Lecture-4
I Scanning Electron Microscopy
• What is SEM & Working principles of SEM
• Major components and their functions
• Electron beam - specimen interactions
• Interaction volume and escape volume
• Magnification, resolution, depth of field and
•
•
•
•
image contrast
Energy Dispersive X-ray Spectroscopy (EDS)
Wavelength Dispersive X-ray Spectroscopy
(WDS)
Orientation Imaging Microscopy (OIM)
X-ray Fluorescence (XRF)
II Scanning Probe Microscopy (SPM)
http://www.youtube.com/watch?v=sFSFpXdAiAM
http://www.youtube.com/watch?v=tDzInhT5zzQ
at~0.55-1:35
Resolution of Images
The resolution is the pixel diameter on specimen surface.
The optimum condition for imaging is when the escape
volume of the signal concerned equals to the pixel size.
Effect of probe size on
escape volume of SE
e10nm
BSE
X-ray
P=D/Mag = 100um/Mag
1m
5m
http://www.youtube.com/watch?v=K7G3U7rn5uU
~0:30 What is X-ray spectroscopy
X-ray Spectroscopy -Chemical Analysis in SEM
• X-rays are produced when energetic
electrons strike a solid sample
• By measuring and analyzing the energy
and intensity distribution of the X-ray
photons
E (eV) = hc/l (nm) h=4.136x10-15 eV sec
elemental concentration or composition of
the sample can be determined
There are two ways to measure the energy
distribution of X-rays emitted from sample:
• Energy dispersive spectroscopy (EDS)
• Wavelength dispersive spectroscopy (WDS)
How are X-rays produced?
http://www.youtube.com/watch?v=IRBKN4h7u80
~0:30
http://www.matter.org.uk/tem/electron_atom_interaction/introduction.htm
Principles of X-ray Production
(20keV)
1. Ionization-excitation
L
K
Create a vacancy
in K shell
excited state
E-E
2. Relaxation-deexicitation
E
K
L
e- in L shell jumps
in to fill vacancy
K
Auger Electron
Emission
radiative
X-ray are
produced
by transitions
of electrons
between shells
of atoms
Shells
correspond to
particular
energy level
for an atom
Transition
between shells
and energy
levels are
characteristic
of element
L
nonradiative
Process of inner-shell ionization and subsequent deexcitation
http://www.matter.org.uk/tem/electron_atom_interaction/x-ray_and_auger.htm
Excitation of K, L, M and N shells and
Formation of K to M Characteristic X-rays
 If an incoming electron has
sufficient kinetic energy for
knocking out an electron of the
K shell (the inner-most shell),
it may excite the atom to an
high-energy state (K state).
M
K
EK>EL>EM
EK>EK
4/9/2015
K2
K1
K
 One of the outer electron falls
into the K-shell vacancy,
Energy
emitting the excess energy as
a x-ray photon.
 Characteristic x-ray energy:
Ex-ray=Efinal-Einitial
L
K excitation
K
L
M
N
I
II
III
L
subshells
K state
(shell)
K
K
L state
L
M state
L excitation
M
N state
ground state
K emission spectrum of copper
K
I
K
K
K
Energy (eV)
EDS - Basics
E (eV) = hc/l (nm)
• In most of the modern EDS
Si (Li) detector
system, a semiconductor
detector is used for
measuring the energy of
the x-ray photon emitted
from the specimen. The XLN2
ray energy is displayed as
Be window
a histogram of number
of photons versus
specimen
energy.
• Liquid nitrogen is for
cooling the detector so as
Owing to the use of Be window, only
to reduce noise caused by elements higher than Be can be detected.
thermal excitation.
• A window is therefore
I
required for protecting the
detector against
condensation when the
sample chamber is
opened.
http://www.youtube.com/watch?v=gd-mzdIHnOc
Kev
Applications of EDS: I. Microchemical Analysis




BaL1
BaL2
BaL1
CuK

YK
Characteristic X-ray Spectrum of YBaCuO6.9 Superconductor
• As Z increases the Kth shell line energy increases (Y vs Cu).
• If K-shell is excited,then all shells are excited (Y, Cu, Ba)
but they may not be detected.
• Severe spectral overlap may occur for low energy lines.
