Rutherford Backscattering & Secondary Ion Mass Spectrometery
Transcript of Rutherford Backscattering & Secondary Ion Mass Spectrometery
Advanced Materials Characterization WorkshopJune 3 and 4, 2013
University of Illinois at Urbana-Champaign | Materials Research Laboratory
© 2013 University of Illinois Board of Trustees. All rights reserved.
Rutherford Backscattering & Secondary Ion Mass Spectrometery
Timothy P. Spila, Ph.D.
Frederick Seitz Materials Research LaboratoryUniversity of Illinois at Urbana‐Champaign
© 2013 University of Illinois Board of Trustees. All rights reserved.
Rutherford Backscattering Spectrometry
He+
He
RBS is an analytical technique where high energy ions (~2 MeV)are scattered from atomic nuclei in a sample. The energy of theback-scattered ions can be measured to give information onsample composition as a function of depth.
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Geiger‐Marsden Experiment
Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.
Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated positive charge.
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Rutherford Backscattering Spectrometry
2 MeV Van de Graaff accelerator
beam size Φ1-3 mmflat samplecan be rotated
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Primary Beam Energy
thin film projected on to a plane: atoms/cm2
Figure after W.‐K. Chu, J. W. Mayer, and M.‐A. Nicolet, Backscattering Spectrometry (Academic Press, New York, 1978).
(Nt)[at/cm2] = N[at/cm3] * t[cm]
ener
gy lo
ss p
er c
m lo
g(dE
/dx)
1 keV 1 MeV(log E)
1 keV 1 MeV
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Elastic Two‐Body Collision
22 22 sin cost i i
i t
MMMKM M
E1 = KEo
M1<M2, 0 ≤θ≤180o
RBS: He backscatters from M2>4
0 ≤Φ≤90o
0 50 100 150 2000.0
0.2
0.4
0.6
0.8
1.0
= 150o
He4
Kin
emat
ic fa
ctor
: K
Target mass (amu)
M1vo2 = M1v1
2 + M2v22
M1vo = M1v1 + M2v2
Elastic Scattering
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Rutherford Scattering Cross Section
2 241 2 21
2( , ) sin ( ) 2( )
4 2RZ Z ZME ME E
Coulomb interaction between the nuclei:exact expression -> quantitative method
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Electron Stopping
Figure after W.‐K. Chu, J. W. Mayer, and M.‐A. Nicolet, Backscattering Spectrometry (Academic Press, New York, 1978).
1 keV
ener
gy lo
ss p
er c
m lo
g(dE
/dx)
1 MeV(log E)
© 2013 University of Illinois Board of Trustees. All rights reserved.
RBS – Simulated Spectra
Element (Z,M): O(8,16), Al(13,27), Ti(22,48), In(49,115), Au(79,197)
hypothetical alloy Au0.2In0.2Ti0.2Al0.2O0.2/C
Au
In
TiAlO
C10 ML 100 ML Au
In
TiAlOC
1200 8000
Au
In
TiAlOC
1000 ML16000
22( , )R
ZEE
0 50 100 150 2000.0
0.2
0.4
0.6
0.8
1.0
= 150o
He4
Kin
emat
ic fa
ctor
: K
Target mass (amu)
4000 ML 10000 ML20000 50000
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SIMNRA Simulation Program for RBS and ERD
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Thickness Effects
Series 0Series 1
Channel700650600550500450400350300250200150100500
Cou
nts
11,500
11,000
10,500
10,000
9,500
9,000
8,500
8,000
7,500
7,000
6,500
6,000
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Energy [keV]
N surface
300 nm
Ti surfaceTi interface
N, O, Mginterface
Series 0Simulated
Channel700650600550500450400350300250200150100500
Cou
nts
14,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Energy [keV]
Ti surface
400 nm
Ti interface
N, O, Mginterface
N surface
Series 0Simulated
Channel700650600550500450400350300250200150100500
Cou
nts
14,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Energy [keV]
600 nm
Ti surface
Ti interface
N, O, Mginterface
N surface
TiN/MgO
N
He
DScattered
15
15
Incident
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Incident Angle Effects
TiN/MgO
Series 0Simulated
Channel700650600550500450400350300250200150100500
Cou
nts
14,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Energy [keV]
Ti surface400 nm
Ti interface
N, O, Mginterface
N surface
Series 0Simulated
Channel700650600550500450400350300250200150100500
Cou
nts
8,500
8,000
7,500
7,000
6,500
6,000
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Energy [keV]
400 nm
N surface
Ti surface
Ti interface
N, O, Mginterface
22.5
52
N
N
He
Scattered
15
15
Incident
Surface peaks do not change position with incident angle;
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Example: Average Composition
I. Petrov, P. Losbichler, J. E. Greene, W.-D. Münz, T. Hurkmans, and T. Trinh, Thin Solid Films, 302 179 (1997)
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RBS: Oxidation Behavior
TiN/SiO2
Annealed in atmosphere for 12 min at Ta = 600 °C
As-deposited
Experimental spectra and simulated spectra by RUMP
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RBS Summary
N
He
DScattered
15
15
Incident
• Quantitative technique for elemental composition• Requires flat samples; beam size Φ1‐3 mm• Non‐destructive• Detection limit varies from 0.1 to 10‐6, depending on Z
•optimum for heavy elements in/on light matrix, e.g. Ta/Si, Au/C…• Depth information from monolayers to 1 m
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Secondary Ion Mass Spectrometry
SIMS is an analytical technique based on themeasurement of the mass of ions ejected from a solidsurface after the surface has been bombarded withhigh energy (1‐25 keV) primary ions.
