Transcript
University of Illinois at Urbana-Champaign | Materials Research Laboratory
Advanced Materials Characterization Workshop June 3 and 4, 2013
Rutherford Backscattering & Secondary Ion Mass Spectrometery Timothy P. Spila, Ph.D. Frederick Seitz Materials Research Laboratory University 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 the back-scattered ions can be measured to give information on sample composition as a function of depth. © 2013 University of Illinois Board of Trustees. All rights reserved.
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.
© 2013 University of Illinois Board of Trustees. All rights reserved.
Rutherford Backscattering Spectrometry 2 MeV Van de Graaff accelerator
beam size Φ1-3 mm flat sample can be rotated
© 2013 University of Illinois Board of Trustees. All rights reserved.
energy loss per cm log(dE/dx)
Primary Beam Energy
1 keV
1 MeV
(log E)
1 keV
1 MeV
thin film projected on to a plane: atoms/cm2
(Nt)[at/cm2] = N[at/cm3] * t[cm] Figure after W.‐K. Chu, J. W. Mayer, and M.‐A. Nicolet, Backscattering Spectrometry (Academic Press, New York, 1978). © 2013 University of Illinois Board of Trustees. All rights reserved.
Elastic Two‐Body Collision Elastic Scattering M1vo2 = M1v12 + M2v22 M1vo = M1v1 + M2v2
E1 = KEo M t2 M i2 sin 2 M i cos K M M i t
2
Kinematic factor: K
1.0
M14
0.8 0.6
He
0.4
4
= 150
o
0.2 0.0 0
50
100
150
200
Target mass (amu) © 2013 University of Illinois Board of Trustees. All rights reserved.
Rutherford Scattering Cross Section
Coulomb interaction between the nuclei: exact expression -> quantitative method
Z1Z 2 R ( E , ) 4E
2
4 Z2 1 M sin ( 2 ) 2( M 2 ) E
© 2013 University of Illinois Board of Trustees. All rights reserved.
2
energy loss per cm log(dE/dx)
Electron Stopping
1 keV
1 MeV
(log E)
Figure after W.‐K. Chu, J. W. Mayer, and M.‐A. Nicolet, Backscattering Spectrometry (Academic Press, New York, 1978). © 2013 University of Illinois Board of Trustees. All rights reserved.
RBS – Simulated Spectra hypothetical alloy Au0.2In0.2Ti0.2Al0.2O0.2/C Element (Z,M): O(8,16), Al(13,27), Ti(22,48), In(49,115), Au(79,197) 2
R ( E , )
Z2 E
Kinematic factor: K
1.0
1200
8000
10 ML
Au
C
0.8
100 ML
Au
0.6 4
He
0.4
In
o
= 150
In
0.2 0.0 0
50
100
150
200
O
Target mass (amu)
Al
Ti C
O
Al
Ti
16000
1000 ML
In
20000
50000
4000 ML
Au
C
O
Al
Ti © 2013 University of Illinois Board of Trustees. All rights reserved.
10000 ML
SIMNRA Simulation Program for RBS and ERD
© 2013 University of Illinois Board of Trustees. All rights reserved.
Thickness Effects TiN/MgO Energy [keV] 100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
11,000
Series 0 Series 1
300 nm
10,500 10,000 9,500 9,000
Scattered
1500
11,500
D
8,500
N
8,000 7,500
N surface
Counts
7,000 6,500
15
6,000
15
5,500 5,000 4,500
Ti surface
4,000 3,500
Incident
3,000
Ti interface
N, O, Mg interface
2,500 2,000 1,500 1,000
He
500 0 0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
Channel
Energy [keV] Energy [keV] 100
200
300
400
500
600
700
800
900
100 1000
1100
1200
1300
1400
14,000
Series 0 Simulated
14,000
12,000 11,000
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500 Series 0 Simulated
600 nm
13,000
400 nm
13,000
200
1500
12,000 11,000 10,000
10,000
9,000
N surface
8,000
Counts
Counts
9,000
7,000
8,000 7,000
N surface
6,000 6,000
5,000 5,000
Ti surface
4,000
N, O, Mg interface
3,000 2,000 1,000
Ti interface
50
100
150
200
250
300
350
400
Channel
450
500
550
600
650
3,000
Ti interface
2,000 1,000
0
0 0
Ti surface
4,000
N, O, Mg interface
700
0
50
100
150
200
250
300
350
400
Channel
© 2013 University of Illinois Board of Trustees. All rights reserved.
