Transcript Kein Folientitel

High Resolution Surface Mass Spectrometry
by
TOF-SIMS
 The challenge of chemical nanoanalysis
 Secondary Ion Mass Spectrometry - SIMS
 Analytical application of TOF-SIMS
 Perspectives
Key questions in nanoanalysis
• Identification (What?)
• Localisation (Where?)
• Quantification (How much?)
Nanotechnology
Definition:
In at least one dimension <100nm
Example:
Surface mapping
Lateral resolution: 100 nm
Information depth: 1 nm

Volume:
Amount of material:
1x100x100 nm3
0.1 attomole
some 10.000 molecules
Chemical information ?
• Proximity probes (AFM, SNOM, ..... )
• Electron emission based probes (XPS, AES, TEM, ….)
• Surface mass spectrometry
Excitation by:
 Electrons
 Electrical fields  Atom probe
 Photons  MALDI
 Ions  Secondary Ion Mass Spectrometry (SIMS)
Ag catalyst
Secondary Ion Emission
M  Xiq
X1+, X2+, X3+, ...... Xi+, ...............
X1-, X2-, X3-, ....... Xi-, ...............
X1o, X2o, X3o, ....... Xio, ...............
Transformation probability : P (M  Xiq)
Static SIMS
 Negligible probability of bombarding a damaged area
 Sputtering of only a negligible fraction of the uppermost monolayer
 Reduction of the primary ion current (fluence)
 Reduction of the secondary ion current
 Resulting conditions/requirements
 High transformation probabilities
 High transmission mass spectrometer
 High sensitivity secondary ion detection
Monolayer Sputtering
θ(t) = θ(0) . exp (- σ .ν . t)
θ(t)
σ
ν
θ(0)
Fractional coverage at time t
Damage cross section
Primary ion flux density
Fractional coverage at t = 0
Lifetime t of one Monolayer θ(t) = θ(0) . 1/e
t = 1/( σ.ν)
Ag catalyst
Ag catalyst
ML sputtering
 = 1,34. 10-14 cm2
Example: octanethiol on Au
X10
4
I
N( t )  N( t 0 )  exp( 
 t)
eA
Static SIMS
counts / 100s
4
3
I = 0.6 pA
A = 1.56 10-4 cm2
= 134 10-16 cm2
2
0
500
1000
1500
time in s
2000
2500
Mass analysers applied in Static SIMS
(Historical development)
Magnetic sector field

Quadrupole

(FT-ICR)