Primary Ions Secondary Ions
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Technique Comparison
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Block Diagram of SIMS Technique
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Comparison of Static and Dynamic SIMS
TECHNIQUE DYNAMIC STATICFLUX ~1017 ions/cm2
(minimum dose density)< 1013 ions/cm2
(per experiment)
INFORMATION Elemental Elemental + Molecular
SENSITIVITY < 1 ppm(ppb for some elements)
1 ppm
TYPE OF ANALYSIS Depth ProfileMass Spectrum3D Image Depth Profile
Surface Mass Spectrum2D Surface Ion Image
SAMPLING DEPTH 10 monolayers 2 monolayers
SPATIAL RESOLUTION
Cameca ims 5fProbe mode: 200 nmMicroscope mode: 1 m
PHI TRIFT III0.1 m
SAMPLE DAMAGE Destructive in analyzed area –up to 500 m per area
Minimal
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Magnetic Sector Mass Spectrometer
CAMECA ims 5f
PRIMARY ION COLUMN
SECONDARY ION COLUMN
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Time of Flight Mass Spectrometer
Physical ElectronicsTRIFT III TOF-SIMS
Sample
Cs+ or O2+
Au+
Pre‐Spectrometer Blanker
SED
ContrastDiaphragm
EnergySlit
Post‐SpectrometerBlanker
ESA 1
ESA 2ESA 3
2
21 mveV
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Ion Beam Sputtering
Sputtered species include:• Monoatomic and polyatomic particles of sample material (positive, negative or neutral)• Resputtered primary species (positive, negative or neutral)• Electrons• Photons
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MD Simulation of ion impact
Enhancement of Sputtering Yields due to C60 vs. Ga Bombardment of Ag{111} as Explored by Molecular Dynamics Simulations, Z. Postawa, B. Czerwinski, M. Szewczyk, E. J. Smiley, N. Winograd and B. J. Garrison, Anal. Chem., 75, 4402-4407 (2003).
Animations downloaded from http://galilei.chem.psu.edu/sputtering-animations.html.
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Quantitative Surface Analysis: SIMS
In SIMS, the yield of secondary ions is strongly influenced by the electronic state of the material being analyzed.
Ism = secondary ion current of species m
Ip = primary particle fluxym = sputter yield+ = ionization probability to positive ionsm = factional concentration of m in the layer = transmission of the analysis system
mmpms yII
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Total Ion Sputtering Yield
+
First principles prediction of ion sputter yields is not possible with this technique.
Courtesy of Prof. Rockett
Sputter yield: ratio of number of atoms sputtered to number of impinging ions, typically 5-15
Ion sputter yield: ratio of ionized atoms sputtered to number of impinging ions, 10-6 to 10-2
Ion sputter yield may be influenced by:•Matrix effects•Surface coverage of reactive elements•Background pressure in the sample environment•Orientation of crystallographic axes with respect to the sample surface•Angle of emission of detected secondary ions
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Effect of Primary Beam on Secondary Ion Yields
Oxygen bombardmentWhen sputtering with an oxygen beam, the concentration of oxygen increases in the surface layer and metal-oxygen bonds are present in an oxygen-rich zone. When the bonds break during the bombardment, secondary ion emission process, oxygen becomes negatively charged because of its high electron affinity and the metal is left with the positive charge. Elements in yellow analyzed with oxygen bombardment, positive secondary ions for best sensitivity.
Cesium bombardmentWhen sputtering with a cesium beam, cesium is implanted into the sample surface which reduces the work function allowing moresecondary electrons to be excited over the surface potential barrier. With the increased availability of electrons, there is more negative ion formation. Elements in green analyzed with cesium, negative secondary ions for best sensitivity.