Quantitative Analysis – Thin Samples
Cliff-Lorimer Technique
Ca
Cb
= Kab
IA
IB
NiSn alloy
Ca and Cb are weight fraction of element a and b
IA and IB are the peak intensities
Kab is a constant depending on the two elements
and the operating conditions, and can be obtained
by using a standard sample.
Applications of EDS: II. X-ray line scan
This powerful 3D EDS solution
combines EDS analysis
software syncronised to the
milling capabilities of a FIB
(Focused Ion Beam)-SEM. FIB
milling is followed by EDS X-ray
map acquisition for each slice
http://www.oxford-instruments.com/products/microanalysis/energydispersive-x-ray-systems-eds-edx/eds-for-sem/3d-eds-analysis
Applications of EDS: III. X-ray Mapping
Carbon
Silicon
Calcium
Overlaying
EDS map of a sandstone
showing the distribution of carbon, silicon and calcium
http://www.youtube.com/watch?v=wcHSg-uCXOg
WDS - Basics
Wavelength Dispersive Spectroscopy
E (eV) = hc/l (nm)
Bragg’s Law: 2d sin = l
• A crystal of fixed
d is moved along
a circle to vary 
so that x-ray of
different l is
recorded.
• No window
needed, therefore
light elements can
be detected
• Peak very sharp
• Very large S/N
ratio c.f. EDS.
1
1 ~ l 1
2 ~ l 2
2
I
l
X-ray is diffracted by LiF crystal and detected by a
l
proportional counter, and then amplified, processed.
X-ray intensity is displayed as a function of l.
~3:35
EDS vs WDS
WDS
EDS
Spectra
Acceptance
one element
per run
entire spectrum
in one shot
Collection time
tens of min
mins
Resolution
~a few eV
~130eV
Probe size
~200nm
~5nm
Max. Count rate
~50000 cps
<2000 cps
Detection limits
100ppm
Accuracy
~4-5wt%
Spectral artifacts
rare
1000ppm
~4-5wt%
peak overlap
absorption
etc.
cps - count/second on an X-ray line
EDS vs WDS
EDS
FWHM=135-eV
WDS
FWHM=a few-eV
Wavelength (nm)
Superposed EDS and WDS spectra from BaTiO3. The EDS
spectrum shows the strongly overlapped Ba L-Ti K and
Ba L1-Ti K peaks. The WDS peaks are clearly resolved.
Orientation Imaging Microscopy (OIM)
OIM is based on electron backscatter diffraction
Electron backscatter diffraction
Phosphor
patterns (EBSP) are obtained in
screen
SEM by focusing e beam on a
crystalline sample.
Diffraction pattern is imaged on
a phosphor screen and captured
using a CCD camera.
e70o
specimen
OIM is based on an automatic
indexing of EBSP and provides a
complete description of the
crystallographic orientations in
polycrystalline materials.
Effects of the crystal orientations on materials properties.
EBSP
http://www.stanford.edu/group/snl/SEM/OIMIntro.htm
http://www.youtube.com/watch?v=dSbyPYmBrUk
at~1:40-5:08
Information provided by EBSP
The bands in the pattern are referred to as Kikuchi bands
are directly related to the crystal lattice structure in
sampled region. As such, analyzing the pattern and bands
provide key information about the crystal structure for
measured phase:
and
the
can
the
•The symmetry of the crystal lattice is reflected in the pattern.
•The width and intensity of the bands are directly related to the
spacing of the atoms in the crystal planes.
•The angles between the bands are directly related to the angles
between planes in the crystal lattice.
Fast and Accurate Indexing of Any
Crystal System
Cubic
Tetragonal
Hexagonal
Triclinic
Monoclinic Orthorhombic
Trigonal
Applications of OIM
•Orientation/misorientation
Physical properties are often orientation dependent
Young’s modulus, permeability, hardness, plasticity, etc.
Fatigue mechanism, creep in superalloys, integrity of
single crystals, in-service reliability of microelectronic,
corrosion, cracking, fracture, segregation and
precipitation, twinning and recrystallization, etc.
•Phase identification-coupled with chemical analysis
Distinguish between phases having similar chemistries
Distinguish between body-centered cubic and face
centered cubic form, etc.