Time - of - Flight
TOF-SIMS
Main features of TOF-SIMS
 Parallel mass detection
 High (unlimited) mass range
 High mass resolution > 10 000
 High mass accuracy (1-10 ppm)
 High transmission for high masses and at high mass resolution
 All elements and isotopes
 Molecular species
 High sensitivity (ppb, attomole)
 High lateral (50 nm)and depth (1nm) resolution
Static SIMS
Oxidized and contaminated
molybdenum surface
(1973)
Molecular Information by Static SIMS
Example: Polystyrene
I Intact Molecules (m < 10,000 u)
(M+H)+, (M+Ag)+, (M+Na)+,
(M-H)-, ...
(“substrate cationization” only from
(sub)monolayer coverages)
II Characteristic Large Fragments
loss of functional groups,
repeat units,..…
(according to “classical”
fragmentation rules)
III Small Organic Fragments
end groups, fractions of repeat units,
side chains,.…
(sufficient for identification)
Static SIMS
Phenylalanylglycine
ML on Ag
(1981)
Cyclosporine A
Conservation of charge signe
- Examples -
Al-oxide
 Al+, O-, AlO+, AlO2-, .....
Ag-sulfate
 Ag+, SO4- , ........
M on Ag
 M+H+, M-H-, M+Ag+, ......
Me-Cs
 Me-, Cs+, .......
Transformation probabilities (M  Xiq)
-Examples -
Al
P (Al  Al+)
= 0,007
Al-oxide
P (Al  Al+)
= 0,7
Ag-sulfate
P (-SO4  SO4-) = 0,3
Me - Cs
P (Cs  Cs+)
= 1,0
Ag - Methionine
P (MM+H+) =
Ag - Bradikinin
P (MM+H+) = 0,0001
(1.060 amu)
Ag - Mellitin
P (MM+H+) = 0,000 000 5
(2.846 amu)
0,005
Damage cross sections σ
- Examples -
System
σ/10-14cm2
d/nm
Ni - O
Ni - H
Ni - H2
0,25
0,5
4,5
0,5
0,7
2,1
Au - Thiole
1,3
1,1
4,5
20,0
45,0
2,3
4,9
7,4
Ag - Methionine
Ag - Bradikinin
Ag - Melittin
(1.060 amu)
(2.846 amu)
Sample materials, geometries, operation modes
 Sample materials
 Metals, Semiconductors, Oxides,
 Glasses, Ceramics,
 Polymers, Additives, Biopolymers, Biomolecules
 Biological tissues
 Sample geometries
 Surfaces, Monolayers, Particles, Fibers, .....
 Operation modes
 Spectroscopy
 Imaging (mapping)
 Depth profiling
 3D-analysis
TOF - SIMS activities
 250 laboratories are operating TOF-SIMS instruments worldwide
 Bienniel International SIMS Conferences
2005: SIMS 15 (Manchester)
2007: SIMS 16 (Japan)
(350 – 450 participants)
 Bienniel European SIMS Conferences in Münster, Germany
2006 : SIMS Europe V
(200 – 250 participants)
(Static) SIMS Optimisation
 Mass Spectrometry
Magnetic sector field  Quadrupole )  (FT-ICR)  Time-of-Flight
 Lateral resolution
Focused ion beams
 Depth resolution
Cluster bombardment
Low energy PI
 P(MX)
Oxidation, Cs deposition
Nobel metal substrates
Cluster bombardment
Mass resolution, accuracy
Lateral resolution
Example: Photographic Crystals
16 %
lateral distribution of Clon cubic silver halide crystals
84 %
line profile
x16%-84% = 50 nm
(Sample provided by the University of Antwerp, Belgium (Prof. Gijbels))
Deth resolution
B monolayer in Si
4
10
30
Si
20
10
11
B
19
Intensity
intensity
10
2
10
12
C
18
10
1
3
10
17
10
0
10
3
B concentration / atoms/cm
(atoms/cm
B-concentration
)
3
10
0
5
10
15
depth / nm
depth (nm)
20
25
Influence of the Substrate and the Surface Coverage
Yiel
d
Cluster bombardment
O  Ar  Xe  SF5  CmHn  C60
Ga  Aun  Bin
1
3
5
7
Number of Layers
O
C
+
-2
(C2H2O2)-
10
OH
C6F6
+
+
C10F8
+
C10H8
Au2
+
C7H7
Yield (219 u)
CH3
+
SF5
-3
10
+
CO2
Au
+
+
Xe
+
O2
Ar
+
-4
10
O
0
+
50
100 150 200 250
Primary ion mass (u)
300
350
400
Main features of TOF-SIMS
 Parallel mass detection
 High (unlimited) mass range
 High mass resolution > 10 000
 High mass accuracy (1-10 ppm)
 High transmission for high masses and at high mass resolution
 All elements and isotopes
 Molecular species
 High sensitivity (ppb, attomole)
 High lateral (50 nm)and depth (1nm) resolution
Trace Metal Detection / mass resolution
30SiH2O
Ti
SiC2
2
Intensity
10
101
102
48.05
mass (u)
51.95
52.05
mass (u)
coverage (atoms/cm2):
Ti:
6.1E10
Cr:
8.2E09
Fe:
3.1E09
Cu:
2.1E10
103
Fe
Si2
63Cu
4
SiCl
Intensity
10
Cr
101
47.95
105
mass resolution (FWHM):
Ti:
13119
Cr:
12813
Fe:
12009
Cu:
13849
103
103
102
10
2