Graphics courtesy of Charles Evans & Associates web sitehttp://www.cea.com
© 2013 University of Illinois Board of Trustees. All rights reserved.
Relative Secondary Ion Yield Comparison
From Storms, et al., Anal. Chem. 49, 2023 (1977).
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Relative Secondary Ion Yield Comparison
From Storms, et al., Anal. Chem. 49, 2023 (1977).
© 2013 University of Illinois Board of Trustees. All rights reserved.
Determination of RSF Using Ion Implants
ii
m
IIRSF
CdIIdCtIRSF
bi
m
LevelProfile:
GaussianProfile:
RSF = Relative Sensitivity FactorIm, Ii = ion intensity (counts/sec) = atom density (atoms/cm3) = implant fluence (atoms/cm2)
mmpms yII
C = # measurement cyclest = analysis time (s/cycle)d = crater depth (cm)Ib = background ion counts
Where:
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Positive and Negative Secondary Ions
0 100 200 300 400 500 600 70010-1
1
10
102
103
104
105
106
Ion implanted P standard
O+2 beam
Si P
Cs+ beam Si P
Cou
nts
/ sec
Depth (nm)0 100 200 300 400 500 600 700
1017
1018
1019
1020
1021
1022
1023 Ion implanted P standard
O+2 beam
Si P
Cs+ beam Si P
Con
cent
ratio
n (a
tom
s/cm
3 )
Depth (nm)
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Definition of Mass Resolution
Graphic courtesy of Charles Evans & Associates web sitehttp://www.cea.com
Mass resolution defined by m/mMass resolution of ~1600 required to resolve 32S from 16O2
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Depth Profile Application with Hydrogen
Detects hydrogen Large dynamic range
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Isotopic Analysis
(b)
(c)
0 50 100 150 200 250 300 350Sputter Time (min.)
0
20
40
60
80
100
Ni Al3NiO, NiAl O , Al O 42 32NiOO
xyge
n Io
n Yi
eld
(% L
inea
r Cou
nts)
16M O
M O18
(a)
AE
S A
tom
ic C
onc
en
tra
tion
(%
)
0
10
20
30
40
50
70
60
Ni Al 600 C: 4 h 18O , 16 h 16O3 2 2R.T. Haasch, A.M. Venezia, and C.M. Loxton. J. Mater.Res., 7, 1341 (1992).
(a) AES composition depth profile(b) SIMS isotopic oxygen diffusion profile expressed as a
percentage of the total oxygen(c) Schematic of layered oxide structure
(a) (b)
(c)
M16OM18O
16O+
18O+O
Al
Ni
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B Depth Profile in Si(001)
SIMS depth profiles through a B modulation-doped Si(001):B film grown by GS-MBE from Si2H6and B2H6 at Ts=600 °C. The incident Si2H6 flux was JSi2H6 = 2.2x1016 cm-2 s-1 while the B flux JB2H6 was varied from 8.4x1013 to 1.2x1016 cm-2 s-1. The deposition time for each layer was constant at 1 h.
G. Glass, H. Kim, P. Desjardins, N. Taylor, T. Spila, Q. Lu, and J. E. Greene. Phys. Rev. B, 61,7628 (2000).
© 2013 University of Illinois Board of Trustees. All rights reserved.
Depth Resolution and Ion Beam Mixing
SIMS depth profiles through a B -doped layers in a Si(001) film grown by GS-MBE from Si2H6 at TS=700 °C. The Si2H6, flux, JSi2H6, was 5X1016 cm-2 s-1 while the B2H6flux, JB2H6 varied from 0.16-7.8X1014 cm-2 s-1. The inset shows the two-dimensional B concentration NB
2D as a function of JB2H6.
Q. Lu, T. R. Bramblett, N.-E. Lee, M.-A. Hasan, T. Karasawa, and J. E. Greene. J. Appl. Phys. 77, 3067 (1995).
© 2013 University of Illinois Board of Trustees. All rights reserved.
Static and Dynamic SIMS
Dynamic SIMS Static SIMS
•Material removal•Elemental analysis•Depth profiling
•Ultra surface analysis•Elemental or molecular analysis•Analysis complete before significant fraction of molecules destroyed
Courtesy Gregory L. Fisher, Physical Electronics
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Extreme Mass Range
0 2000 4000 6000 8000010
110
210
310
410
510
610
710
Tota
l Cou
nts
(9.4
3 am
u bi
n)Integral: 1922 TG_SCAN03_NEGSEC_AU2_22KV_BUNCHED_2NA_400UM_90MIN_CDOUT_CHGCOMP_0-10000AMU.TDC - Ions 400µm 17452848 cts
256015762166
118217731379
788
985394
591
197
Mass (amu)
Tota
l Cou
nts
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Trace AnalysisGaAs Wafer
85.85 85.90 85.95 86.00Mass [m/z]
0
5000
10000
15000
20000
Coun
ts
GaOH
GaNH3m/m = 11,600
Si Wafer
38.94 38.96 38.98 39.00 39.02 39.04Mass [m/z]
010
110
210
310
410
510
610
Coun
ts
K
C3H3
C2HN
No sputtering to remove organics on surface.Large C3H3 peak does not have a tail to lower mass which would obscure C2HN and K.
