1. nanoSIMS: a new analytical tool for ultra-fine feature analysis using secondary ion emission
R. Stern* and Peta Clode
The University of Western Australia
Centre for Microscopy and Microanalysis

3. nanoSIMS labs
#10

4. SIMS Secondary Ion Mass Spectrometry
probing analytical technique for measuring the surface or near surface chemical or isotopic composition of solids
uses probe ions to sputter target ions in laterally microscale or smaller regions (ion microprobe)
analytical characteristics:
nm depth resolution
lateral resolution 10’s nm to mm
most sensitive of the probing analytical techniques, ppb-ppm
entire periodic table, H to U
simple sample preparation
Although the instrument is new, the analytical technique has been widely utilized for decades
This of course is SIMS or secondary ion mass spectrometry.
The NanoSIMS is a specialized form of ion microprobe.

5. SIMS Data Basic Dimensions: 1 dimension 2 dimensions 3 dimensions
ratios 18 16 O/ O
24Mg/28Si
Mass spectrum
cps,ppm Se
Basic
from tiny mass consumed
Dimensions:
1 dimension
‘depth profile’: composition along a line normal to the surface
‘line scan’: composition along a line parallel to the surface
2 dimensions
‘image’ (map) of the surface distribution of secondary ion species
3 dimensions
a stacked series of secondary ion images collected at discrete depths into the target
Image
Depth profile
Line scan

6. SIMS analytical Energy Analyzer Mass Analyzer Ion source Secondary ion
Collection Optics
Detector
Primary ion column
The typical layout of a SIMS instrument is shown here. There are two basic components: the ion probe and the analyzer.
The ion probe comprises a source of ions ( O,Cs,Ar,Ga), a column to accelerate and focus the primary ions to a fine spot, and the sample under vacuum.
As a consequence of bombarding the sample with primary ions, secondary ions of the target (which must be a solid) are produced, and these are subsequently analyzed within the second major component, the mass analyzer, or more technically, the secondary ion mass spectrometer. The analytical technique is thus commonly referred to as SIMS. .
Sample
under
vacuum

7. High mass resolution analyzer
Detector array: 5 isotopes acquired simultaneously
Ion sources: O-, Cs+
Normal, co-axial primary & secondary ions
samples
Sample introduction

8. Features of NanoSIMS dynamic SIMS probe lateral resolution
for bulk sample ion chemical/isotopic characterization
not for molecular identification or oxidation state
probe lateral resolution
50 nm for 133Cs+
200 nm for 16O-
ability to scan the primary beam and record secondary ion images at ultra-fine-scale lateral resolution
very low eroson rate, ~nm/hr (sample preservation)
simultaneous multicollection of up to 5 isotope species
routine high mass resolution
resolve isobaric interferences

9. Ion imaging of TiCN alloy demonstrating sub-50 nm edge resolution with Cs+
3 x 3 um, 26CN
10 x 10 um, 24C2

10. BIOMATERIALS Engineered Materials Minerals Semiconductors
Ceramics
Alloys
Minerals
Extraterrestrial dust
Geochronology
Ore minerals
BIOMATERIALS
sub-cellular imaging
biochemical function
cancer research
pharmaceuticals

11. NanoSIMS labs bio-SIMS program
0. Harvard Medical School/ MIT, Boston USA National Resource for Mass Spectrometry Imaging, NIH NCRR
1. Washington University, Saint Louis, MO
2. Max Planck Institute, Mainz, Germany
3. Institut Curie, Paris, France
4. Oxford University, U.K
5. Lawrence Livermore National Lab, Livermore, CA, USA University of California, Davis
6. National Institute for Materials Science, Tsukuba, Japan
7. LAM, Centre de Recherche Public-GL, Luxembourg
8. ExxonMobil, New Jersey, USA
9. University of Tokyo
10. The UWA
11. Rouen Univ, France
bio-SIMS program
bio-SIMS program
bio-SIMS program

12. Non-metallic elements used in SIMS biological analysis
Naturally-occurring isotopes
12C – all cell organelles
14N – DNA, RNA, proteins
31P – DNA, RNA (nucleic acids)
32S – proteins
Artificial isotopes (stable or radioactive)
14C – turnover/pathways of C
15N – turnover/pathways of labelled amino acids (proteins), nucleic acids
17F – Fluoracil, cancer drug targetting chromosomes
81Br – in Bromodeoxyuridine (BrdU), specifically incorporated into DNA during DNA synthesis
123, 125, 127I – in Iododeoxyuridine

13. Examples of metallic elements used in SIMS biological analysis
Li, Na, K, Rb, Cs
Be, Mg, Ca, Sr, Ba
Ti, Cr, Mn, Fe, Ni, Pb, Al, In
Au, Ag
Sc, lanthanides, actinides
to date, few studies, poor sensitivity and spatial resolution

14. O- primary ion bombardment, positive secondary ions, and a silicon matrix

15. Cs+ primary ion bombardment, negative secondary ions, and a silicon matrix
Compared to other probe techniques, SIMS has the highest sensitivity.

16. Sample preparation
must be dehydrated, +/- fast freezing, chemical fixation (glutaraldehyde, Os tetroxide), epoxy embedding, cryo-sectioning (0.3 – 1 µm)
will feature of interest be preserved?
other documentation techniques to map features (confocal, VPSEM, TEM, etc.)
Example of human hair cross-section deposited on Si (Hallegot and Corcuff, 1993)
Scanning electron microscopy images
cortex
cuticle
Important to emphasize that the N50 should not be used for mapping internal structures of cells, which can be done by other methods (confocal microscopy, TEM, SEM, etc). The idea is to use the instrument for process tracing, particularly using tagged molecules in experimental conditions.

17. nanoSIMS samples Sample holder for 1 cm samples
Thin membranes on Si wafer

18. Imaging of resin embedded biological tissues
12C14N
32S
A mucous-producing cell in coral tissue
Scale = 3um
Primary ions: Cs+
150 mm
12C14N
31P
A symbiotic algae in coral tissue
Scale = 2um
Primary ions: Cs+

19. Imaging isotopic tracers in resin embedded biological tissues
150 mm
44Ca / 40Ca
44Ca used as a tracer of calcium (40Ca) to determine pathways of movement & uptake 1. 2. 3.
Region
44Ca/40Ca
Natural abundance
0.02
1. Mucous cell
0.05
2. Spiked Seawater
0.7
3. Epithelial cells
0.37
4. Stinging cell 4.
Coral epithelium
44Ca 1 min
Scale = 5um
FOV = 35um
Primary ions: O-
Significant
44Ca
uptake

20. Mouse cochlea cells

21. Imaging of As within human hair
Audinot et al. (2003)
Heavy metal exposure
An example of where the NanoSIMS is capable, but can be done with other instrumentation, and therefore not particularly cost effective

22. Analytical Issues: will the metal ions be detectable?
are there non-metallic ion labels that can be used as proxies for the metals?
quantitation: how important?
sample preparation to avoid element migration or loss

23. nanoSIMS & ARC Metals in Medicine
is capable of playing a vital role
the analytical capabilities and experience with metals in biological media needs to be developed
R. Stern and P. Clode are here to enter into research partnerships with you