.4. SPM Certus installation...................................................................................49
3.4.1. SPM Certus head description......................................................................49
3.4.2. Probe holder connection.............................................................................52
3.4.3. Installation SPM Certus on the base...........................................................54
3.5. EG-3000 controller connection........................................................................55
3.6. PC connection...................................................................................................56
3.7. Videocamera connection to the computer......................................................56
3.8. Remote controller connection..........................................................................56
3.9. NSpec software installation..............................................................................57
3.10. SPM Certus Standard «on/off» regulation...................................................58
3.10.1. «On» rules.................................................................................................58
3.10.2. «Off» rules.................................................................................................59
3.11. NSpec basic options........................................................................................59
4. Working with SPM Certus Standard...................................................62
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4.1. The list of base operating modes.....................................................................62
4.2.
Basic SPM Certus Standard operations (atomic-force microscope
techniques)..................................................................................................................62
4.3. Adjustment of range and bias of the capacity sensors..................................63
4.4. Adjustment of PID control...............................................................................64
4.5. Probe installation..............................................................................................65
4.6. Sample mounting..............................................................................................67
4.7.
Information about NSpec software required for SPM Certus Standard
adjustment..................................................................................................................69
4.7.1. Plot mode control........................................................................................70
4.7.2. Cantilever resonant frequency acquisition..................................................70
4.7.3. Oscilloscope mode......................................................................................71
4.7.4. Land/lift curves............................................................................................72
4.8. Deflectometer system adjustment...................................................................73
4.8.1. Laser beam alignment to cantilever bulk....................................................73
4.8.2. PSD (position sensor diode) alignment.......................................................75
4.8.3. Search of the reflected beam.......................................................................76
4.8.4. Alignment the reflected beam with the PSD center.....................................77
4.8.5. Probe resonant frequency acquisition.........................................................78
4.9. Feedback parameters.......................................................................................80
4.9.1. Additional scan parameters........................................................................83
4.9.2. General recommendations of feedback parameters....................................83
4.9.3. Setpoint tuning............................................................................................83
4.9.4. Probe Z axes control...................................................................................84
4.10. Sample stage positioning................................................................................84
4.11. Probe approaching to the sample..................................................................85
4.11.1. The control of the stepper motors..............................................................85
4.11.2. Stepper motors settings..............................................................................87
4.11.3. Remote control adjustment........................................................................88
4.11.4. Tip approaching.........................................................................................90
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4.11.5. Head leveling.............................................................................................90
4.11.6. Head tilting and coarse approaching........................................................90
4.11.7. Fine approaching......................................................................................91
4.11.8. Approaching by remote controller.............................................................91
4.12. Sample positioning..........................................................................................92
4.13. Adjustment of scan parameters.....................................................................92
4.13.1. Signal description......................................................................................95
4.13.2. Multi-pass technique.................................................................................97
4.13.3. Additional scan parameters......................................................................97
4.13.4. Selection of scanning parameters.............................................................99
4.13.5. Scanning conditions..................................................................................99
4.14. Scanning........................................................................................................100
4.15. Primary image processing and saving........................................................101
4.16. Precise probe positioning.............................................................................102
4.17. Scanner calibration.......................................................................................103
4.18. Calibration procedure..................................................................................106
4.18.1. Calibration mode....................................................................................106
4.18.2. Piezostack calibration.............................................................................107
4.18.3. Sensors calibration..................................................................................107
4.18.4. Tool panel Settings..................................................................................108
4.18.5. Calibration coefficients obtaining...........................................................109
5. SPM Certus head application with external optical equipment......113
5.1. Basic principles of optical equipment application.......................................113
5.2. Example...........................................................................................................114
5.3. Video-videocam mode adjustment................................................................114
5.4. Video unit basic functions..............................................................................115
5.5. Lenses calibration...........................................................................................118
5.5.1. Settings panel main functions....................................................................118
5.5.2. Tools panel Settings...................................................................................119
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5.5.3. New lens calibration.................................................................................120
5.5.4. Scan field selecting....................................................................................120
5.6. Microscope positioning...................................................................................122
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Introduction
Introduction
This user guide describes SPM Certus Standard, specifically designed for work
with optical equipment, such as optical microscopes, spectrometers and other similar
devices.
Universal SPM controller EG-3000 and software NSpec is required for SPM
Certus operation.
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Basic information
1. Basic information
1.1.
Field of applications of the SPM Certus Standard
Certus Standard – specialized scanning probe microscope (SPM), specially designed to work with optical equipment for combining the techniques of scanning probe
microscopy and optical microscopy and spectroscopy. XYZ scanning head with piezoceramic stacks is a base of the system.
SPM Certus Standard is designed for imaging and studying the surface properties
of various substances, materials and structures, both natural and artificial. For example,
the study of surface properties of polymer, biological, inorganic, and semiconductor materials, biological cells, tissues, individual biological structures and biomolecules,
covered, electronic equipment, etc.
With SPM Certus Standard you can solve the following problems:
• Topography imaging;
• Surface roughness determination;
• Surface force spectroscopy;
• Nano lithography;
• To obtain relevant information about the physical and chemical properties
of the sample surface;
• Obtain optical microscopic images of reflected light;
• Precise SPM probe positioning with optical microscope.
General list of tasks implemented by the SPM Certus, determined by the used
method.
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Basic information
1.2.
Overview of the SPM Certus Standard
Fig. 1.1 Overview of the SPM Certus Standard.
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Basic information
1.3.
Specification
1.3.1. Data Sheet
Main data sheet
1
1.1
SPM scanning head
Built-in XYZ scanner (flat stage)
1.1.1 Range
100x100x15 μm
1.1.2 XY resonant frequency
1 kHz
1.1.3 Z XY resonant frequency
7 kHz
1.1.4 Lateral (XY) resolution
<1 nm
1.1.5 Vertical (Z) resolution
<0.1 nm
1.1.6 Residual non-linearity
<0.3%
1.1.7 Minimum scanning step
0.1 nm
1.2
Displacement sensors
1.2.1 Sensors type
Capacitance
1.2.2 Operation principle
1.3
Scanner material
1.4
Landing system
TDC (time to digital convertors)
Aluminum alloy
1.4.1 Minimum step
1 μm
1.4.2 Implementation of the landing system
1.4.3 Number of stepper motor
1.5
Stepper motor
3
Sample positioning
1.5.1 Coarse sample positioning range
5x5 mm
1.5.2 Implementation of the coarse sample positioning
1.5.3 Positioning error
2
Microscrews
~5 μm
Optical microscope
2.1
Implementation
2.2
Zooming
2.3
The range of fine-tuning
2.4
Video registration
2.5
Lighting
2.6
Video system optical parameters
Digital video microscope
Manual
5 mm
Digital color video camera
Fiber illumination
2.6.1 Numerical aperture
0.3
2.6.2 Camera sensor size
1/3”
2.6.3 Camera sensor resolution, px
1280x1024
2.6.4 Magnification
85x/1050x
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2.6.5 Field of view
4.50/0.37 mm
2.6.6 Interface
USB
1.3.2. Sample size
min
Any
max without SPM
Up to Ø 230 mm and 30 mm height.
max with SPM
Up to Ø 125 mm and 16 mm height.
1.3.3. Deflectometer lasers
Default
650 nm, <1 mW, Class II
IR
1300 nm, <1 mW, Class II
External
User defined
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Basic information
1.3.4. SPM Certus Standard dimensions
Fig. 1.2 SPM Certus Standard dimensions
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Basic information
1.4.
Operating conditions
SPM Certus Standard is a complex, high-precision research instrument. To ensure
normal operation of the device are advised to observe the following conditions of use
and storage:
1
Temperature
1.1
Range
10÷50°С
1.3
Optimum
22±3°С
*When delivered, SPM Certus Standard scanner adjusted to the optimum operating temperature. When the
room temperature is different from the optimum, but within the permissible operating temperature range, neces sary to calibrate the scanner at current temperature in the room.
2
Humidity
2.1
Maximum
80 %
2.2
Optimum
65±15 %
3
Atmospheric pressure, mm. Hg
760±30
4
Power requirements
4.1
Voltage, V
4.2
Frequency, Hz
4.3
Ground
5
110/220 (+10%/-15%)
50/60
required
Noise and vibration
5.1
Vibration sensitivity range, Hz
1÷100
5.2
Maximum vibration magnitude in range
0.5 μm
5.3
Maximum sound pressure within 10000 Hz
35 dB
6
Shield from:
6.1
Direct sun light
required
6.2
Heating
required
6.3
Electromagnetic radiation
required
6.4
Air/gas flow
required
7
Extra recommendation
7.1
Frequent and abrupt changes in temperature and humidity, affect to performance and the quality of the
results.
7.2
Running compressors, traction control, laminar boxes, cooling devices, and similar sources of periodic or
random noise can create background noise.
7.3
Recommended to place Certus Standard with maximum possible distance from the computers, monitors
and peripheral devices.
7.4
Avoid strong mechanical influences on Certus Standard, as this may lead to failure of the mechanics
and control electronics unit.
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Basic information
1.5.
1
Safety regulations
Safety regulation
1.1
Ground
Recommended to check equipment ground
1.2
Opened parts
Work is prohibited, with the removed cover and the casing.
1.3
Cables connect/disconnect
Cables connecting/disconnecting to device connectors can be done
while device is off.
1.4
mount/dismount device units
Only specialists of «Nano Scan Technology», certified specialists, in consultation with «Nano Scan Technology»
1.5
External equipment connec- Only in agreement with the company «Nano Scan Technology»
tion
1.6
Liquid
2
Not accepted.
Laser radiation sources
2.1
Deflectometer laser
In accordance with the class of security established by the laser safety
class and characteristics of the laser described in the SPM head under
the label shown in Fig. 1.2.
2.2
External lasers
In accordance with the marking on external sources of laser radiation
Fig. 1.3 The warning label on the laser source.
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Basic information
1.6.
Terms of storage and transportation
1.6.1. Storage
The device should be stored in compressed form in a special room with no abrupt
changes in temperature and humidity.
1
Temperature
2
Humidity
22±10°С
Maximum 80%
1.6.2. Transportation
When transporting, instrument should be packed in the original package or in any
other package, which excludes the damage. After transport at temperatures below 0°C,
before starting the device, wait 3 hours.