•Strain
Strain in superalloys and aluminum alloys
Assessment of implantation damage in Si from Ge ions
http://www.youtube.com/watch?v=dSbyPYmBrUk
at~6:58-9:18
OIM-Grain Boundary Maps
Grain Boundary Map
Orientation Map
A Grain boundary Map can be generated by comparing the orientation
between each pair of neighboring points in an OIM scan. A line is
drawn separating a pair of points if the difference in orientation
between the points exceeds a given tolerance angle. An Orientation
Map is generated by shading each point in the OIM scan according to
some parameter reflecting the orientation at each point. Both of these
maps are shown overlaid on the digital micrograph from the SEM.
OIM-Semiconductors
Effect of microtexture on Mean
Time to Failure
(MTF) of interconnect lines and
thin films for
semiconductor
applications.
Good film
Bad film
SEM Specimen Preparation
• Remove all water, solvents, or other materials
that could vaporize while in the vacuum.
• Flat surface is required for BSE and OIM
• Firmly mount all the samples.
• Non-metallic samples, such as building
materials, insulating ceramics, should be
coated with a thin conductive layer to eliminate
image artifacts which arise from excess surface
charge. Metallic and conducting samples can
be placed directly into the SEM.
Line by line charging
http://www.youtube.com/watch?v=SaaVaILUObg
at~2:33-3:00
Coating Techniques
Sputter coater is used to coat insulating samples
Au and Al – good for SE yield
AuPd alloy – good for high resolution
C – used if X-ray microanalysis is required
Coating should have low granularity in order not to
mask the underlying structure (<20nm thick).
http://www.youtube.com/watch?v=NlVCJG3bEwo
X-ray Fluorescence (XRF)
XRF is the emission of characteristic "secondary" (or fluorescent)
X-rays from a material that has been excited by bombarding with
high-energy X-rays. The phenomenon is widely used for
elemental analysis and chemical analysis, particularly in the
investigation of metals, ceramics and building materials, and for
research in geochemistry, forensic science and archaeology.
Main use
Samples
Range of elements
Accuracy
Detection limits
Depth sampled
Instrument cost
Identification of elements; determination of composition and thickness
(for thin film samples)
Solids, powders and liquids; 5.0cm
in diameter
All but low-Z elements: H, He, and Li
1% composition, 3% thickness
0.1% in concentration
Normally in the 10nm range, but can
be a few nm in the Total-reflection XRF
$400K-$2.4M
http://en.wikipedia.org/wiki/X-ray_fluorescence
http://www.amptek.com/pdf/xrf.pdf
X-ray Microfluorescence (XRMF) - Basics
http://www.youtube.com/watch?v=-unHRyx0gOE
at~2:20-3:06
XRMF Spectrometer-Eagle II
1.
2.
3.
X-ray irradiates specimen
Specimen emits characteristic X-rays or XRF
Detector measures position and intensity of XRF peaks
http://www.edax-marcomportal.com/largedownload/orbismodel/index.html
XRMF Analysis - line scan
A fast, convenient
way
to
examine
sample
chemistry
and heterogeneity
along a line of
analysis points.
Ideal for studying
diffusion profiles or
layered materials.
Line scan done on a printed circuit board
Elemental Mapping
Qualitative
Quantitative
Spatial distribution
Cu
map
Pb
map
Scanning Probe Microscopy (SPM)
•
•
•
•
•
•
•
What is SPM?
Working principles of SPM
Basic components and their functions
Scanning Tunneling Microscopy (STM)
Atomic force microscopy (AFM)
Advanced SPM techniques
Examples of SPM images
FESEM: “Seeing” materials at the nanoscale
SPM: “feeling” materials at the nanoscale
http://www.youtube.com/watch?v=WiFgwB_BADE
http://www.youtube.com/watch?v=oOmxg4u9efs
A journey to the nanoworld
Advanced SPM Lecture
http://www.youtube.com/watch?v=zW4x0grQT2U
Rohrer
History of STM
Binning
Invented at IBM by
Gerd Binning and
Heinrich Rohrer
Nobel Prize in 1986
STM
2nm
STM of silicon-Si(111)
7x7reconstruction
http://www.youtube.com/watch?v=y18WGOWmLuQ&feature=related
http://en.wikipedia.org/wiki/Scanning_probe_microscope
Typical STM and AFM
Modules
Dimension 3100 AFM
The world's best selling SPM
T: 4K – 300K
UHV <5x10-11mbar
Low temperature STM
atomic resolution at 5K
The world's first truly flexible
SPM, providing a single system
that could meet all of the the
needs of most scientists and
engineers at an affordable price.
