NanoSIMS 50/ 50L
Secondary Ion Mass Spectrometer
for trace element and isotope analysis
at sub-micron resolution
INTRODUCTION TO THE INSTRUMENTATION
NanoSIMS 50
Key components
Duoplasmatron source: OWien mass filter for the duo
NEG
Optical
microscope
Normal Electron
flood Gun (option)
X-Y sample
stage motors
Retractable Cesium source: Cs+
Magnetic sector mass analyzer
Multi-collection:
5 EM plus 1-2 FC (NS50),
7 EM-FC (NS50L)
Fixed
Large Detector
(NS50 LD option)
Ion pump
for intermediate
chamber
Ion pump + Ti sublimator
for Analysis chamber
Co-axial primary and secondary ion beams
Parallel detection of five (NS50) or seven (NS50L) ionic species
High transmission at High Mass Resolution
UHV technology, dry primary pump, turbomolecular pumps, ion
pumps and titanium getter
NanoSIMS 50
Sample introduction
Vacuum controller
Transfer Rod
Intermediate/ Analysis
Intermediate/ Analysis
Isolation Valve
Intermediate
chamber
Transfer Rod
Load-lock/ Intermediate
Load-lock
Heating lamp, turbo-pump
Load-lock/ Intermediate
Isolation Valve
Selection of sample
holder on Carrousel
(8 parking positions)
Standard 2-inch load-lock with turbo pumping, heating lamp for
sample degasing, mechanical transfer rod to the storage chamber.
8-position intermediate storage chamber with ion pumping,
transfer rod to the analysis chamber.
Vacuum automation with independant processor
NanoSIMS 50
Ultra fine feature
SIMS analysis requirements
1) FUNDAMENTAL LIMITATION: SIMS sensitivity gets poorer as lateral
resolution gets better (SIMS is destructive)
There are typically 1.25M atoms in a volume of 50 x 50 nm x 10 nm. With an ionisation of 0.005
and a transmission of 1, one can detect around 6000 atomic ions, meaning a detection limit of
roughly 0.1at. % level from a single pixel volume.
For comparaison, using a CAMECA IMS instrument with larger beam current over a larger area
(50 x 50 µm x 10 nm), one will sputter 1.25E12 atoms and be able to reach ppb level from the
whole area. This illustrates the compromise between lateral resolution and sensitivity,
exacerbated in a destructive technique (one can not only accumulate longer, as sample is
sputtered away).
2) HIGH LATERAL RESOLUTION together with HIGH BEAM DENSITY:
==> short working distance, normal incidence, high brightness ion sources
3) HIGH IONIZATION YIELD OF SPUTTERED PARTICLES (small and
limited volumes available, SIMS is destructive):
The use of reactive primary ions (Oxygen and Cesium) is mandatory in order to enhance atomic
secondary ions, in dynamic SIMS mode (sputtering of at least a few nm for trace element
analysis). Gallium gives 100-1000x less elemental signal in general.
No LMIS Gold or Bismuth as used on TOF-SIMS: enhancing molecular ion yield for static SIMS
mode is of no use for element or isotope analysis in dynamic SIMS.
4) HIGH TRANSMISSION MASS SPECTROMETER and PARALLEL
DETECTION
Small volumes available + perfect image or isotope registration ==> TOF or MAG. No
quadrupole (low transmission and monocollection).
High transmission together with high lateral resolution ==> Microprobe mode (ion microscope
mode not usable for sub-micron resolution: low transmission)
5) HIGH MASS RESOLUTION together with SMALL SPOT:
==> MAGNETIC SECTOR (no TOF analyzer: small spot OR high mass resolution , no
quadrupole analyzer: Low Mass Resolution)
6)
REASONABLE ACQUISITION TIME:
==> MAGNETIC SECTOR
(no TOF: much too low duty
200-1000 longer acquisition time for same element or isotope signal)
NanoSIMS 50
cycle
&
data
rate:
NanoSIMS 50 synopsis
Two reactive ion sources:
O-, Cs+
Normal, co-axial
primaries &
secondaries
Parallel detection
of five ionic species
(NS50) or seven (NS50L)
NanoSIMS 50
Conventional and co-axial probe
forming systems
Any design of a SIMS instrument must accommodate two conflicting needs: the objective lens of the primary ion
column must be as close as possible to the sample in order to optimize its optical properties, leading to small
and intense ion beam.