450
500
550
600
650
700
Incident Angle Effects TiN/MgO
Scattered N
15
52
15
Incident
22.5
He
N Energy [keV]
Energy [keV] 100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
100
1500
13,000
400 nm
12,000 11,000
8,000
Ti surface
7,500
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500 Series 0 Simulated
Ti surface
7,000 6,500 6,000
10,000
5,500
9,000
N surface
8,000
Counts
Counts
300
400 nm
8,500
Series 0 Simulated
14,000
200
7,000
5,000 4,500 4,000
N surface
3,500
6,000
3,000
5,000
2,500
N, O, Mg interface
4,000
2,000
N, O, Mg interface
3,000 2,000 1,000
1,000 500
0
0 0
50
100
150
200
250
300
350
400
450
500
550
600
650
Ti interface
1,500
Ti interface 700
0
50
100
150
Channel
200
250
300
350
400
450
Channel
Surface peaks do not change position with incident angle; © 2013 University of Illinois Board of Trustees. All rights reserved.
500
550
600
650
700
Example: Average Composition
I. Petrov, P. Losbichler, J. E. Greene, W.-D. Münz, T. Hurkmans, and T. Trinh, Thin Solid Films, 302 179 (1997) © 2013 University of Illinois Board of Trustees. All rights reserved.
RBS: Oxidation Behavior
TiN/SiO2 As-deposited Experimental spectra and simulated spectra by RUMP
Annealed in atmosphere for 12 min at Ta = 600 °C © 2013 University of Illinois Board of Trustees. All rights reserved.
RBS Summary Scattered
D
15
N
15
Incident He
• 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 © 2013 University of Illinois Board of Trustees. All rights reserved.
Secondary Ion Mass Spectrometry
SIMS is an analytical technique based on the measurement of the mass of ions ejected from a solid surface after the surface has been bombarded with high energy (1‐25 keV) primary ions. Primary Ions
Secondary Ions
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Technique Comparison
© 2013 University of Illinois Board of Trustees. All rights reserved.
Block Diagram of SIMS Technique
© 2013 University of Illinois Board of Trustees. All rights reserved.
Comparison of Static and Dynamic SIMS TECHNIQUE
DYNAMIC
STATIC
FLUX
~1017 ions/cm2
< 1013 ions/cm2
(minimum dose density)
(per experiment)
INFORMATION
Elemental
Elemental + Molecular
SENSITIVITY
< 1 ppm
1 ppm
(ppb for some elements)
TYPE OF ANALYSIS
Depth Profile Mass Spectrum 3D Image Depth Profile
Surface Mass Spectrum 2D Surface Ion Image
SAMPLING DEPTH
10 monolayers
2 monolayers
SPATIAL RESOLUTION
Cameca ims 5f Probe mode: 200 nm Microscope mode: 1 m
PHI TRIFT III 0.1 m
SAMPLE DAMAGE
Destructive in analyzed area – up to 500 m per area
Minimal
© 2013 University of Illinois Board of Trustees. All rights reserved.
Magnetic Sector Mass Spectrometer CAMECA ims 5f
SECONDARY ION COLUMN
PRIMARY ION COLUMN
© 2013 University of Illinois Board of Trustees. All rights reserved.
Time of Flight Mass Spectrometer Physical Electronics TRIFT III TOF-SIMS
ESA 3
ESA 2
Cs+ or O2+
Sample
SED
Pre‐Spectrometer Blanker
Au+
Energy Slit
Post‐ Spectrometer Blanker
Contrast Diaphragm
ESA 1
1 2 eV mv 2
© 2013 University of Illinois Board of Trustees. All rights reserved.
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 © 2013 University of Illinois Board of Trustees. All rights reserved.
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/sputteringanimations.html.