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Basic information
1.7.
Description of basic units
SPM Certus Standard includes the following parts:
• SPM head Certus;
• Optical microscope with illumination and video camera;
• Base with mechanical motions for samples and optical video microscope
positioning;
• EG-3000 Controller;
• NSpec software.
A
Scanning head Certus
B
Optical microscope
C
Digital video camera
D
Base with mechanical motions for samples and optical video microscope positioning
Fig. 1.4 Basic units of the SPM Certus Standard.
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Basic information
A
Scanning head Certus
B
Base with the mechanical movers for samples and an optical video microscope positioning
C
Optical microscope
D
Digital video camera
E
Illumination device
F
Vibration protection (in the base set - granite slab)
Fig. 1.5 Overview of the SPM Certus Standard
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Basic information
1.7.1. Scanning head Certus
The basis of the scanning probe microscope Certus Standard is a scanning head of
the new generation. The main distinguishing features of SPM Certus are:
• Built-in XYZ flat scanner (scanning stage) with capacitive displacement
sensors;
• Modular architecture, allows to use different lasers for deflectometer, including external laser sources;
• easily removable probe holder, which allows to use of fundamentally different types of probes;
• open work area (the contact point of the probe and the sample), which
provides easy monitoring of the probe, the input of external radiation, etc.;
• parallel to the probe to sample approach system with the ability to automatically align the head over the plane of the sample;
• Full digital connection between the head and the controller.
Plane scanner (stage) is a monolithic metallic body (made of high quality Al alloy), in which with EDM and other methods of precision machining, formed channels
for piezoelectric actuators (piezoelectric stacks), moving parts of the scanner, etc. This
design provides excellent linearity and flatness of travel, in contrast to piezoelectric
tubes, a scan surface which is a sphere. In addition, the plane-scanners have high mechanical stability compared to the brittle piezoelectric-tubes.
In the basic mode SPM Certus operate as atomic-force microscope (AFM). As additional modes are implemented: scanning tunneling microscope, scanning Hall probe,
Kelvin mode and other modes of scanning probe microscopy.
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Basic information
A
Certus head body with built in XYZ flat scanner (stage).
B
Probe holder.
C
Screws for laser beam to cantilever bulk alignment.
D
Screws for reflected laser beam to PSD diode alignment.
E
High precision actuators for approach system.
Fig. 1.6 SPM Certus head.
Certus head scanner is equipped with capacitive displacement sensors. The measuring method is based on TDC (time-to-digital converters), that are physically located
as close as possible to the sensors, that give digital signal proportional to measured capacitance. This method enables high-precision measurements and transmission current
sensors position to the controller, with long cables without sacrificing the quality of
measurements.
In the standard configuration deflectometer diode laser with a wavelength of 650
nm is used. At the request of the customer may use another, for example infrared, laser.
In addition, fiber optic port can be installed for connecting an external laser.
The head comes with several detachable probe holders: standard cantilevers, tun«Nano Scan Technologies Ltd.»
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Basic information
ing-fork type probes with a vertical or horizontal orientation. Probe holders for any original probes can be developed by the request of customers.
Unique "open design" of the SPM Certus enables high multiples of the external
lenses, illuminations, condensers microscopes, etc. to illuminate the work area, to view
the sample and the probe, to take stock of the radiation to the point of contact tip and
sample.
For the Certus head control, universal the controller EG-3000 and the software
NSpec are using.
Fig. 1.7 SPM Certus drawings.
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Basic information
Basic technique
1
1.1
1.2
SPM Certus
Atomic-force microscopy (AFM)
1.1.1 Contact AFM
In base configuration
1.1.2 Resonance semicontact (AFM tapping mode)
In base configuration
1.1.3 Resonance noncontact
In base configuration
1.1.4 Phase imaging
In base configuration
1.1.5 Adhesion force imaging
In base configuration
1.1.6 Force spectroscopy
In base configuration
1.1.7 Lateral force microscopy
In base configuration
Magnetic Force Microscopy*
1.1.1 Magnetic Force Microscopy
1.3
1.4
1.5
1.6
*
In base configuration
Scanning Tunneling Microscopy (STM)*
Requires STM probe holder
1.3.1 Constant current mode
With STM probe holder
1.3.2 Work function imaging
With STM probe holder
1.3.3 Density of state imaging
With STM probe holder
1.3.4 STM spectroscopy
With STM probe holder
Scanning current and capacitance probe micro- Requires special probe holder
scopy*
1.4.1 Scanning capacitance microscopy
With special probe holder
1.4.2 Kelvin Probe Microscopy
With special probe holder
1.4.3 Electric Force Microscopy
With special probe holder
1.4.4 Spreading Resistance Imaging
With special probe holder
Multipass techniques*
For the implementation of combined techniques
1.5.1 Two-pass techniques (АСМ+МСМ and etc)
Implemented
1.5.2 Constant Height mode (AFM, STM and etc)
Implemented
Lithography*
1.6.1 AFM Lithography in contact mode
Implemented
1.6.2 AFM Lithography in dynamic mode
Implemented
1.6.3 STM Lithography
Implemented
1.6.4 AFM Oxidation Lithography
Implemented
Probes and probe holders
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probe holders
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Basic information
1.7.2. Controller EG-3000
EG-3060/3060A controller designed to control the operation of scanning probe
optical or confocal microscope. The controller collects data from various sensors and
external devices and provides control outputs to the piezoelectric positioning devices, in
addition, all the gathered information is to be sent to the control computer for subsequent processing and visualization. Also, computer controls all parameters of movement and scanning. Exterior view of the controller is shown in Fig. 1.8:
Fig. 1.8 EG-3000 SPM controller.
For the control of positioning devices system uses a digital feedback and the original scheme for measuring capacitance displacement sensors, based on the TDC (time
to digital converter). Capacitance measurement is carried out in the scanning device and
controller receives a digital signal. Such a system increase accuracy and significantly
improve the device immunity.
Any of the signals available in the system can be used to operate the feedback of
the tip-sample distance. The controller keeps the feedback on the six channels simultaneously, which allows to scan by tip or by sample.
In order to implement the modulation technique microscopy (such as, for example, non-contact atomic force microscopy), controller provides dual-channel lock-in
amplifier, equipped with a highly stable master oscillator which is made on the basis of
the digital frequency synthesizer. High-speed digital data processing implemented using
programmable logic (FPGA), allows synchronous detection of signals at frequencies up
to 1.5 MHz.
Controller provides stepper motors control, allowing to connect from 4 to 12
drives in a micro stepping mode.
The device has additional analog inputs and outputs for connecting external
devices, as well as inputs and outputs for synchronization with external equipment.
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Basic information
USB interface is used for communication with the host computer. The controller is managed by the specialized software NSpec and EG3000 Dll.
EG-3000 detailed information is described in the manual: “SPM controller (model EG-3060 and EG-3060A)”.
1
1.1
Data sheet
General characteristics
1.1.1
CPU
1.1.2
PC Interface
1.1.3
Other interfaces
1.1.4
Size
1.2
32 bit; RISC
USB 2.0
RS 232, RS485, SYNC I/O
440 х 285 х 90 mm
High-voltage outputs
1.2.1
Voltage
1.2.2
Noise (RMS)
1.2.3
Number of channels
1.2.4
Resolution (digital-analog converters)
1.3
-10…150 V
< 5 ppm
6
18 bit
Stepper motors control unit
1.3.1
Number of channels
1.3.2
Power supply
24V, 3A
1.3.3
Microstepping mode support
1/16 step
1.4
4
Lock-in amplifier
1.4.1
Number of channels
2
1.4.2
Preamplifier gain
1-100
1.4.3
Input voltage range
±10 V
1.4.4
ADC resolution
16 bit
1.4.5
Frequency range of input signals
1.4.6
Frequency range of main oscillator
1.4.7
Output voltage amplitude
1.4.8
Frequency stability
1.4.9
Additional channels ADC / DAC
0-1,2 MHz
10 Hz – 3 MHz
10 mV-10 V
< 5 ppm
1.4.9.1 Number of input channels
4
1.4.9.2 Voltage range
±10 V
1.4.9.3 ADC resolution
16 bit
1.4.9.4 Number of output channels
2
1.4.9.5 Voltage range
±10 V
1.4.9.6 DAC resolution
16 bit
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Basic information
1.7.3. Certus Standard microscope base
The Certus Standard microscope base is used for placing SPM head Certus,
sample positioning and for optical microscope mounting and positioning.
A
Base plate
B
The installation location for the SPM head Certus
C
The platform for the installation and mounting of samples
D
The knobs for the sample stage positioning
E
The knob for the microscope arm mounting and positioning
F
The knob for the microscope vertical mounting and positioning
G
Tilted mounting for microscope
H
Microscope mount
I
The knobs for the horizontal microscope positioning
J
Retractable handle for the base transfer
Fig. 1.9 SPM Base Certus Standard.
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Basic information
1.7.4. Videomicroscope
Optical microscope with a digital camera is used for obtaining magnified images
of objects of study sites and for the images latching, SPM probe positioning relative to
the sample surface.
Optical microscope data sheet
1.1
Visualization
1.2
Magnification adjustment
1.3
Fine adjustment range
1.4
Image visualization
1.5
Illumination
1.6
Optical parameters
Digital video microscope
Manual
5 mm
Color digital video camera
Fiber illuminator
1.6.1 Numerical aperture
0.3
1.6.2 Camera sensor size
1/3”
1.6.3 Camera sensor resolution, px
1280x1024
1.6.4 Magnification
85x/1050x
1.6.5 View field
4.50/0.37 mm
1.6.6 Interface
USB
A
Microscope
B
Objective
C
CCD matrix camera
D
Illumination side port
Fig. 1.10 Videomicroscope
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Basic information
1.7.5. NSpec Software
NSpec software is used to control scanning probe microscope Certus Standard.
Basic functions:
•
•
•
•
•
SPM parameters adjustment;
optical system parameters adjustment;
scanning parameters adjustment;
scanning;
data processing.