On the other hand, secondary ions are emitted in a half-space, with a large energy spectrum (~ 0-200eV). In
order to collect as a large fraction of these ions as possible, the extraction optics should also be placed as close
as possible to the sample. As the extraction and objective optics have their own physical size, a compromize
must be found leading to large sample/optics distances. The NanoSIMS design has escaped from this dilemna
by switching to a totally new co-linear optics capable of simultaneously focusing the primary ions with high
quality, and collecting most of the secondary ions.
Primary beam
Primary beam
Secondary beam
Secondary beam
Deflection
plates
Probe
forming
optics
Extraction
optics
Extraction
and probe
forming
optics
Sample
Conventional
SIMS
Sample
Co-axial
NanoSIMS
Advantages of co-axial configuration :
• Short working distance of the probe forming lens/ extraction
1) smaller spot size for a given beam current
2) higher collection efficiency and dramatical reduction of the broadening of the
secondary ion beam due to the initial angular and energy distribution.
This will favour transmission of the analyzer at high mass resolution.
• Minimization of shadowing effects for non flat surfaces; hole or trench bottom analysis
capability
• Obtention of deep craters of small size
• Reduction of the beam and raster distorsion
Constraints due to co-axial configuration :
• Primary and secondary ions must be of opposite polarity and equal energy (Cs+/ negative
ions, O-/ positive ions). This excludes MCs+ technique and the use of O2+ ions for
electropositive elements.
• Oxygen flooding can not be used
NanoSIMS 50
Lateral resolution with cesium
The use of cesium primary ions is mandatory in SIMS for the analysis of electro-negative elements (H, C, O, N, F, Cl, P
, Ge, Se, As, Br, Te, I, Au…). It enhances the ionization yield (= sensitivity) by several orders of magnitude compared to
non-reactive primary species (Ar, Ga, Au, Bi…).
The NanoSIMS is equipped with the patented CAMECA Microbeam cesium ion source, guaranteeing the highest
brightness available among commercial cesium ion sources. The source brightness (in mA/sr/cm2) measures the ion
current available within a given solid angle from a given source area. It is an invariant in optics: a perfect (= without
optical aberration) primary ion column could at maximum re-obtain this brightness in the final spot size. The high
brightness of the ion source, the short final objective working distance, its reduced aberration coefficients, and the
normal incidence guarantee the best performance available from a SIMS microprobe for electronegative secondary ion
microanalysis.
Beam spot size (= lateral resolution) is determined by extracting the 16%-84% intensity line-scan from a SIMS image of
a TiCN sample giving sharp grain boundaries without artifact. Condition: 16 keV Cs+, negative secondaries.
12C
2
12C14N
300nm
300nm
Field: 4 X 4 µm, 512X512 pixels, Acq time: 30min.
12C
2
12C14N
Measured lateral
resolution: 25nm
200nm
200nm
Field: 2.5 X 2.5 µm, 256X256 pixels, Acq time: 22min.
Conservative spot size specification (16-84%) for Cs+ :
50nm/0.3pA, 100nm/2pA.
NanoSIMS 50
Sample by courtesy of LAM, Luxemburg
Lateral resolution with oxygen
The NanoSIMS is equipped with the high brightness CAMECA duoplasmatron ion source. Although it can
generate positive ions (02+), it is mainly used in the NanoSIMS to generate 0- ions. Due to the opposite
polarity scheme, one can benefit from the strong ionization enhancement of electropositive elements with
oxygen implantation. Additionally, the use of primary negative ions offers the well-known advantage of much
lower sample charging problems compared with positive primary ions (the sample always tends to charge
positively due to the secondary electron emission).
The beam spot size is determined by extracting the 16%-84% intensity line-scan from a
recorded here on a sample containing Al grains.