Cost: $500K(ambient) to $1.6M (ultrahigh vacuum)
Basic Principles of SPM (STM & AFM)
SPM relies on a very sharp probe positioned within a few
nanometers above the surface of interest. When the probe
translates laterally (scanning) relative to the sample, any
change in the height of the surface causes the detected
probe signal to change.
A 3-D map of surface height is carried out with a probe
scanning over the surface while monitoring some interaction
between the probe and the surface.
Probe signals that have been used to sense surfaces include
electron tunneling current (STM), interatomic forces
(van der Waals force, AFM), magnetic force (MFM),
capacitive coupling (SCM), electrostatic force (EFM), and
thermal coupling (SThM), etc.
The probe signals depend so strongly on the probe-sample
interaction that changes in substrate height of ~0.1Å can be
detected with a sub-nm lateral resolution.
http://www.youtube.com/watch?v=Ha53tFTsmW8
at~0:30
How Does SPM Work?
The SPM creates images with the
sense of touch instead of light or
electrons. Imagine drawing a
picture of a computer keyboard
without using your eyes. You could
drag your fingertip over the
surface to "feel" what the
keyboard looks like. Instead of a
fingertip, the SPM has a very tiny
sensor called a probe. The SPM
can magnify an object up to
10,000,000 times. In the
laboratory under ideal conditions,
the SPM can be used to look at
individual atoms.
http://www.youtube.com/watch?v=MZb8C0f7Kdg
http://www.doitpoms.ac.uk/tlplib/afm/intro.php
Piezoelectric
Scanner
Piezoelectric
Scanner
http://www.youtube.com/watch?v=Ha53tFTsmW8
Basic SPM Components
•Scanning System: Scanner - the heart of the microscope.
It may scan the sample or the probe. A piezoelectric tube
scanner can provide sub-Å motion increments.
•Probe (tip): Very sharp tips are secured on
the end of cantilevers which have a wide
range of properties designed for a variety
of scanning probe technologies. There are
also many types of tips with varying shapes
for probing different morphologies and
scales of surface features and materials
(conducting, magnetized, very hard, etc.).
•Probe Motion Sensor: Senses the
spacing between the probe and the
sample and provides a correction
signal to the piezoelectric scanner
to keep the spacing constant. The
common design for this function is
called beam deflection system as
shown at right figure.
http://www.doitpoms.ac.uk/tlplib/afm/cantilever.php
http://www.doitpoms.ac.uk/tlplib/afm/feedback_circuit.php
Actuators - Piezoelectric Scanner
in Scanning Probe Microscopy (SPM)
Scanning Tunneling Microscopy (STM) STM uses a piezoelectric scanner to
scan an electrical probe over a surface
to be imaged to detect a weak electric
current flowing between the tip and
the surface.
A piezoelectric tube scanner can
provide sub-Å motion increments
Piezoelectric scanner
(PZT)
to ~0.:55
http://www.youtube.com/watch?v=lIszD5CneQQ&feature=related
Piezoelectric materials convert mechanical to
electrical energy (and vice versa).
PZT - Pb(ZrTi)O3
3
Direct
D = d
1
2
Converse
S = dE
D-Charge density or dielectric displacement (C/m2), -stress (N/m2),
S-strain, E-electric field and d-piezoelectric constant (C/N or m/V)
D3(P3)=d333
S3=d33E3
http://www.doitpoms.ac.uk/tlplib/piezoelectrics/polarisation.php
http://www.youtube.com/watch?v=Xuw9frP1GNo&feature=related
Electrode
Piezoelectric Material, such as Pb(ZrTi)O3 or PZT
A piezoelectric tube scanner can provide sub-Å motion increments
How does a piezoelectric
scanner work?
http://www.chembio.uoguelph.ca/educmat/chm729/STMpage/stmtutor.htm
Scanning Tunneling Microscope(STM)
It=Ve-Cd
tip
V
vacuum
d~10Å
90%It
STM uses a sharpened,
conducting tip with a bias
voltage applied between
the tip and the sample.