The program is based on multythread kernel, written in C++ and built by compiler GCC4. The program interface is built using cross-platform libraries and libraries
QT4, QWT. The program is compatible with all current versions of OS Windows (XP,
2003, Vista, 7). Upon request, the program can be transferred to the operating system
Linux, * BSD, MacOS. Only basic functions of data processing are implemented to
NSpec software, and tools for optimal adjustment of scanning parameters. Specialized
software is recommended to use for full data processing, such as Gwyddion. For processing the spectral data is also recommended to use specialized programs such as
GRAMS. To facilitate the transfer of data to other applications NSpec program supplied
by the filters of import/ export formats ASCII, gwy (Gwyddion), spc (GRAMS).
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Operating principles
2. Operating principles
2.1.
SPM common principles
The Scanning Probe Microscope — the device for surface imaging and local
properties information.
In basic case Scanning Probe Microscope (fig. 2.1) includes:
• Probe;
• XYZ scanning/positioning system;
• Probe sensor for determination interaction with surface.
Fig. 2.1 SPM basic system.
The operation of a scanning probe microscope based on the principle of obtaining
information about the interaction of the probe to the surface at one point. At a small distance between the surface and the probe, one can fix the forces of interaction (repulsion,
attraction, and other forces) and the appearance of different effects (for example, tunneling of electrons). These interactions and effects can be detected with modern means of
registration. To register, use different types of sensors, whose sensitivity allows you to
record such disturbances. To construct a bitmap image uses a system of probe movement (scanning system) relative to the surface in XY or XYZ coordinates.
The recording system records the value of the parameter. The parameter value depending on interaction between the probe and the sample surface is recorded. The surface topography is constructed during scanning based on known or suspected dependen«Nano Scan Technologies Ltd.»
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Operating principles
cies of the interaction of the distance between the tip and the surface (3-D image in
XYZ coordinates).
Fig. 2.2 Common principles of SPM surface imaging.
The main difference between scanning probe microscopy techniques is in registration parameters and registration methods selecting.
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2.2.
Probe scanning/positioning
XY (XYZ) scanning process is used to get image in scanning probe microscopes.
2.2.1. Scanning
The scanning process proceeds as follows. The scanner performs a raster movement of the object (Fig 2.3). System takes signal measurement and digitizes data at
nodes of the raster to receive information about the surface characteristics. The direction
of lines along which scanner moves is called the fast scan direction. Perpendicular direction is called slow scan direction. The resulting image is based on the data obtained in
fast scan direction on forward or backward pass.
Fig. 2.3 Scanning process illustration.
One can write data on direct or on reverse the course of scanning producing a
shift in the perpendicular direction. In this case, the speed of image acquisition increases
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able, since for scanning probe microscopes there is difference between the surface profile at the forward and backward course because of the nonlinear properties of piezoelectric ceramics, and this is usually essential. Scanners with sensors also have a distinction between "direct" and "reverse" profile, although not always visible. This caused by
feedback errors in the direction of fast scanning. These errors are reduced with decreasing scanning speed. As a result, it often turns out that to obtain the desired image quality
is advantageous to use record data only on direct or reverse course.
2.2.2. Piezoelectric phenomena
All modern scanning probe microscopes, scanning/positioning systems, regardless of design, uses the inverse piezoelectric effect for positioning and movement.
Inverse piezoelectric effect – the effect of mechanical strain in dielectrics under
electric field. It occurs in crystals, which cells have no center of symmetry, resulting to
permanent electric dipole in the cells. When
applying external electric field for the such
crystal, occurs dipoles deformation, leading
to a change in crystal size.
Since the monocrystal growing of materials with piezoelectric properties is considerable difficulty, usually use polycrystalline materials – ceramics. In this ceramics
dipoles in the crystals are oriented predominantly in one direction of polarization in a
Fig. 2.2 Piezoelectric phenomena.
strong magnetic field. Accordingly, it
changes own size, caused by appearance of electric field (Fig.2.2).
Piezoelectric properties of the materials described by a set of piezoelectric constants. These constants describe relationships between applied voltage and material deformation. As a rule, even for a relatively small extension, high voltage should be attached to the material. For example, for lead titanate (PZT, Pb(Zr0,55Ti0,45)O3 with additions of Nb, Cr, La, Fe, etc.) piezoelectric constant d33=374×10-12 m/V (for PZT-5A).
To reduce the voltage control signal, serial connection of layers of piezoelectric
ceramics with electrodes on each layer are used (Fig. 2.3). In more advanced systems,
solid array of piezoelectric ceramics with electrodes in the piezostack body is used.
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Fig. 2.3 Piezostacks diagram.
2.2.3. Lever translation systems
In general, the displacement caused by the inverse piezoelectric effect, relative to
the size of the piezoceramic element is a very small amount. The strain usually does not
exceed 0.1% of total elongation of the device, displacement value is several tens of micrometers. To increase the displacement, variety of mechanical devices such as levers,
hinges (Fig. 2.4), and bending devices (Fig. 2.5) are used.
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A
Piezo stack.
B
Elastic Point.
C
Lever.
A
Piezo stack.
B
Bulk.
Fig. 2.4 Bending displacement system diagram.
Fig. 2.5 Bending displacement system diagram.
Typically, the piezoelectric driving element is used only for forward movement.
The used material is subjected to Hooke's law in the range of applied loads, i. e. the
strain is directly proportional to the applied voltage. The material of the device undergoes only elastic deformation. As a result, after the termination of the external force elements of a such system take initial size, shape and, accordingly, the position in space.
This fact is used for backward movement.
In the real devices scanner elements are combined to build kinematic structure for
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plane-parallel movement in XY plane or XYZ space.
2.2.4. Displacement sensors
Because of the nonlinear properties of piezoelectric ceramics, obtained image
contains distortions. It is important to understand features of the dependence between
the control electric field and the deformation of the piezoceramic sample, namely,
non-linearity and ambiguity of this relationship. Usually, the nonlinear properties of
ceramics are divided into creep, hysteresis and non-linearity itself. Also nonlinear properties includes volatility and sensitivity of the piezoceramic. Non-linearity and ambiguity of the dependence of the control voltage – the situation often leads to significant distortions of the image.
For the correction of displacement, many types of displacement sensors can be
used. It can be optical, inductive, magneto, capacitor, etc. Capacitive sensors are used in
the two-dimensional scanning stage Ratis and in SPM head Certus. The operating principle of such sensors are displayed in Figure 2.6.
Fig. 2.6 Capacitance sensors diagram.
Since, the capacity of a flat capacitor consisting of two parallel plates is given by
2.1:
С= 0
S
d
(2.1)
C – capacitance, S – capacitance plates square, d – plate distance, ε – dielectric factor,
ε0 – dielectric constant. When the distance between the plates changes the sensor capacitance, offset of the axis can be measured.
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2.3.
Probes
2.3.1. Basic probe parameters
The main element of any scanning probe microscope is the probe. Based on the
interaction of the probe and the surface, image of the surface is constructed and the distribution on the surface of local physical characteristics.
In general, a scanning probe microscope is a conical needle or pyramidal shape.
The most common material for the probes are metals (tungsten, platinum, and similar to
scanning tunneling microscopy), silicon and silicon nitride Si 3N4 – for atomic force microscopy. Silica coated for magnetic and conducting techniques, silicon with a diamond
coating for indentation, etc. General view of the probes is shown in Figure 2.7.
A
Probe body.
B
Coating.
R
Tip curvature.
H
Tip Height.
Cone angle.
Fig. 2.7 Probe drawing.
Resolution and accuracy of surface elements mapping depends on the probe
corner radius and the cone angle. Maximum height difference on the surface available
for display depends on height of the probe. Coverage probes allow to use of various
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techniques of scanning probe microscopy.
In addition to these parameters on the quality of the image, a set of techniques
and the ability to study samples of different nature is influenced by two parameters. This
is the probe stiffness or the force constant (N / m) and the probe resonant frequency
(resonant frequency, kHz).
2.3.2. Probe drawings
In general, probes for scanning probe microscopy can be a needle, but using industrial lithography and various coating methods, the probes cab be made with specialized forms (Fig. 2.8).
A Chip
B Bulk
С Tip
D Cantilever with rectangular
bulk
E Cantilever with triangular
bulk
F SEM tip image
Fig. 2.8 Cantilever tip drawings and images.
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2.4.
Cantilever Z position detection system
Different registration systems are using to register the movement of the probe and
its position relative to the surface. For atomic force microscopy, two types of registration systems are using.
2.4.1. Deflector registration system.
The most common registration system based on laser deflectometer. Schematic
diagram of the system shown in Fig. 2.9.
A
Tip.
A1
Deflection of cantilever bulk.
B
Laser.
C
PSD (Position Sensitive Diode) with 4 sensitive areas
D
Sample.
E
PSD image. Sections is marked A, B, C, D.
F1
Laser spot position at PSD center.
F2
Random laser spot position at PSD.
Fig. 2.9 Deflectometer scheme.
The laser beam is focused on the probe bulk. The reflected beam falls on the 4cell photodiode. By the ratio of the intensity in the photodiode sections, position of the
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reflecting probe part in space is determined. When the probe is moved along Z axis or
beam is rotated, laser spot position is changed on the photodiode. As a result, the probe
position relative to the surface according to predetermined relationships.
In the scanning probe microscope Certus registration system based on laser deflectometer shown in Fig. 2.10.
A
PSD with 4 cells.
B
Probe (cantilever).
С
Laser beam.
D
Probe holder and scanner.
Fig. 2.10 Deflectometer system in the SPM Certus head
Fig. 2.11 PSD with laser spot.
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2.4.2. “Shear-force” registration system
The "shear-force" method is based on recording changes in the oscillation frequency of the probe caused by the tangential component of interaction forces between
the probe and the surface. To determine changes in frequency are used tuning-fork resonators type (tuning-fork, Fig. 2.12). Resonators vibrations are detected by a direct
piezoelectric effect of quartz crystals.
A
Probe tip.
B
Probe.
C
Electrodes that are used to measure voltage changes occurring on the sides of a quartz crystal (direct
piezoelectric effect) due to changes in frequency during the interaction with the surface.
D
Quartz crystal (piezoelectric).
E
Piezoelectric Driver. Used to create a forced oscillation of the resonator (set the initial vibrations).
Fig. 2.12 “Shear-force” registration system.
This registration method is used where need to avoid interaction of the sample
substance with a laser radiation, or in near-field microscopy systems.