101
101
55.95
data taken from 003_r.dat
56.05
mass (u)
62.95
63.05
mass (u)
TOF-SIMS Detection Limits
Element
7
detection limits
detection limits
(atoms / cm2)
(atoms / cm2)
1E7
52
1E8
11
B
5E7
55
1E9
Na
1E7
56
2E8
24
2E7
58
1E9
Al
2E7
Co
2E8
39
1E7
63
3E8
40
3E7
69
1E9
48
2E8
*
3E9
51
2E8
98
Li
Mg
K
Ca
Ti
V
Cr
Mn
Fe
Ni
Cu
Ga
As
Mo
6E9
1 Monolayer = 1.5E15 atoms/cm²)
 the error is estimated to be within a factor of 2 to 3.
Depth profiling
4
10
4
30
10
Si
30
20
Si
10
11
B
11
19
Intensity
intensity
10
2
10
12
C
18
10
1
3
10
B
3
10
7
Li
intensity
10
3
B concentration / atoms/cm
(atoms/cm
B-concentration
)
3
Na
2
10
12
C
1
10
17
10
0
10
0
10
0
5
10
15
depth / nm
depth (nm)
20
25
0
5
10
15
20
25
depth / nm
depth (nm)
Reconstructed profile (Li, Na)
Material Science
2D Images and Cross Sections
+
Mg
+
Ga
+
Sr
Surface
20 nm
Bulk
595 nm
Crossection
zy View
(Sample provided by Prof. Martin, RWTH Aachen, Germany)
+
Cr
+
Fe
+
Y
Surface Imaging
Blooming Effect on Polymer
Field of View: 284 x 284 µm2
Polymer (PP)
Melt Stabiliser
Antioxidant
Polymer, Stabiliser, Antioxidant
Particle Analysis / Uranium
Nanoextraction
Laser-SNMS
1µm
1µm
1µm
overlay
TOF-SIMS
1µm
1µm
overlay
LB-multilayer system: Lipids: DPPC/DPPG (4:1), Protein: 0.4 mol% SP-C
Phase Separation
Lipid
Protein
10 µm
LaserSNMS
FLM
dye-labeled lipid
58: C3H8N
30: CH4N
10 µm
TOFSIMS
+
AFM
topography
58: C3H8N
110: C5H8N3
Au2 imaging - Placenta cell complex
Mouse Brain Section
Correlation Analysis: 3 Colour Overlay
Field of View: 8 x 8 mm2
Fe
sum of
phospholipid ions
corpus
callosum
caudate
putammen
canterior
commissure
sum of
cholesterol ions
nucleus
triangularis
septi
Example provided by Alain Brunelle,
ICSN, CNRS, France
Rat Brain CrossSection
Field of View: 18 x 18 mm2
255
283
771
892
Carboxylate
C18 Fatty acid
Phospholipid
Triclyceride
to be published by A. Brunelle et. al. ICSN, CNRS, France
Salbutamol
Field of View: 52.7 x 52.7 µm2
one pixel: 100 x 100 nm2
– only 100 shots applied
– 20 integral counts
x100
Intensity
6.0
Salbutamol
5.0
4.0
3.0
2.0
Salbutamol (M+H)+
max counts: 20
180
190
total counts: 2.12 x 105
 2 x 10-20 mole detected from a 100 nm spot
200
210
220
230
240
250
mass (u)
Applications in Life Sciences
 Fundamental research
Tissues, cells, membranes, biopolymers, lipids, ......
Biomedicine, biology, biochemistry……….
 Diagnostics
Biochips, chromatographies, nanofluidics, marker, molecular
pathology, ……..
 Drugs
Delivery systems (tablets, nanoparticles, polymers,..), localisation
in cells and tissues (ADME), contamination, screening, ......
 Biomaterials
Artificial membranes, substrates for cell growth and artificial
tissues, protein- and cell-adhesion, biocompatibility, .....
Directions of future development
 Fundamental research
Understanding the secondary ion formation process
Experimental and theoretical model systems
UHV experiments
 Technical development
Sensitivity:
Impact cascade, chemical environment, Laser-SNMS, ……..
Lateral resolution: Spot size, impact cascade
Depth resolution: Impact cascade
 Instrument development
New cluster ions (N,O,He, metals, .... )
Cluster FIB
Laser-SNMS
 Analytical application
Nanoelectronics and nanomaterials
Nanobioanalytics
Nanoparticles
Transformation probabilities 1
Δl below10nm (control of beam diameter and impact cascade)
Moleculare 3D-analysis
Selective bonding and yield control
Some challenges in molecular nanoanalysis
 Single Molecule Detection / Identification
Subattomol-Analytics, sample fixed in a well-defined surface area
 Individual Cell Analysis
Chemical content of a single cell (ML separation)
 SIMS Chip
Chip-arrays for selected molecular species (or classes of molecules)
Microstructured and -functionalized surfaces (separation, yield optimisation)
Selective bonding and yield control
 Zeptomole Detector
TLC, Gelchromatography , Isotachophoresis, .......
 Nanoproteomics
Immobilysed enzymes (trypsine)
 Moleculare Pathology
Electron microscopy  Imaging TOF-SIMS