When the tip is brought
within about 10Å of the
sample, electrons from the
sample begin to "tunnel"
through the 10Å gap into
the tip or vice versa,
depending upon the sign of
the bias voltage.
sample
It varies with tip-to-sample spacing and is also a function of
local electronic structure or surface state. It is the signal
used to create a STM image. For tunneling to take place, both
the sample and the tip must be conductors or
semiconductors. http://www.youtube.com/watch?v=y18WGOWmLuQ&feature=related
Two Scanning Modes in STM
Imaging of surface topology can be done in one of two ways:
Scan direction
Tunneling current is monitored as
the tip is scanned parallel to the
surface.
There
is
a
periodic
variation in the separation distance
between the tip and surface atoms.
A plot of the tunneling current v's
It
It
tip position shows a periodic
variation which matches that of the
surface structure-a direct "image"
constant height mode of the surface.
Scan direction
Tunneling current is maintained
constant as the tip is scanned
across
the
surface.
This
is
achieved by adjusting the tip's
height above the surface so that
It
It
the tunneling current does not
vary with the lateral tip position.
The image is then formed by
plotting the tip height v's the
constant current mode
lateral tip position.
http://www.doitpoms.ac.uk/tlplib/afm/feedback_circuit.php
http://www.doitpoms.ac.uk/tlplib/afm/tip_surface_interaction.php
Atomic Force Microscope (AFM)
AFM senses interatomic forces that occur between a probe
tip and a sample.
Photo diode
detector
Probe tip
Modules
Piezoelectric sample
scanner
a laser beam bounces
off the back of the
cantilever onto a
photodiode. As the
cantilever scans over a
sample it bends and the
position of the laser
beam on the detector
shifts. The cantilever
deflection is regarded
as the vertical force
signal between the tip
and the sample surface.
The local height of the
sample is measured by
recording the vertical
motion of the tip
Optical lever detection of cantilever deflection while keeping the
3-D topographical maps of the surface are then cantilever deflection at
constant.
constructed by plotting the local sample height
versus horizontal probe tip.
http://www.youtube.com/watch?v=Ha53tFTsmW8
http://www.youtube.com/watch?v=veTskO7EWM8&feature=related
Silicon Nitride-Contact Mode AFM Probe
Substrate
Tip
Cantilever
Probes
Spring constants
(N/m)
cantilever
The properties and
dimensions of the
cantilever play an
important role in
determining the
sensitivity and
resolution of the
AFM.
http://www.youtube.com/watch?v=veTskO7EWM8&feature=related
http://www.youtube.com/watch?v=oyS15QZyfkI&feature=relmfu
Contact
Non-contact
Contact, Non-Contact and TappingMode AFM
Contact
a
Non-contact
b
Tapping
c
Measure topography by
a.Sliding the probe
tip across surface
b.Sensing Van der Waals
attractive forces between
surface and probe tip
held above surface
c.Tapping the surface
with an oscillating probe
tip
Contact mode imaging is heavily influenced by frictional and
adhesive forces which can damage samples and distort image
data. Non-contact imaging generally provides low resolution and
can also be hampered by the contaminant layer which can
interfere with oscillation. TappingMode imaging eliminates
frictional forces by intermittently contacting the surface and
oscillating with sufficient amplitude to prevent the tip from
being trapped by adhesive meniscus forces from the
contaminant layer. The graphs under the images represent likely
image data resulting from the three techniques.
http://www.doitpoms.ac.uk/tlplib/afm/modes_operation.php
LiftMode AFM
2nd pass
1st pass
Magnetic or electric
Field source
Lift height
Topographic image
Non-contact
Force image
LiftMode is a two-pass technique for measurement of magnetic
and electric forces above sample surfaces. On the first pass over
each scan, the sample's surface topography is measured and
recorded. On the second pass, the tip is lifted a user-selected
distance above the recorded surface topography and the force
measurement is made.
Topographic structure (a) and Magnetic
force image (b) of a compact disk
a
b
Topographic structure results from surface preparation and
exhibits striations from a polishing process (imaged using
Tapping Mode) and magnetic force image (LiftMode and lift
height 35nm) shows small magnetic domains that are
unrelated to surface topography.
Image Insulating Surfaces at High
Resolution in Fluid - AFM
18nm
1
Fluid cell for an AFM which allows
imaging in an enclosed, liquid
environment.
2
Image of two GroES
(protein) molecules
positioned side-by-side in
fluid, demonstrating 1nm
lateral resolution and
0.1nm vertical resolution.
Entire molecule measures
84Å across and a distinct
45Å “crown” structure
protrudes 8Å above
remaining GroES surface.