There is a special probe holder for tuning-fork type probes. For the near-field
scanning optical microscopy special near-field tip is mounted on the tuning-fork instead
of scanning tip (Figure 2.13).
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A
«Tuning-fork» type probe
B
Probe holder
C
NSOM fiber.
D
Certus SPM head
Fig. 2.13 “Shear-force” registration system.
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2.5.
Feedback
To generate the control signal is commonly used proportional-integral-differential
(PID) controller (see the scheme 2.14) in the feedback loop of a scanning probe microscopes. PID controller generates a control signal based on the components of the proportional signal, the integral of the input signal and the derivative of the input signal.
P
Proportional component of the signal is proportional to set point error.
I
Integral component is used to smooth out the statistical errors in the input signal.
D
Differential component needed to predict the controlled variable deviations.
Setpoint
Error
Set value of the controlled variable.
Difference between the actual and set value of the controlled variable.
Process
Controlled process.
Output
Output form the process sensor.
+/-
Sign of the term to calculate the difference between the actual and set value for actual value.
Fig. 2.14 PID control.
2.6.
Combining optical and scanning probe microscope
The scanning probe microscopy has some drawbacks: accurate probe positioning
to the sample surface point, selecting of field of a surface of interest from the scientific
point of view, combining optical and topographical information about examinee surface.
To overcome this lack combine a scanning probe microscope with an optical one.
Optical microscopy techniques allow to select required surface field, to move the probe
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to this field and to perform scanning.
A
Optical image of the examinee and the cantilever.
B
SPM image of the examinee on the surface (topography).
Fig. 2.15 Combination of the optical and scanning probe microscopes.
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3. Start operation
3.1.
SPM Certus Standard installation
The sequence of commissioning SPM Certus Standard includes following steps:
1
Installation of the vibrating protection
2
Installation of the SPM Certus Standard base and videomicroscope
3
Installation of the SPM Certus
4
Connection to the computer
3.2.
Installation of vibration protection
Depending on the chosen configuration can be installed both passive, and active
vibrating protection. It should be installed on chosen SPM Certus Standard installation
site before installation and microscope connection.
In case of use of active vibrating protection it is necessary to use the installation
instruction for the chosen model.
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3.3.
Installation SPM Certus Standard base and videomicroscope
A
Installation of the base plate
B
Installation of the stand
C
Installation of the arm
D
Installation of the microscope mover
E
Installation of the videomicroscope
Fig. 3.1 Microscope base installation steps.
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3.3.1. Installation of the stand
A
The slot for stand mounting
B
The holes for stand mounting screws
Fig. 3.2 Installation of the stand on the base.
3.3.2. Installation of the arm
A
Arm fixation knob
Fig. 3.3 Installation of the arm
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3.3.3. Installation of the microscope mover
A
Slots for the top screws
B
Slots for the top screws
Fig. 3.4 Installation of the microscope mover.
The microscope mover fastens to an arm on 4 screws. The top screws are established from mover face sheet. The bottom motions from the back party. For installation
of the bottom screws it is necessary to transfer a mover in extreme bottom position.
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3.3.4. Installation of the videomicroscope
A
Installation of the holder ring
B
Installation of the cover
C
Installation of the microscope mover
Fig. 3.5 Installing the microscope on the mover.
At microscope installation it is necessary to fix the holder ring on a microscope,
to put a cover on a holder ring and to install a microscope with a holder ring and a cover
in a microscope mover. The cover is fixed on a mover by three screws.
If necessary the illumination device is connected to a microscope. At connection
of the illumination device it is necessary to use the instruction applied on this device.
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3.4.
SPM Certus installation
Installation of the SPM Certus requires scanning head Certus, SPM controller
series EG-3000, the probes holder, cable kit and computer.
3.4.1. SPM Certus head description
Initially, you must arrange scanning head on a hard flat surface (Fig. 3.1).
A
XYZ scanning system.
B
Stepping motors.
C
Stepping motors cables
D
Knobs for laser beam to cantilever bulk alignment.
E
Knobs for reflected laser beam to PSD diode alignment.
Fig. 3.6 Certus scanning head.
Stepping motors connectors from the SPM head side:
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A
Cable connector for two side-stepper motors. At one connector there are two cables.
B
Rear stepping motor cable connector. At one end is a single cable.
C
Appearance of the stepper motors cables and connectors
Fig. 3.7 Stepping motors connectors.
Additionally, the SPM head Certus needs to connect cables for high voltage signals and digital interface, analog signals cable and power (Fig. 3.8).
Fig. 3.8 Scanning head signals cable.
Additional cables are connected to the back side of the head (Fig. 3.9).
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A
High voltage cable and digital interface cable.
B
Analog signals cable and power.
Fig. 3.9 Cable connections diagram.
Fig. 3.10 Scanning head cables connection.
Cable plugs are designed the way that allows them to join up just in one direction.
For this purpose it's required to nest the plug into the socket and wheel smoothly turning
it define the lay to enter it.
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Fig. 3.11 Scanning head with connected cables.
Probe holder connector is located at right head side (Fig. 3.7). Probe holder plug
connects to a similar manner.
Fig. 3.12 Connector for the probe holder.
3.4.2. Probe holder connection
Probe holder must be connected to scanning head(Fig. 3.13). Regardless of the
scanning probe microscope mode, the principle of holder connecting is the same.
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Fig. 3.13 Probe holder.
The holder is attached to SPM head with magnetic tablets. Appropriate mounting
is located on the head bottom side. To fix the probes holder it is necessary to move to
the corresponding fastening the SPM head and install the appropriate slot.
To prevent damage of the probes after their installation it is recommended initially install the holder on the AFM head, and then connect the plug to the jack on the
head (Fig. 3.9).
Fig. 3.14 Probe holder mounting.
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3.4.3. Installation SPM Certus on the base
Fig. 3.15 Installation SPM Certus on the base.
Installation of the SPM head Certus on the base can be spent in two ways. In the
first way, the optical microscope remains in working position. The SPM head needs to
be got for an optical microscope and to establish on seats on the base. In the second
way, the optical microscope is tilted back in non-working position, and SPM is put on
seats then the optical microscope is came back in a working position.
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3.5.
EG-3000 controller connection
After connecting all cables and probe holder installation, scanning head must be
connected to SPM controller EG-3000 series.
Pin and connectors description are given in Figure 3.15. A complete description
of the connectors on the controller front panel there is in the SPM controller EG-3000
User Guide.
A
Piezo stacks high voltage and displacement sensors digital interface.
B
Supply voltage and analog signals.
C
Back stepping motor connector.
D
Side stepping motors connector.
Fig. 3.15 Сertus scanning head and EG-3000 controller correspondents.
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3.6.
PC connection
After scanning head connection to the controller, it is needed to connect the USB
controller to your computer. Certus scanning head has no direct connection to the computer. In this case, the computer must have installed software to control SPM system,
and USB driver.
3.7.
Videocamera connection to the computer
The microscope videocamera is connected to the computer with USB. For camera
connection it is necessary to connect a cable to the camera and the computer, to install
camera drivers.
3.8.
Remote controller connection
If the delivery complete set includes the additional remote control device for SPM
Certus Standard manipulation – it is necessary to connect it to the computer with USB
and to establish the necessary software.
Fig. 3.16 Remote control device for SPM Certus Standard.
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3.9.
NSpec software installation
Before working with the program NSpec, an archive containing the program files,
you need to unzip to a local or removable drive.
Installation is not required. The program runs directly from the *. exe file. To
work with the program is to start by double clicking the left mouse button or file nst.
exe or NSpec_№. exe in the folder Soft_Package_ №. The example in Fig. 3.17. When
you run nst. exe or NSpec_ №. exe will run the program (Figure 3.18). After performing the above action, main window NSpec displays. Following the withdrawal of the
main window on the screen you can start working with the program and connected
equipment.
Fig. 3.17 NSpec starting.
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Fig. 3.18 NSpec is starting.
3.10. SPM Certus Standard «on/off» regulation
3.10.1.
«On» rules
• Turn PC power «On»;
• Run PC;
• Run NSpec software;
• Turn controller power «On»;
• Check system functionality.
In the case of correct connection of the controller, in the upper right corner of the
main window NSpec SPM controller connection indicator appears as
The indicators on the front of the SPM controller means:
1
PWR
Power indicator
2
USB
USB data transfer indicator
3
FNC
Service indicator
4
RDY
Stand By indicator
5
SCN
Scan indicator
6
FB
SPM Feedback status indicator
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3.10.2.
•
•
•
•
•
«Off» rules
Stop scanning;
Save data (if needed);
Move up scanning head from sample to avoid tip damage.
Close NSpec software;
Turn controller power «Off».
3.11. NSpec basic options
For program interface tuning is used Options unit, that is located on the basic instruments panel
. After pressing this button program options window appears.
Fig. 3.19 NSpec user interface options.
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For SPM Certus Standard properly working required following options:
Interface language
Interface language combo box
Buttons size
Interface buttons size (px)
Select font
Calls “Select font” standard dialog
Show data window
Data unit on/off check box
Show scan window
Scan unit on/off check box
Show SPM options window
SPM unit on/off check box
Show oscilloscope window
Oscilloscope unit on/off check box
Show lithography window
Lithography unit on/off check box
Show scan (Head) window
Scanning by head tab in the Scan unit on/off check box
Show scan (Stage) window
Scanning by stage tab in the Scan unit on/off check box
Show oscilloscope calibration
Oscilloscope calibration window on/off check box
Show head calibration window
Scanning head calibration tab in the Oscilloscope unit on/off check
box
Show stage calibration window
Scanning stage calibration tab in the Oscilloscope unit on/off check
box
Show video window
Video unit on/off check box
Enable auto-send to Data from Scan
Auto-send obtained data to the Data unit on/off check box
Enable Sensors autocalibration on start
Sensors autocalibration with device start on/off check box
Enable Optics initialization start
Optics initialization with device start on/off check box
Enable PID autocalibration on start
PID autocalibration with device start on/off check box
Data auto-save time, min
Sets data auto-save interval in the Data unit. If 0 – auto-save disabled
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Fig. 3.20 NSpec after adjustment for working with SPM Certus Standard.