27 Al+
27Al+
100%
Intensity (A.U)
84%
O-: 0.3pA,
16-84% < 170 nm
16%
0.0
1.0
Distance (microns)
2.0
Field: 7.5 µm x 7.5 µm, 16-84% spot size: 170 nm, O-: 0.3pA
27Al+
Intensity (A.U)
100%
84%
O-: 2pA,
16-84% < 340 nm
16%
0%
0.0
1.0
2.0
Distance (microns)
Field: 10 µm x 10 µm, 16-84% spot size: 340 nm, O-: 2pA
Conservative spot size specification (16-84%) in O- :
200nm/0.3pA, 400nm/2pA.
NanoSIMS 50
O2- current specs typically four time lower than O-.
SIMS image
Analyzer Transmission
versus Mass Resolution
T (%)
100
68
65
56
51
45
39.9
29
24.5
Without any slit, mass
resolution is 3500 and
transmission is taken as
100%. Other transmissions
are referred to this one.
100
90
relative
transmission
Relative
Transmission
MRP
3500
5910
6120
6770
7120
7390
7885
9470
9615
80
70
60
50
40
30
20
10
0
2000
3000
4000
5000
6000
7000
8000
9000
10000
mass resolving power
Mass Revolving Power
Mass resolution is taken as M/dM = R/4 * L10-90, where R is trajectory radius
and L10-90 is line width corresponding to 80 % of intensity
Optimized for lateral resolution and sensitivity, the NanoSIMS is a pure ion Microprobe (scanned
focused ion beam) and has no ion microscope mode (transport of a stigmatic, magnified mass
filtered ion image) as on the CAMECA IMS analyzers.
One of the characteristics of the NanoSIMS is to work in high mass resolution: by design, there is
no low mass resolution mode on the NanoSIMS, even when removing all apertures.
In addition, the analyzer transmission is maintained very high (see plot above), even when
increasing the Mass Resolution. This is the result of:
- a very high, normal extraction field allowing a very early secondary ion focusing,
- a limited field of view together with a dynamic emittance matching,
- a careful transport and rectangular shaping of the secondary beam resulting in
the use of small slit compared to the magnet size, reducing aberrations,
- the correction of the second order mass spectrometer optical aberrations.
NanoSIMS 50
NanoSIMS 50 main options
NEG. Normal incidence Electron flood Gun for the analysis of strong electrical insulators in Cs+ with
negative secondary ions, when gold coating method is not sufficient, at high beam current.
SED. Secondary Electron Detector. Works in negative secondary polarity with cesium. Can give
nicely contrasted topographical images for illustration and sample visualization.
Full-MDA. Motor Driven Apertures. Automation of diaphragms, apertures and hexapole for an
easier operation, a better reproducibility and a higher throughput.
Z-motor. Automation of the sample stage Z-axis. Allows to re-adjust the sample Z position for
highest precision isotopic measurements in geochemistry, in unattended chain acquisition mode.
Geo-Faraday. Low-noise FC electrometer for geological applications in single FC-EMs mode.
Dual-Faraday. Special trolleys #1 & #2 derived from NS50L design, equipped with both E.M. and
F.C., allowing FC-EMs as well as FC-FC-EMs acquisition modes.
LD. Large Detector. Equipped with continuously adjustable exit slit and electrostatic sector.
NanoSIMS 50
Note: all options are field-retrofittable
NanoSIMS 50L
The Multicollection analyzer of the
NanoSIMS 50 can measure five masses with two key characteristics:
1) Mass Dispersion (Mmax/Mmin in a parallel acquisition)
= 13.2 (or 14.4 with LD option).
For ex, one can follow 12C on trolley #1 and get mass 12 x 13 =
156amu on the fixed detector #5 at large radius.
in
m
Ex: 27, 28, 29, 30amu can be analyzed simultaneously but 57,
58, 59, 60amu require two acquisitions: 57 & 59 then 58 & 60.
3.2
30
M/
8mm
a
Mm
/M
x
=1
2) Due to the finite width of the detectors and their
angle relative to the focal plane, the minimum Mass
Interval between two adjacent detectors is M/30.
NS50
The NanoSIMS 50L receives a larger Multicollection analyzer improving several specifications:
- with the introduction of exit cylindrical sectors, the Mass Separation between adjacent detectors is M/58.