© 2013 University of Illinois Board of Trustees. All rights reserved.
Quantitative Surface Analysis: SIMS
I I p ym m m s
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 flux ym = sputter yield + = ionization probability to positive ions m = factional concentration of m in the layer = transmission of the analysis system
© 2013 University of Illinois Board of Trustees. All rights reserved.
Total Ion Sputtering Yield 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
+
First principles prediction of ion sputter yields is not possible with this technique. © 2013 University of Illinois Board of Trustees. All rights reserved.
Courtesy of Prof. Rockett
Effect of Primary Beam on Secondary Ion Yields
Graphics courtesy of Charles Evans & Associates web site http://www.cea.com
Oxygen bombardment When 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 bombardment When sputtering with a cesium beam, cesium is implanted into the sample surface which reduces the work function allowing more secondary 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. © 2013 University of Illinois Board of Trustees. All rights reserved.
Relative Secondary Ion Yield Comparison
© 2013 University of Illinois Board of Trustees. All rights reserved.
From Storms, et al., Anal. Chem. 49, 2023 (1977).
Relative Secondary Ion Yield Comparison
© 2013 University of Illinois Board of Trustees. All rights reserved.
From Storms, et al., Anal. Chem. 49, 2023 (1977).
Determination of RSF Using Ion Implants
I I p ym m m s
Level Profile:
Im i RSF Ii
Gaussian Profile:
I mCt RSF d I i dI bC
Where:
RSF = Relative Sensitivity Factor Im, Ii = ion intensity (counts/sec) = atom density (atoms/cm3) = implant fluence (atoms/cm2)
C = # measurement cycles t = analysis time (s/cycle) d = crater depth (cm) Ib = background ion counts
© 2013 University of Illinois Board of Trustees. All rights reserved.
Positive and Negative Secondary Ions 10
6
Ion implanted P standard 10
5
10
4
10
3
10
2
10 1
O2 beam
10
3
Si P + Cs beam Si P
+
22
Concentration (atoms/cm )
Counts / sec
+
O2 beam
Ion implanted P standard
23
10
Si P + Cs beam Si P
21
10
20
10
19
10
18
10
17
10
-1
10
0
100
200
300
400
500
600
700
0
100
200
Depth (nm) © 2013 University of Illinois Board of Trustees. All rights reserved.
300
400
500
Depth (nm)
600
700
Definition of Mass Resolution Mass resolution defined by m/m Mass resolution of ~1600 required to resolve 32S from 16O2
Graphic courtesy of Charles Evans & Associates web site http://www.cea.com © 2013 University of Illinois Board of Trustees. All rights reserved.
Depth Profile Application with Hydrogen
Detects hydrogen
Large dynamic range © 2013 University of Illinois Board of Trustees. All rights reserved.
Isotopic Analysis R.T. Haasch, A.M. Venezia, and C.M. Loxton. J. Mater.Res., 7, 1341 (1992).
Ni 3Al 600 C: 4 h 18O2, 16 h 16O2 AES Atomic Concentration (%)
(a)
(b)
70 60
Ni
30
Al
20 10
16O+
80
50 40
100
(b) Oxygen Ion Yield (% Linear Counts)
(a)
60 40
18O+
20
O
0
0
0
50
100
(c)
(a) (b) (c)
AES composition depth profile SIMS isotopic oxygen diffusion profile expressed as a percentage of the total oxygen Schematic of layered oxide structure
(c)
150
200
250
300
Sputter Time (min.) M16O M18O
NiO
NiO, NiAl 2O4 , Al2 O3
M18O © 2013 University of Illinois Board of Trustees. All rights reserved.
M16O
Ni 3 Al
350
B Depth Profile in Si(001) SIMS depth profiles through a B modulation-doped Si(001):B film grown by GS-MBE from Si2H6 and 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 B2H6 flux, JB2H6 varied from 0.16-7.8X1014 cm-2 s-1. The inset shows the two-dimensional B concentration NB2D 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 © 2013 University of Illinois Board of Trustees. All rights reserved.