Below options determines by user choice
Enable auto-send to Data from Scan
Auto-send obtained data to the Data unit on/off check box
Enable Sensors autocalibration on start
Sensors autocalibration with device start on/off check box
Enable PID autocalibration on start
PID autocalibration with device start on/off check box
Data auto-save time, min
Sets data auto-save interval in the Data unit. If 0 – auto-save disabled
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4. Working with SPM Certus Standard
In this section work with scanning probe microscope Certus Standard in a
semi-contact atomic force microscope mode is described. For other AFM modes look
the user manual additions. Before reading this section it is recommended to familiarize
with the user's guide the software NSpec. To start work it is necessary to switch SPM
Certus Standard on.
4.1.
The list of base operating modes
It is possible to allocate following basic modes:
Обозначение
Описание
SPM modes
Optical microscopy modes
Superposed modes
The full list of base operating modes:
SPM modes — probe scanning
+
+
-
Optical microscopy modes
-
+
+
* The scanning stage is used only for positioning of samples
4.2.
Basic SPM Certus Standard operations (atomic-force microscope
techniques)
For getting of SPM images it is necessary to adjust an atomic-force microscope.
The general sequence of actions on SPM adjustment:
Adjustment of range and bias of the capacity sensors
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Piezoscanner calibration
Operation isn't obligatory, there is an automatic and
manual mode of adjustment
Capacity sensors calibration
Operation isn't obligatory, there is an automatic and
manual mode of adjustment
Adjustment of PID control
Operation isn't obligatory, there is an automatic and
manual mode of adjustment
Probe installation
Required
Adjustment of deflection system
Required
Adjustment of feedback system
Required
Adjustment of feedback setpoint
Required
Preliminary positioning of samples
If necessary
Probe landing
Required
Sample positioning
If necessary
Preliminary scanning
Operation isn't obligatory. It is required for samples
with unknown parameters
Correcting of the scanning parameters
Operation isn't obligatory. It is required for samples
with unknown parameters
Scanning
If necessary
Primary data treatment and saving
If necessary
Probe lifting
Required
4.3.
Adjustment of range and bias of the capacity sensors
Each time the SPM Certus Standard switch on and software NSpec occurs automatic adjustment of range and bias of capacitor sensors. The automatic adjustment option is switched in
window with Enable Sensors autocalibration on start
check box.
In case of automatic recalibration is needed or for manual mode calibration it is
required to press Show/hide calibration window
in the Oscilloscope unit. After
pressing the button the calibration instruments arises. Press Run capacitance sensors
auto adjustment
button for automatic calibration executing. After pressing this
button sensors auto adjustment will start.
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Fig. 4.1 Oscilloscope unit in calibration mode drawing.
4.4.
Adjustment of PID control
Each time the SPM Certus Standard switch on and software NSpec occurs automatic tuning of PID control. The automatic adjustment option is switched in
window with Enable PID autotuning on start check box. In case of automatic calibration needs iteratively or in manual mode it is required to press Show/hide calibration
window
in the Oscilloscope unit. After pressing the button the calibration instru-
ments arises.
For automatic tuning executing requires to press PID autotuning
button.
After pressing this button scanning head PID control auto adjustment will start.
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4.5.
Probe installation
Before you start, you must install the probe into the probe holder as shown in Figure 4.2.
Fig. 4.2 Probe holder.
Probes or cantilevers are stored either in the form of plates on which it to break
off before the work of individual probes, or already prepared for work in special containers (Fig. 4.3). Usually, cantilevers tips directed toward the cover package.
Fig. 4.3 Cantilevers in gel-pack boxes.
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Fig. 4.4 Cantilever mounting to holder.
Installation procedure:
• use tweezers to capture probe for the side surfaces so that the bulk with the
tip was directed toward the hand;
• probe holders have to be turned over and pressed to the surface to reveal
clip so that the button was pressed on the upper side of the probe holder
(Fig.4.4);
• Mount probe to holder;
• Release the probe fix button;
• Mount probe holder to scanning head with p.3.4.2.
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A
Probe.
B
Spring knob.
Fig. 4.5 Probe mounting.
4.6.
Sample mounting
The SPM Certus Standard allows to operate with samples satisfying the following
dimensions:
min
Any
max without SPM
Up to Ø 230 mm and 30 mm height.
max with SPM
Up to Ø 125 mm and 16 mm height.
Samples should be fixed to special polycrystalline sapphire substrates, which are
contained in the hardware set of the instrument. Dimensions of these substrates are
24х19х0.5 mm. Fastening of the sample to the substrate can be done by using doublesided scotch tape or glue.
When mounting the substrate with samples on the sample stage, the substrate is
put on the sample platform (see Fig. 1.9, point C) and pressed by spring clips (Fig 4.6).
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Fig. 4.6 Sample fixed on the substrate, which is mounted on the stage.
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4.7.
Information about NSpec software required for SPM Certus Standard
adjustment
To entry SPM window press the button
, that is situated on the top panel
of the NSpec window.
Key parameters of adjustment a scanning probe microscope are located in the
SPM window. In the SPM window feedback parameters are set, stepper motor are controlled, scanning mode are set and etc.
Fig. 4.7 SPM window drawing.
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4.7.1. Plot mode control
In the left part of a window there is a panel of Plot mode control. It is used for
display resonant curve and others signals received by system from sensors and a digital
microscope.
Fig. 4.8 Plot mode control.
Frequency curve mode
A field of the probe amplitude-frequency curve is displayed in the right
window part.
Oscilloscope mode
An oscilloscope field is displayed in the right window part. There are aver age and RMS of selected signal values fields under oscilloscope curve.
Spectroscopy mode
A land/lift curves, Z spectroscopy and spectroscopy parameters panel are
displayed in the right window part.
4.7.2. Cantilever resonant frequency acquisition
Fig. 4.9 Cantilever resonant frequency acquisition.
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The signal for plotting the frequency curve is selected in the Channel combo box
on the Frequency scan panel. In the near fields the frequencies range is completely set.
By default, in the Channel combo box is selected signal Mag used for reception of resonant frequency of probes.
Fig. 4.10 Signals available for the frequency curve.
The button
performs frequency scanning. The nearby progress bar shows
scanning complete progress with percents. The current resonant frequency value is displayed on the Current frequency slider. It can be set in other value if necessary. The
Drive intensity slider controls probe piezodrive output voltage.
4.7.3. Oscilloscope mode
Fig. 4.11 Oscilloscope plot window.
An average value of the signal magnitude is displayed in the Average, V field. A
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root mean square of the signal is displayed in the RMS, V field. In the T, s field sets a
time interval.
4.7.4. Land/lift curves
Fig. 4.12 Z spectroscopy curve.
The red strip displays current position of probe Z0, and two dark blue strips display limits of construction of a curve and correspond to positions Z0-Z1 and Z0+Z2. At
construction the curve probe moves to point Z0+Z2 then moves downwards to point Z0Z1, further it makes movement in the opposite direction and comes back to an initial position. The slider <--ΔZ1, μm sets start position Z0-Z1. The slider ΔZ2-->, μm sets final
position Z0+Z2. It is also possible to set start and final position value in the fields
nearby the sliders. After typing-in the number value from the keyboard press the button
Enter Key.
In the Channel combo box it is necessary to selected signal for curve acquisition.
The Points combo box sets a number of curve points. In the Speed, nm/sec field it is
possible to set curve scanning speed. The button
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4.8.
Deflectometer system adjustment
Initially, you must configure the system of probe deflection. To do this:
• Align laser beam to cantilever bulk;
• Align reflected from bulk beam approximately to PSD center;
• Find appropriate parameters for resonant mode;
• Ger probe resonant curve.
4.8.1. Laser beam alignment to cantilever bulk
Procedure:
• Open SPM window in NSpec software;
• Define current system configuration. Two different choices is shown at
fig.4.5
• Align laser beam to cantilever bulk.
a)
b)
Fig. 4.13 а) Not aligned system; b) Aligned system.
In the case of fully disaligned registration system, laser beam may come out cantilever bulk or come to the probe holder
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a)
b)
Fig. 4.14 а) out of cantilever chip; b) Laser spot located at holder.
In this case, using the positioning screws, make coinsidience laser beam with cantilever bulk
Fig. 4.15 Compliance of the direction of rotation with direction of laser spot travel.
When the laser beam hit on the cantilever bulk, the diffraction pattern will be
clearly visible.
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Fig. 4.16 Laser beam aligned to bulk and diffraction pattern is clearly visible.
4.8.2. PSD (position sensor diode) alignment
You have to align reflected laser beam from bulk with center PSD, to do this you
can use PSD positioning screws.
Fig. 4.17 Compliance of the direction of rotation with direction of PSD travel.
SPM Feed Back window shows laser spot position at PSD and it's intensity.
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б)
a)
Fig. 4.18 a) reflected beam is out of PSD; b) laser beam is within PSD area.
4.8.3. Search of the reflected beam
Once the SPM Feed Back window will display the signal from the photodiode it
is necessary to find the maximum reflection from the bulk. Red sphere size corresponds
to laser spot position and its intensity, during alignment must be on a blue field (PSD
area)
Fig. 4.19 PSD signal.
Using laser beam alignment screws, try to get signal maximum.
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Fig. 4.20 Signal maximum.
4.8.4. Alignment the reflected beam with the PSD center
After finding the maximum of the reflected signal it is necessary to combine the
laser spot center to the photodiode center. To do this, use the photodiode positioning
screws to move the laser spot in the center of the SPM Feed Back window and obtain
close to zero values of indicators DFL and LFL as possible. (Figure 4.21).
In the drop-down menu beneath the SPM Feed Back should be set OFF.
Fig. 4.21 Laser Beam is in the PSD center.
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4.8.5. Probe resonant frequency acquisition
After finding the maximum of the reflected signal and overlapping centers of the
laser spot and the photodiode, in the case of contact mode, you can proceed to feedback
parameters settings and approach of the probe to the surface. In the case of non-contact
methods, you should find the resonant frequency of the cantilever. For non-contact
methods in the field FB Input Signal (SPM Mode) must be set to Probe Magnitude –
Tapping Mode.
To do this:
• choose the MAG in Channel combo box in the Scan window SPM (Fig.