- the magnet size is enlarged in order to reach a Mass Dispersion Mmax/Mmin = 21.
- seven masses can be measured in parallel (five on the NS50)
- each trolley can be equipped with E.M. and FC (switch at atmospheric pressure, multicollection opened).
NS50L
M/58
Mmax/Mmin = 21
Side view of four trolleys of the
NS50L multicollection
7 masses in parallel (ex: all O and Si isotopes in parallel, or 50-52-53-54Cr + 51V +48Ti + 55Mn)
Up to 58Fe in multicollection and single mass separation (Ti, Cr, Mn, Fe isotopes accessible)
Multiple Faraday Cup option.
NanoSIMS 50
NanoSIMS 50/50L
The NanoSIMS 50L mainly differs from the NS50 by its larger multicollection and associated larger turbo-pump. Some
other, minor differences: the Z-motor, optional on the NS50, is standard in the NS50L, and the LD large detector
option of the NS50 is not available on the NS50L.
The general size of the instrument is not changed dramatically as can be seen from photos below:
Standard NS50
NS50L
NS50L
NanoSIMS 50
New options: FullFull-MDA (NS50/50L)
and MultiMulti-Faraday (NS50L)
1) Full-MDA: the NanoSIMS 50 and 50L can both be equipped or
retrofitted with the automation of D0 and D1 diaphragms, entrance,
aperture and energy slits, hexapole centering, and individual trolley
exit slit exchange. The benefits are an easier operation (important
specially for multi-user operation), a better reproducibility for high
precision isotopic ratios and a higher throughput (ex: pre-sputter at
high current followed by analysis at high resolution in a chain
analysis).
Automated D0
primary diaphragm
Energy Slit
Entrance & Aperture
Slits
Z-axis of the sample
stage
D1 co-axial lens
diaphragm
Automated exit slit exchange
2) Multi-Faraday: the new trolleys of the NanoSIMS 50L can be equipped simultaneously with E.M and F.C. The
standard Multi-Faraday option includes 7 E.Ms and 3 FCs. More trolleys can be equipped with FC and associated
pre-amp, on request, up to a maximum of 7 EMs and 7FCs. The EM/FC selection is done multicollection opened at
atmospheric pressure by mechanically sliding the detector behind the exit slit.
Thermostated low-noise Multiple FC
preamplifier chamber allowing
intercalibration of the FC signals.
Synoptic of NS50L Multi-Faraday option
FC
EM
NS50L detector trolley showing scanning
plates, exit slit mechanism, cylindrical
sector and detectors (EM and FC)
NanoSIMS 50
NanoSIMS sample mounting 1/2
The standard NanoSIMS holder is 50mm in diameter. The front plate can be customized depending on the user needs. Sample
thickness can be up to 9mm. The sample surface must be flat. The Z movement of the sample stage can be used to keep
sample/extraction distance at 400µm +/- 50µm. Due to the small sample-lens distance, the sample must not degas too much in
order to avoid risks of arcing. Typical working condition is in the E-9/ E-10 torr range. We thus recommend to minimize, if any, the
embedding material volume. Gold coating of the sample is generally used in order to reduce sample charging problems.
Below is a schematic of a NanoSIMS sample holder with 10mm holes (different hole sizes are available), with parts giving an idea of
some possible mountings. For an easier viewing, the schematics are not at scale.
PARTS
0.1mm
SOME SAMPLE MOUNTINGS
Attention! If rectangular sample, check
its diagonal to be less than 10.4mm !
Ø9mm
Thin flat sample glued or fixed with non-degasing
(< 1E-9 Torr) conductive double-side sticky tape
Ø10.4mm+0, -0.05
Ø10mm+0, -0.1
Part of the sample holder.
Material: ARCAP AP4
Ø10mm+0, -0.1
variable
Intermediate ring.
Material: ARCAP AP4
4mm
Gold film
Metallic cylinder.
Material: ARCAP AP4
Part #: 45620693
Thin plate with holes.
Four holes of diam. 3mm.