Extreme Mass Range Integral: 1922
TG_SCAN03_NEGSEC_AU2_22KV_BUNCHED_2NA_400UM_90MIN_CDOUT_CHGCOMP_0-10000AMU.TDC - Ions 400µm 17452848 cts
107 197
106
591 394 985
Total Counts (9.43 amu bin)
Total Counts
788
105
1379
1773
1182
2166 1576
2560
104
103
102
101
100
0
2000
4000
6000
Mass (amu) © 2013 University of Illinois Board of Trustees. All rights reserved.
8000
Trace Analysis 10 6
GaAs Wafer GaOH
20000
C3H3
10 5
m/m = 11,600
10 4
GaNH3
K
Counts
Counts
15000
Si Wafer
C2HN
10 3
10000 10 2
5000
0
10 1
85.85
85.90
10 0 38.94
38.98 39.00 39.02 39.04 Mass [m/z] No sputtering to remove organics on surface. Large C3H3 peak does not have a tail to lower mass which would obscure C2HN and K. © 2013 University of Illinois Board of Trustees. All rights reserved.
85.95 Mass [m/z]
86.00
38.96
InAs/GaAs Quantum Dots In+ Linescans of Quantum Dots
15
10
5
0
0
Cts: 550893; Max: 36; Scale: 1µm
0.5
1.0 µm
1.5
25 20
20
15
15
10
10
5
5
0
0
0.5
1.0
µm
1.5
2.0
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 µm
© 2013 University of Illinois Board of Trustees. All rights reserved.
GaAs/AlGaAs Depth Profile
Al
Analysis beam: 15kV Ga+ Sputter Beam: 300V O2+ with oxygen flood
Ga
© 2013 University of Illinois Board of Trustees. All rights reserved.
Depth Profile Beam Alignment
Counts
Total_Ion
105
UO
104
U
103 NdO
102 101
Counts
100
Nd
200
400
600 Time (Seconds)
800
1000
105
Total_Ion
104
UO U
103 NdO
102
Nd
101 100 200 400 © 2013 University of Illinois Board of Trustees. All rights reserved.
600 Time (Seconds)
800
1000
TOF‐SIMS Imaging of Patterned Sample O O
Br O
S
O
O S
O
Si O
h(nm)
OH
H2O
O Si O OH
O
Br 400 m
H O S O O
Br 400 m
50 m
Courtesy Josh Ritchey, Audrey Bowen, Ralph Nuzzo and Jeffrey Moore, University of Illinois © 2013 University of Illinois Board of Trustees. All rights reserved.
TOF‐SIMS Ion Images of an Isolated Neuron First Images of Vitamin E Distribution in a Cell
Courtesy E.B. Monroe, J.C. Jurchen, S.S. Rubakhin, J.V. Sweedler. University of Illinois 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 image consists of ~11.5 million pixels within the tissue section and is the combination of 194 individual 600m×600m ion images prepared 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 acid C16:0 (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/z 281.2); (H) linoleic acid C18:2 (m/z 279.23); and (I) -linolenic acid 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
DLC coated ball
DLC coated disk
Oxygen
Carbon
C+O Overlay
wear tracks and scars formed on DLC‐coated disk and ball sides during test in dry oxygen
Courtesy O.L. Eryilmaz and A. Erdemir Energy 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 DLC Wear track from hydrogenated DLC tested in dry nitrogen Courtesy O.L. Eryilmaz and A. Erdemir Energy 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 NFC6 H2 Environment TOF-SIMS Images Courtesy O.L. Eryilmaz and A. Erdemir Energy Systems Division, Argonne National Laboratory Argonne, IL 60439 USA
H
CH
C2H
C2H2
© 2013 University of Illinois Board of Trustees. All rights reserved.
O
SIMS Summary Probe/Detected Species
Information Surface Mass Spectrum 2D Surface Ion Image Elemental Depth Profiling 3D Image Depth Profiling Elements Detectable H and above Sensitivity ppb - atomic % Analysis Diameter/Sampling Depth ~1 m - several mm/0.5 - 1nm
© 2013 University of Illinois Board of Trustees. All rights reserved.
Acknowledgments
© 2013 University of Illinois Board of Trustees. All rights reserved.