4.22);
• set the frequency search range from 0 to 500 kHz (or greater in the case of
use cantilevers with a large resonant frequency);
• set all multiplier Input Gains is equal to 1;
• set Drive Intensity slider value is equal to 1;
• press Run.
Fig. 4.22 Probe resonant data.
After that, Plot will show the current resonant curve of the cantilever (Figure
4.23). If you know roughly the resonance frequency value of the cantilever, search
range can be narrowed (Figure 4.24). If necessary, resonant frequency can be set manually (Figure 4.25), using obtained resonant curve.
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Fig. 4.23 Cantilever resonant frequency acquisition.
Fig. 4.24 Cantilever resonant frequency acquisition.
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Fig. 4.24 Manual chose of the cantilever driver frequency.
You have to achieve the resonant magnitude of 1 V in the absence of information
about the sample properties. Take this value as reference value.
4.9.
Feedback parameters
The Feedback panel contains a field of display of laser reflected from a cantilever beam signal strength, elements of management of the laser, and also elements of
management of feedback system.
On a blue field intensity of the laser reflected from a cantilever beam to the foursection photo diode is displayed by a red stain. Position of a stain in a midfield means
that the stain from the laser is in the central part of the four-section photo diode, thus
values of DFL and LFL signals have values zero or close to zero values.
In the left bottom corner of the blue field the laser intensity signal INT is displayed. INT Value is comparable to the sizes of a red stain. FB Z means the device carrying out feedback (by scan stage or head). In the right bottom corner the Mag signal
value is displayed. There is head scanner Z position bar in the right top corner. Green
color corresponds to a safe approach of a probe, and red means that the probe is too
close to the sample and there is a probe damage possibility.
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Fig. 4.25 SPM Feedback panel.
SPM laser on/off
SPM laser on/off button.
Show PID parameters
The button causes displaying feedback Integral, Differential and
Proportional components and Setpoint.
Feedback sign
The button changes feedback sign.
Feedback on/off
The feedback on/off switch button.
Feedback by head/stage
Switching head/stage Z scanner for caring out the feedback.
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Set the feedback input signal and the relevant scan mode in the combo box.
Fig. 4.27 Choosing feedback input signal.
The automatic landing state indicators are shown in this window additionally.
Landing complete
The probe has landed to the surface.
Move tip down/up
Launches landing or lifting the probe to the sample.
Lower/upper limiter
Lower/upper limiter has reached.
When choosing microscope type Snotra in a stepper motors options menu it will be
running in a resonance microscopy mode using quartz resonators – Tuning-fork (TF
mode).
Fig. 4.28 Switching in a resonance microscopy mode using quartz resonators.
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4.9.1. Additional scan parameters
Fig. 4.29 Additional scan parameters panel.
Gain factors for the DFL, LFL, Int signals are established in the corresponding
combo box. The frequency of the low-pass filter are established by corresponding slider
and entry field. The phase shift for lock-in phase detector are established by corresponding slider and entry field. It is also possible to set the value in the fields nearby the
sliders. After typing-in the number value from the keyboard press the button Enter Key.
4.9.2. General recommendations of feedback parameters
If you have no information about surface properties it is recommended to set all
gains equal to 1 by corresponding sliders. After prior image analysis adjust feedback
parameters.
Feedback maximum gains are determined by starting the feedback loop instability. It looks as a noise with high amplitude and high frequency in the feedback controlled signal. Instability can occurs under same parameters with others samples. For
each sample feedback parameters have to be established individually. Than "more
softly"sample surface and the high difference of heights, the feedback parameters
should be larger. The same advice concerns the noise and influence of the outer vibrations. For this purpose require to regulate Proportional and Integral gains. Its optimal ratio is around 10:1. For “hard” material and low difference of heights (about some tens of
nm) feedback gains may be established closer to zero, for example, 0,1-0,3.
For high speed scanning it is recommended to establish gains equal-to-or-greater-than 1. Closer to value, when instability has started.
4.9.3. Setpoint tuning
After setting the resonant frequency and amplitude, and tuning feedback parameters, set up the setpoint value in the relevant input field using MAG value. For the as-
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sessment scan it is recommended to install feedback value to 50% of current MAG
value. Normally, this value is depends on the surface sample characteristics.
4.9.4. Probe Z axes control
There is a probe Z position slider in the left upper corner of the SPM window for
setting up current probe Z position. To set up Z probe position using keyboard type
value in the input field and press Enter key.
Fig. 4.30 Probe Z control slider.
4.10. Sample stage positioning
Firstly the sample should be placed on the stage and, if necessary, mounted.
A
Stage with sample holders
B
Sample X positioning screw
С
Sample Y positioning screw
Fig. 4.31 Sample stage.
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Two screws are designed to sample stage positioning.
A
Sample X positioning screw
B
Sample Y positioning screw
Fig. 4.32 4.9. Sample stage positioning.
4.11. Probe approaching to the sample
Stepper motors perform the probe approaching to the sample surface. The control
of the stepper motors is carried out by the NSpec program or by the remote controller.
4.11.1.
The control of the stepper motors
There is a Motors control panel in the left part a window.
Fig. 4.33 Motors control panel drawing.
This instrument panel are used to control and operate with the stepper motors.
The motors are utilized for automatic approaching the tip to the sample by moving
down scanning head.
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Move up
By pressing this button movement of stepper motors upwards
with the set speed on the set distance is carried out.
Move down
By pressing this button movement of stepper motors downwards with the set speed on the set distance is carried out.
Fast movement
By pressing this button movement of stepper motors upwards
upwards to limit
with the set speed to limit switch is carried out.
switch
Fast movement
By pressing this button movement of stepper motors downdownwards to limit
wards with the set speed to limit switch is carried out.
switch
Landing
By pressing this button automatic approaching is carried out.
Step up
By pressing this button stepper motors perform one step up
Step down
By pressing this button stepper motors perform one step
down.
Motor options
This button invokes motor options window
Control for each Switching in the each motor control mode.
motor
Not available with Certus Light device.
Shuttle options
This button invokes remote control properties window.
Fig. 4.34 Drawing of the motors control panel in the each motor control mode.
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4.11.2.
Stepper motors settings
By pressing the button
additional Motors options window is opened.
Fig. 5.11 Motor options window.
In the Device type combo box you can choose «Nano Scan Technologies Ltd.»
microscope configuration that you have.
Fig. 4.35 Choosing microscope configuration.
In the Up moving options the Speed (up 0 to 1000 μm/s) and the Distance (up 0
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to 1000 mm) for upward moving are set up. In a similar way set up options for downward moving. With One step options sets the values of the motors step in relevant directions for One Step Up
and One Step Down
button.
In the Landing options parameters of automatic approach by
button
are set up. Landing mode means:
Mode 1 – the approach is carried out by only one motor (rear motor, № 3);
Mode 2 – the approach is carried out by three motors.
The Speed (μм/сек, 0…1000) in the Motor level options means the motor speed
when Fast movement upwards (downwards) to limit switch buttons pressed.
On the Calibrations panel parameters of stepper motor calibration are set. In the
field the Thread pitch (mm) is set a thread pitch. In the Step number field is set full
quantity of steps.
4.11.3.
Remote control adjustment
The Remote control
button calls remote control adjustment window.
Fig. 4.36 Remote control GUI.
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Mechanical Z-mover motion
Shuttle controls lens mechanical mover.
Piezo Z-mover motion
Shuttle controls lens piezo mover.
Control 3 motors together
Shuttle controls stepper motors together.
Control first motor
Shuttle controls stepper motors number 1
Control second motor
Shuttle controls stepper motors number 2.
Control third motor
Shuttle controls stepper motors number 3.
Run approach
Start/stop head soft approach.
Other functions keys
Keys for other device and functions controlling.
Tabs All motors and Motor 1 ÷ 4 are contained control options by the joystick.
Steps — number of steps on one turn of a wheel for stepper moving. Speed — number
of steps in a second at turn of a shuttle for fast movement on the first position. Speed
Multipliers for shuttle positions-multipliers on which speed increases at installation of
a shuttle for fast moving by the chosen position.
For control from the program devices operated the joystick it is necessary to
guide the cursor at a wheel of management (it is shown on the figures more low) and to
move to the necessary position. For a stop of movement it is required to return a wheel
of management in former position.
Fig. 4.37 Shuttle fast moving.
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Fig. 4.38 Wheel for step-by-step moving.
4.11.4.
•
•
•
•
Tip approaching
The approach of a probe to a sample surface consists of following actions:
head leveling;
head tilting;
coarse approaching;
fine approaching.
4.11.5.
Head leveling
After probe installation it is necessary for leveling scanning head Certus. For this
purpose press the button Fast movement upwards to limit switch
. Thus three
motors run together and a scanning head will be lifted in the maximum position and will
accept horizontal position.
The given operation needs to be repeated after probes replacement. After scanning there is no necessity to translate a scanning head in extreme top position. It is
enough to take away SPM from a surface on convenient for work and safe for a probe
distance.
4.11.6.
Head tilting and coarse approaching
In some cases it is recommended to scan with the probe tilted at a certain angle to
the surface, or to compensate for the slope of the surface samples. It's allow to minimize
contact spot area of the tip with the surface. To do this, use individual control of each
stepper motor. The algorithm is:
• Move down head on the 5-10 mm from the top position by button Fast
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movement downwards to limit switch
;
• For a stop of movement it is necessary to press this button repeatedly;
• Go to the stepper each motors control mode
;
• Move up to maximum rear motor;
• Return to the option of all motors control
;
• Start rough approach to sample by button Fast movement downwards to
limit switch
.
Use rough approach till approximately 3-5 mm from the surface. Decrease approach speed for closer distance.
4.11.7.
Fine approaching
After a coarse approach has complete it is necessary to switch on feedback by
Feedback on/off
and to run landing by
. Upon reaching the surface,
and the magnitude of the probe oscillations equal to the specified by Setpoint value approach process will stop. Next, it is need to verify the absence of oscillations. Switch to
Oscilloscope mode in the Plot Mode Control (Section 4.1 details. software NSpec
manual).
4.11.8.
Approaching by remote controller.
All operations on control of stepper motors and feedback are duplicated on buttons of the remote controller.