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InAs/GaAs Quantum Dots
In+ Linescans of Quantum Dots
µm0 0.5 1.0 1.5 2.0
0
5
10
15
20
µm0 0.5 1.0 1.5
0
5
10
15
µm0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0
5
10
15
20
25
Cts: 550893; Max: 36; Scale: 1µm
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GaAs/AlGaAs Depth Profile
Al
Ga
Analysis beam: 15kV Ga+
Sputter Beam: 300V O2+
with oxygen flood
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200 400 600 800 1000Time (Seconds)
010
110
210
310
410
510
Cou
nts
Total_Ion
U
UO
Nd
NdO
200 400 600 800 1000Time (Seconds)
010
110
210
310
410
510
Cou
nts
Total_Ion
UUO
Nd
NdO
Depth Profile Beam Alignment
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TOF‐SIMS Imaging of Patterned Sample
O OO
Br
OS
O OSi
O
OH
O h(nm)
H2O
OS
O OSi
O
OH
OH
Courtesy Josh Ritchey, Audrey Bowen, Ralph Nuzzo and Jeffrey Moore, University of Illinois
400 mS
400 mBr
50 mBr
© 2013 University of Illinois Board of Trustees. All rights reserved.
TOF‐SIMS Ion Images of an Isolated NeuronFirst Images of Vitamin E Distribution in a Cell
Courtesy E.B. Monroe,J.C. Jurchen, S.S. Rubakhin,J.V. Sweedler. University ofIllinois at Urbana-Champaign
© 2013 University of Illinois Board of Trustees. All rights reserved.
TOF‐SIMS Ion Images of Songbird Brain
Selected ion images from the songbird brain. Each ion imageconsists of ~11.5 million pixels within the tissue section and isthe combination of 194 individual 600m×600m ion imagesprepared on the same relative intensity scale. Ion images are(A) phosphate PO3− (m/z 79.0); (B) cholesterol (m/z 385.4);(C) arachidonic acid C20:4 (m/z 303.2); (D) palmitic acidC16:0 (m/z 255.2); (E) palmitoleic acid C16:1 (m/z 253.2); (F)stearic acid C18:0 (m/z 283.3); (G) oleic acid C18:1 (m/z281.2); (H) linoleic acid C18:2 (m/z 279.23); and (I) -linolenicacid C18:3 (m/z 277.2). Scale bars = 2 mm.
Courtesy Kensey R. Amaya, Eric B. Monroe, Jonathan V. Sweedler, David F. Clayton. International Journal of Mass Spectrometry 260, 121 (2007).
© 2013 University of Illinois Board of Trustees. All rights reserved.
Diamond‐Like‐Carbon Friction Testing
wear tracks and scars formed on DLC‐coated disk and ball sides during test in dry oxygen
DLC coated ball
DLC coated disk
Oxygen Carbon C + O Overlay
Courtesy O.L. Eryilmaz and A. ErdemirEnergy Systems Division, Argonne National Laboratory Argonne, IL 60439 USA
© 2013 University of Illinois Board of Trustees. All rights reserved.
3‐D TOF‐SIMS imaging of DLCWear track from hydrogenated DLC tested in dry nitrogenCourtesy O.L. Eryilmaz and A. ErdemirEnergy Systems Division, Argonne National Laboratory Argonne, IL 60439 USA
© 2013 University of Illinois Board of Trustees. All rights reserved.
3‐D TOF‐SIMS Movies of DLC
H CH C2H C2H2O
NFC6 H2 Environment TOF-SIMS ImagesCourtesy O.L. Eryilmaz and A. ErdemirEnergy Systems Division, Argonne National Laboratory Argonne, IL 60439 USA
© 2013 University of Illinois Board of Trustees. All rights reserved.
SIMS Summary
Probe/Detected Species InformationSurface Mass Spectrum2D Surface Ion ImageElemental Depth Profiling3D Image Depth Profiling
Elements DetectableH and above
Sensitivityppb - atomic %
Analysis Diameter/Sampling Depth~1 m - several mm/0.5 - 1nm
© 2013 University of Illinois Board of Trustees. All rights reserved.
Acknowledgments