Advanced SPM Techniques
• Lateral Force Microscopy (LFM)
measures frictional forces between the probe tip
and the sample surface
• Magnetic Force Microscopy (MFM)
measures magnetic gradient and distribution
above the sample surface; best performed using
LiftMode to track topography
• Electric Force Microscopy (EFM)
measures electric field gradient and distribution
above the sample surface; best performed using
LiftMode to track topography
• Scanning Thermal Microscopy (SThM)
measures temperature distribution on the sample
surface http://www.youtube.com/watch?v=zSvm1KaEd6k&feature=related
Advanced SPM Techniques
• Scanning Capacitance Microscopy (SCM)
measures carrier (dopant) concentration profiles
on semiconductor surfaces
• Nanoindenting/Scratching
measures mechanical properties of thin films and
uses indentation to investigate hardness, and
scratch or wear testing to investigate film adhesion
and durability
• Phase Imaging
measures
variations
in
surface
properties
(stiffness, adhesion, etc.) as the phase lag of the
cantilever oscillation relative to the piezo drive and
provides
nanometer-scale
information
about
surface structure often not revealed by other SPM
techniques
• Lithography
Use of probe tip to write patterns
Applications of SPM
To resolve a wide range of surface properties on the
nanometer scale including:
Topography, mechanical, magnetic, electric, thermal,
and etc.
e.g., Nano lithography, inspecting defects of
semiconductors, measuring physical and chemical
properties of surface, DNA imaging, etc.
Advantages:
Superior resolution and versatility of scanning probes
Limitations:
Long imaging times due to slow scanning speed
The maximum imaging area is limited (<mm2)
Examples of AFM Images
3-D
Al2O3
10m
80nm tall elevated features in
a Si/Si3N4 substrate
4m
Grain growth studies
Lateral force map of a patterned,
monolayer, organic film
deposited on a gold substrate.
The strong contrast comes from
the different frictional
characteristics of the two
materials. 30 µm scan.
Electric Force Microscopy (EFM) Mode :
Ferroelectric Domains on BaTiO3 Surface
-
+
- Ferroelectric domain
1 m
Piezoresponse force microscopy of ferroelectric domains on BaTiO3
surface. 5µm Scan courtesy of S. Kalinin, T. Alvarez, D. Bonnell,
Department of Material Science Engineering, University of
Pennsylvania.
Nanoindentation
metal-foil
diamond tip
200nm
Indentation depths are deeper for the
softer thin film (right).
Using a diamond tip to
indent a surface and
immediately image the
indentation. Using
indentation cantilevers,
it is possible to indent
various samples with the
same force in order to
compare hardness
properties.
Indentations on two
different diamond-like
carbon films using
three different forces
(23, 34, and 45N)
with four incidents
made at each force to
compare difference in
hardness.
IC Failure Analysis and Defect Inspection
with Scanning Thermal Microscopy
a
b
a. Top-view image of surface topography of a failing IC where
emission microscope detected two current leakage points but
did not give the exact location of failure. The image shows no
topographical features which suggest a problem. b. Scanning
thermal microscopy (SThM) temperature distribution map of
the same area showing a hot area on the surface above what
was found to be a gate oxide short.
Nanolithography
STM - Seeing Atoms
STM image showing single-atom
defect in iodine adsorbate lattice
on platinum. 2.5nm scan
Iron on copper (111)
http://www.youtube.com/watch?v=YcqvJI8J6Lc&feature=related
http://www.youtube.com/watch?v=BUq2bQkL1zo
Factors Influencing the Resolution of SPM
•
•
•
•
Broadening
Aspect ratio
Compression
Interaction forces
Tip broadening arises when
the radius of curvature of
the tip is comparable
with, or greater than, the
size of the feature trying to
be imaged.
Tip
The aspect ratio (or cone angle)
of a particular tip is crucial when
imaging steep sloped features.
http://www.doitpoms.ac.uk/tlplib/afm/tip_related.php
Image
Surface
AFM Images Acquired with Two Different Tips
a
b
Contact AFM images of the same area of a (001) oriented TiO2
thin film, acquired with a pyramidal Si3N4 tip (a) and a conical,
etched Si tip (b). Both images are on the same scale and in the
same surface orientation. Clearly, the surface morphology
appears different in each image and is convoluted with the
tip shape.
Do review problems for SEM and SPM
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X-ray Diffractiona
b