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4.12. Sample positioning
If after a head approach to a surface there is a necessity of sample positioning it is
necessary to switch off feedback by the button Feedback on/off
. After switching-
off of feedback there will be an automatic lift of a probe from a surface on safe distance.
After positioning of the sample it is necessary to switch on again feedback and to run
fine approach if necessary.
4.13. Adjustment of scan parameters
After tip landing to the surface, open Scan
window. In the Scan tab
scan key parameters, such as number of image points, its sizes, a scanning direction,
scanning speed and others, are presented. Four fields for displaying of the received data
are located in the central part of the Scan window.
Fig. 4.39 Scan window drawing.
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Fig. 4.40 Scan parameters.
Nx size
Points number of in X scan direction.
Ny size
Points number of in X scan direction
Scan width, μm
Scan width in μm. Scan width and height field are active only when the Area selection
Scan height, μм
button has pressed.
Scan height in μm. Scan width and height field are active only when the Area
selection
button has pressed.
Channel A and B
The signals received in forward scan direction are selected in the combo box
Channel C and D
The signals received in backward scan direction are selected in the combo box
Section
The check box for cut section construction for relevant channel. The title color is
relevant to the cut section color.
Velocity, Hz
The slider sets a scan velocity. A scan velocity value also can be set in the edit
field near the slider (press Enter key after changing the value).
Above the Velocity slider scan complete percents are displayed.
Lift mode
Enables double-pass scan techniques.
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Disables double-pass scan techniques.
Directions
Combo box for scan direction choosing. The arrow means fast scan direction.
Along X axes, from upper left corner.
Along Y axes, from upper left corner.
Along X axes, from upper right corner.
Along Y axes, from upper right corner.
Along X axes, from lower left corner.
Along Y axes, from lower left corner.
Along X axes, from lower right corner.
Along Y axes, from lower right corner.
Fig. 4.41 Changing scan size.
By pressing the Feedback tab occurs feedback control panel opening. On it are
displayed sliders of feedback Integral, Differential and Proportional component and
Setpoint.
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Fig. 4.42 Feedback page.
4.13.1.
Signal description
Height
Sample surface topography.
DFL
Signal proportional to a probe deviation concerning a normal. Pays off as a difference
between signals from the top and bottom half of four-section photodiode. (Fig. 4.43).
DFL= (A+B)-(C+D).
LFL
Signal proportional to a probe deviation concerning a torsion. Pays off as a difference
between signals from the left and right half of four-section photodiode.
LFL= (B+D)-(A+C).
MAG
Magnitude of DFL signal…
MAG Sin
In-phase components of DFL signal
MAG Cos
Quadrature components of DFL signal
Phase
Phase of DFL signal.
MAG, MAG Sin, MAG Cos, Phase signals are computational result of ADC1 with phase-lock detector.
The direct digital synthesizer of frequency (DDS) which creates harmonious fluctuations with the set frequency
and amplitude lies at the heart of the phase-lock detector. This signal is deduced for a probe excitation and is
used for demodulation of the signals coming on the synchronous detector input.
ADC1 input signal arrives on a preamplifier (PGA) where can amplify in 1…100 times. The amplified signal ar rives on an input high-speed ADC. The digital signal from ADC output arrives on a multiplier input where it is
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multiplied with a basic signal, and also with the basic signal shifted on 90º. The received signals pass through
low frequencies filters, thus on an output signals MAG Sin and MAG Cos are formed. Amplitude (MAG) and the
Phase signals are calculated mathematically from these signals.
DInt
Total signal from all four sections of the photo diode. This signal is proportional to intensity
of the laser beam reflected from a cantilever.
Dint=A+B+C+D.
ADC 01
ADC01 signal, DFL
ADC 02
ADC02 signal, LF
ADC 03
ADC03 signal, DInt.
ADC 04
ADC04 signal.
ADC 05
ADC05 signal.
X sensor
The signal from capacity sensor by X scan head axes.
Y sensor
The signal from capacity sensor by Y scan head axes.
Z sensor
The signal from capacity sensor by Z scan head axes.
Ux
High voltage output for X axes head piezostack.
Uy
High voltage output for Y axes head piezostack.
Uz
High voltage output for Z axes head piezostack.
X2 sensor
The signal from capacity sensor by X scan stage axes.
Y2 sensor
The signal from capacity sensor by Y scan stage axes.
Z2 sensor
The signal from capacity sensor by Z scan stage axes.
Ux2
High voltage output for X axes stage piezostack.
Uy2
High voltage output for Y axes stage piezostack.
Uz2
High voltage output for Z axes stage piezostack.
ADC HR 1
Auxiliary analog input.
ADC HR 2
Auxiliary analog input.
Fig. 4.43 Foursection photodiode drawing.
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4.13.2.
Multi-pass technique
By pressing the button
the scanning two-through passage technique is activ-
ated. On the Scan tab there is a field LM height, nм for distance value on axis Z on
which the second pass of a probe will be carried out is established. Near to the fields of
a signals choice (Channel A, Channel B, Channel C, Channel D) appear buttons
Pressing such buttons
.
means the signal is chosen for obtaining on the second pass
of a probe.
Fig. 4.44 Scan tab in two-pass mode drawing.
4.13.3.
Additional scan parameters
The probe position is shown in the XY probe positioning panel, when the button
Point selection
has pressed.
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Fig. 4.45 Probe positioning panel drawing.
The Z Positioning slider is necessary for moving of a probe on axis Z. Position Z
can be set from the keyboard in the field near to the slider. After typing-in the number
value from the keyboard press the button Enter Key. Depending on a choice of a way of
scanning slider control or position on Z in a scanning head, or position on Z in a
scanning stage.
Fig. 4.46 Z positioning.
The Current Tip Position bar indicates Z scanner lever in percents. Green color
of the indicator corresponds to a safe supply of a probe, and red means that the probe is
too close to the sample and there is a possibility of probe damaging.
Fig. 4.47 Z position.
Fig. 4.48 Escaping high voltage amplifiers.
Set high voltages HYZ to zero – by pressing the button an output of
high-voltage amplifiers of the head scanner pressure is established to zero.
/
Fig. 4.49 Fast scanning button.
By pressing the Fast scanning button enables algorithm allowing to carry out fast
scanning by special algorithm.
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4.13.4.
Selection of scanning parameters
At set of scanning parameters choose values of following parameters:
• number of points;
• scan size area;
• signals for acquisition;
• signals for cut section displaying;
• scanning speed;
• If necessary to switch on a mode of program correction for fast scanning;
And after this start the scan process.
It is recommended to obtain overview scan, than to correct selection of feedback
parameters, probe oscillation parameters. We recommend following parameters for data
acquisition with maximum resolution:
• Full scan area;
• Points number 300х300 pixels;
• Scanning speed 1 line/sec (Hz);
• Signals Height and Phase for forward and backward directions.
After getting test images, you may select desired scan settings and the interesting
area on the surface.
To select the number of pixels in the image should be guided by the following
rules:
• For non-contact techniques does not make sense to put the number of
points, which is equal to resolution less than the probe curvature radius;
• Scanning speed depends on size of the scanning field for the same number
of points. It is recommended to reduce the number of points with decreasing scanning field to save the scanning speed in proportion to the size of
the scanning field or increase the scanning speed;
• For different sizes of the scanning field may need to change the parameters
of the feedback.
4.13.5.
Scanning conditions
At work with microscope Certus Standard without vibrating and acoustic protection it is recommended not to subject the device to vibrating and acoustic influences.
These influences can lead to occurrence of artifacts on the image and even to moving of
the sample concerning a microscope and probe damage.
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4.14. Scanning
For start scanning press the button Start
again this button
. For stop scanning press
. Scanning is started only after a choice of signals on the
Channel 1-4. For start enough one signal.
Fig. 4.50 Start scanning.
The check box for cut section construction for relevant channel. The title color is
relevant to the cut section color.
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Fig. 4.51 Start scanning with line cut section.
4.15. Primary image processing and saving
For primary results processing and saving use built-in tools to work with images
and graphics. A detailed description of the location and functions of these instruments is
given in the software NSpec user manual in sections:
Par. 2. Interface tools;
Par. 3. DATA window.
It is recommended to save data without filters processing and extra filters.
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4.16. Precise probe positioning
For precise positioning of a probe in the range of 100х100 micron with step 0.1
nanometers is used a scanning head. Positioning is applied for indentation, to obtain of
spectroscopy curves in SPM modes, and in aggregate with an optical microscope allows
to precisely position the probe for prompting on a site of a research object surface.
For precise probe positioning use the Point selection
/
button on the
3D panel. At pressing by the left mouse button in an active scan window the scanner
moves the probe to the chosen point.
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4.17. Scanner calibration
If a scanner have no calibration or a recalibration required, it is necessary to use
calibration tools. Scanner calibration contains a set of factors for recalculation of
voltage put to a piezostack in real displacement taking into account nonlinear effects
and factors for recalculation of capacity of sensors in displacement.
To implement the nonlinear correction, go to the option Oscilloscope
, click-
ing in the upper toolbar, the corresponding icon. In the right pane, find the section Scanner test /calibration (Fig. 4.52).
Fig. 4.52 Scanner calibrations tables.
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Close loop
The button of on/off switching of scanner close loop.
When close loop is on the button has blue color.
Non-linear correction
The button of on/off switching of scanner nonlinear correction. When close loop is on the button has green color.
PC File
Save calibrations in PC file.
PC File
Load calibrations from PC file.
DSP Memory
Save calibrations in DSP.
DSP Memory
Load calibrations from DSP (internal controller memory).
Show/hide calibration window
Show/hide calibration window
Firmware upgrade
Firmware upgrade from file function.
Speed [μm/s] of probe or stage moving in an start scan point or new position from
the previous position is in the field Free Positioning speed established.
The PID panel is designed to set PID control coefficients of capacity sensors
close loop. In fields Proportional, Integrated and Differential corresponding factors
for each axis are set (X, Y, Z).
On the panel Scanner Range in the field Range, μm scanning range for each axes
are set. The fields Scale gain and shift are designed to service adjustment of sensors.