Material: Z2-CN18-10,
Part #: 45620694
Ø9mm
4mm
Ø10mm+0, -0.1
0.1mm
Ø10mm+0, -0.1
Thicker flat sample glued or fixed with non-degasing
(< 1E-9 Torr) conductive, double-side sticky tape
Embedding ring.
Material: ARCAP AP4, Part #: 45620692
Attention! If rectangular sample to be embedded,
check its diagonal to be less than 9mm !
Small particles pressed into a gold foil
Amagnetic Spring
Small sample(s) analyzed through the
holes of the thin top « grid » or « plate »
EOS
EOP
0.3mm
Metal
cylinder
EOW
Sample
holder
same
potential
Coaxial optics showing the short working distance
NanoSIMS 50
Embedding in high vacuum resin or metal in metallic cylinder,
then polished (or not if it is flat) and gold coated if needed.
Ex: Korapox 439 epoxy (www.koemmerling-chemie.de),
Varian Torr Seal Low Vapor Pressure Resin (www.varianinc.com).
Also used: Wood metal (In-Bi alloy melting at 78°C)
NanoSIMS sample mounting 2/2
50mm/ 2-inch diameter
« Geology » sample holder
with one 1-inch , two halfinch and two 10mm holes.
Ref #: 45620643
25mm/ 1-inch diameter
«Standard» sample holder
with four 10mm holes.
Ref #: 45620641
50mm/ 2-inch diameter
«Biology» sample holder
with eight 10mm holes.
Ref #: 45620642
Shuttle
Ref # : 45621551
It is possible to simultaneously load two shuttles on the
NanoSIMS sample stage : two 1-inch sample holders, or
one 1-inch and one 2-inch sample holder. Note that the
second 1-inch sample holder can be brought in SIMS
position but not in the optical microscope position. It is
generally used to store standard samples.
The NanoSIMS is delivered with eight shuttles and nine
sample holders: two “standard”, five “biology” and two
“geology”. The respective numbers can be modified on
request at the time of order.
Reverse view of the « Biology» sample holder, unscrewed
from its shuttle. One can see the springs pushing the
sample cylinders in their hole against their lips.
Ex. of wrong mounting ! Must be
remounted with front reference.
Thin samples (ex: biological sections)
must be deposited on the POLISHED
side of the metallic cylinder !
Biological thin cross-section
deposited on 7.3x7.3mm silicon
square (diagonal=10.3mm).
Sample under 4hole thin plate
Embedded
sample
10mm diam.
embedding ring
Ref #: 45620692
10mm metallic cylinder
Ref #: 45620693
Embedded
sample
4-hole thin plate
Ref #: 45620694
NanoSIMS 50
Finger contacting the front
electrode of the objective lens.
CORPORATE HEADQUARTERS
CAMECA
29 Quai des Grésillons
92230 Gennevilliers - France
Tel.: +33 1 43 34 62 00
Fax: +33 1 43 34 63 50
Web-site: www.cameca.com
NanoSIMS 50
CAMECA Germany
Bruckmannring 40, D-85764
Oberschleissheim - Germany
Tel: +49 89 315 891-0,
Fax: +49 89 315 59 21
CAMECA Instruments, Inc.
204 Spring Hill Road
Trumbull, CT 06611-1356 - U.S.A.
Tel.: +1 203 459-0623
Fax: +1 203 261-5506
CAMECA Instruments Japan K.K.
7F, Sumitomo Ikebukuro Ekimae Bldg.
Higashi-Ikebukuro 1-10-1
Toshima-ku, Tokyo 170-0013 - Japan
Tel.: + 81 35 396 0991
Fax: + 81 35 396 0980
CAMECA Korea C°., Ltd.
4F, 1045-7 Youngtong-dong
Youngtong-Ku, Suwon-city
443-813 Kyunggi-Do - Korea
Tel.: + 82 31 202 6344
Fax: + 82 31 202 6347
CAMECA Taiwan Corp. Ltd.
A2, 10F-6, No. 120, Sec. 2, GongDaoWu Rd.
30056 Hsin Chu, Taiwan (R.O.C)
Tel: + 886 3 5750099
Fax: + 886 3 5750799
NS50_instrumentation_may2006
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