On the Piezo calibrations panel for each axis (X, Y, Z) are set nonlinear calibration coefficients without sensors close loop. This panel contains the table of coefficients
of program piezostack nonlinear correction. This table coefficients is necessary for
non-linear conversion of the voltage U applied to piezostack to X movement. In the system EG-3000
4
3
2
U ( X )= A× X +B× X +C× X +D× X +E ,
U – voltage in DACs counts 0…65535, X – displacement in μm, 0… Xmax, this function
is working at NLC is ON
. If NLC button is off, voltage is calculates
by linear relationship
U ( X )=65535×
X
X max .
On the Senors calibrations panel for each axis (X, Y, Z) are set sensor calibration
coefficients for sensors close loop. This panel contains the table of coefficients of pro-
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gram sensor nonlinear correction. This table coefficients is necessary for non-linear conversion of the capacity C of the sensor to piezostack to X movement. In the system
EG-3000
4
3
2
C ( X )= A× X +B× X +C× X + D× X +E ,
С – sensor capacity in DACs counts 0…65535, X – displacement in μm, 0… Xmax. this
function is working at close loop is ON
. If close loop is off
, capacity is cal-
culates by linear relationship
С ( X )=65535×
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X max .
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4.18. Calibration procedure
4.18.1.
Calibration mode
For scanner calibration go to calibration mode by pressing Show/Hide calibration window
. Then in a window there will be tools for carrying out of calibra-
tions.
Fig. 4.57 Oscilloscope window in the calibration mode drawing.
4.18.2.
Piezostack calibration
• Switch off nonlinear correction and sensors close loop
;
• Scan test sample with the full amount of points (1000 x 1000) in the direction of
the calibration, and the full range, the direction of the fast scan X (measurements
should occur on the growth of the voltage from minimum to maximum)
;
• Produce a horizontal section of the image;
• Calculate calibration coefficients using Controls panel tools (Procedure of coefficients calculatiing is described below in point 4.17.5);
• Store new coefficients in the related table;
• Save data.
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4.18.3.
Sensors calibration
• Switch off nonlinear correction
and switch on sensors close loop
;
• Scan test sample with the full amount of points (1000 x 1000) in the direction of
the calibration, and the full range, the direction of the fast scan X (measurements
should occur on the growth of the voltage from minimum to maximum)
;
• Produce a horizontal section of the image;
• Calculate calibration coefficients using Controls panel tools (Procedure of coefficients calculatiing is described below in point 4.17.5);
• Store new coefficients in the related table;
• Save data.
4.18.4.
Tool panel Settings
Fig. 4.58 Controls panel.
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Acquire data
Get data from the selected source.
Filters
Standard filters for curves.
Save to settings
Store obtained coefficients in the related table.
Sensors autoadjustment
Run sensors automatic adjustment.
Tools panel Settings:
Output
Combo box for device for calibration choise: head or stage
Channel
Combo box for calibration channel choice
Voltage Ux
X piezostack calibration
Voltage Uy
Y piezostack calibration
Voltage Uz
Z piezostack calibration
Sensor Cx
X sensor calibration
Sensor Cy
Y sensor calibration
Sensor Cz
Z sensor calibration
Scan section
For calibration the profile is used directly from the scanned
image
Section from 3D data
For calibration the profile is used from the earlier saved
one
Section from Data
Use for calibration the section stored in the file.
Source
Falling edge
Installations of points of a binding on the falling edge of
test structures:
Level, 0…1
Point level,
Period, μm
Test structure period.
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4.18.5.
Calibration coefficients obtaining
Let's consider the example. For piezostack calibration of a scanning head on an
axis X by the image saved in a file earlier it is necessary to go to the Data unit, to open
earlier scanned image of a test grating and to construct its section. For constructing the
section set up marker on the scan by the button Marker
Section
and the button Markers Horizontal mode
, press the button Cross
.
Fig. 4.59 Profile for calibration.
Then go to Oscilloscope unit, press Show/Hide calibration window
,
select Head in the Device combo box, select Voltage Ux in the Channel combo box,
select 3D data Section in the Source, and type-in the gratings period. And then press
the button Acquire data
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Fig. 4.60 Calibration curve.
Apply filters for section nonlinear correction
.
Fig. 4.61 Calibration curve after filter applying.
Markers on the curve can be moved manually in case of wrong automatic installation.
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Fig. 4.62 Calibration curve.
After loading calibration structure curve and carrying out all steps for calculation
of polynomial coefficients, in the frame Coefficients it will be shown.
Fig. 4.63 Polynomial coefficient.
Then press the button Save to settings
, to store polynomial coefficients on
the chosen axis in the Piezo Calibration table.
Similarly coefficients are defined for other axes and scanners, and for capacitor
gauges. After getting all coefficients it is necessary to keep options by pressing the button PC File
.
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5. SPM Certus head application with external optical equipment
5.1.
Basic principles of optical equipment application
Scanning probe microscope Certus Standard is designed for use with optical
equipment. The SPM head Certus design can combine it with both direct and inverted
microscope, to inject additional sources of light, such as lasers, to use regular microscopes light sources, etc.
One of the basic restrictions of a scanning probe microscope is difficulty in search
of an interest site on a research object surface, and as probe positioning in the chosen
point on a surface. To bypass this restriction use of techniques of optical microscopy
and spectroscopy allows.
The full range of positions of lenses concerning an axis passing through a tip
makes 0-90 ° for a direct microscope and 0 ° for the inverted. The maximum diameter
of used lenses in case of a direct microscope-40 mm, and for inverted lenses diameter is
limited only by their design.
The working distance of lenses (WD) is 12 mm for direct microscope, and for the
inverted microscopes is limited only by thickness of a used substrate.
For combination of techniques optical and scanning probe microscopy the field of
vision of an optical microscope is necessary to combine with scanning area of a scanning probe microscope.
Fig. 5.1. External objective application.
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5.2.
Example
The combination of the upright optical microscope allows to study both transparent and opaque objects. In this case, you should align microscope field of view and tip
position (Fig. 5.2). Furthermore, using optical microscopy techniques and sample
movers you can to select interesting areas on the research surface and scan it.
Fig. 5.2 Sample and cantilever tip image.
5.3.
Video-videocam mode adjustment
In the SPM Certus Standard built-in optical microscope with CCD sensor. The
Video unit is used to work with and adjustment of camera.
Fig. 5.3 Video unit drawing.
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5.4.
Video unit basic functions
To entry Video window press
, that is situated on the top panel of the
NSpec window.
Start/stop
Start/stop CCD camera video imaging.
Automatic white balance
Enables automatic white balance adjustment. Repeated pressing of
the button disables this.
Automatic exposure
Enables automatic exposure adjustment. Repeated pressing of the
button disables this.
Autoadjustment
Enables automatic white balance and exposure adjustment. Repeated pressing of the button disables this.
Autofocus by image
Enables automatic focusing by image. Lens Z position is controlled
by the slider Obj. Z.
Autofocus by laser spot
Automatic focusing by reflected laser. Enable with only Centaur
device.
Save image
Saving current CCD image in the raster format file.
Start recording
Recording CCD video in *. avi file.
Show tip scan area
The scan areas by tip and by stage are shown on the video image. It
corresponds to piezoscanner and may has various range.
Show laser scan area
The scan areas by stage are shown on the video image related to
laser spot. (not available in Certus Standard)
Settings
Lenses settings.
Measure distance
Distance measurement by video image. It makes sense when only
the lens has a calibration.
Show axes
Enables axes on the video image. It makes sense when only the
lens has a calibration.
Show grid
Enables grin on the video image.
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Fig. 5.4 Scan area demonstration
Fig. 5.5 Measuring tool
.
.
Each scan area has its own color. Scan area by head has the blue.
Fig. 5.6 Scan areas colors.
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To disable the axes press the button
.
Fig. 5.7 Video without axes.
To disable the grid press the button
.
Fig. 5.8 Video without axes and grid.
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5.5.
Lenses calibration
Work with devices and complexes form company «Nano Scan Technology»
means possibility to use various lenses of various manufacturers. As lenses have various
characteristics, such as the zoom, focal length and work distance, it is necessary to
spend adjustment for each used lens. Lens adjustment includes calibration on the test
sample and combination of scanning fields of SPM with the optical image.
5.5.1. Settings panel main functions
For lens adjustment or configuration changing press the button Settings
.
The panel of options will be displayed.
Fig. 5.9 Video with lens settings panel.
Add new configuration
Creates new lens configuration
Remove current configura- Remove current lens configuration
tion
Measure reference
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Tool for measuring reference length. The reference length is entering in the Line length field.
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Tip scan area center align- The scan areas by tip and by stage are shown on the video image.
ment.
By mouse clicking scan area center moves to mouse point.
Laser scan area center The scan areas by stage are shown on the video image related to
alignment (not available in laser spot. By mouse clicking scan area center moves to mouse
Certus Standard)
point.
5.5.2. Tools panel Settings
Fig.5.10 Tool panel
Combo box with available configurations.
The list of available configurations is enumerate in the combo box.
Name:
Current configuration name. Name of new configuration is entered
here.
Range X:
X axes field of view size
Range Y:
Y axes field of view size
Width
Width of the image in percentage of width of a matrix
Height
Height of the image in percentage of height of a matrix
Line length
The field to enter the reference size of the test structure.
Flip X.
Horizontal image flip.
Flip Y.
Vertical image flip.
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5.5.3. New lens calibration
For new lens calibration it is necessary to focus on the test sample surface and
produce following steps:
• Press the button Add new configuration
;
• Enter the configuration name;
• Enter reference size of the test structure;
• Using tool Measure reference
select reference structure on the video im-
age. Irrespective of a numerical ruler length on the image its length will make a
preset value and all axes will be calibrated according to set the reference. See figure 5.11.
Fig. 5.11 Creating new lens configuration.
After input of the reference size and its choice on the image there will be a
change of axes scale of the image according to the reference size.
5.5.4. Scan field selecting
After lens calibration and creation of a new profile it is possible to spend combination and/or installation of fields of scanning. For this purpose it is necessary to press
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the button Tip scan area center alignment
and having clicked on object on the
video image to define a scanning field center. The sizes of scan fields are set according
to the sizes stored in the file of options.
Fig. 5.13 Scan fields select.
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5.6.
Microscope positioning
For microscope focusing and positioning use the focusing and positioning knobs.
A
Microscope focusing knob
B
Microscope mover knob
C
Microscope mover knob
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