1 medium energy ion scattering and elastic recoil detection analysis for processes in thin films and...
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Medium energy ion scattering and elastic recoil detection analysis for processes in
thin films and monolayers
Lyudmila V. Goncharova, Sergey Dedyulin, Mitch Brocklebank
Department of Physics and Astronomy, Western University ,
London, Ontario, Canada
Collaborators: P. J. Simpson (UWO), J. Botton (McMaster U.), D. Londheer (NRC)
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Duoplasmatron Source
Sputter Source
Injector MagnetTandetron Accelerator
High Energy Magnet
RBS Chamber
ERD Chamber
MEIS Chamber
Implant Chamber
Group III,V Molecular BeamEpitaxy System
Group IV Molecular BeamEpitaxy System
2
1.7 MeV Tandetron Accelerator Facility at UWO
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2D MEIS Data
2
21
122
122 cossin
MM
MMMEE od
•mass (isotope) specific•quantitative (2% accuracy)•depth sensitive (at the sub-nm scale)
Energy distributions:
77 84 910
500
1000
1500
O(buried)
Zr(buried)
O(surf)
Ge(buried)Si
(surf)
Yie
ld
Energy [keV]
SiO2/ Si /ZrO
2/GeO
x/Ge(001)
Experiment Total Spc
100keV H+, SiO2/poly-Si/ZrO2/Ge(100)
H+ E
nerg
y [k
eV]
Angle 115 120 125 130 135 140
H+ Y
ield
Angle [degree]
Energy distribution for one angle
Angular distribution for one element
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Outline
• Motivation
• Medium Energy Ion Scattering (MEIS) - Nucleation and growth in Si and Ge quantum systems
• Medium Energy Elastic Recoil Detection (ME-ERD) - H-terminated Si(001)
- H in HfSiOx ultra-thin films /Si(001)
• Conclusions and future directions
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For the Age of Photonics…
• Continued developments in – miniaturization, – speed and complexity
• Wiring bottleneck• Need to merge electronics and photonics• III-V compounds dominate optoelectronics• Hybrid technologies are being used• OEICs and OICs incorporating Si/Ge detectors,
modulators and waveguides now functional
5
D.J. Paul, Semicond. Sci. Tech. 19, R75 (2009)
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Overcoming the indirect band gap
• Alloying Ge with Si and/or C• Stress• Brillouin zone folding
• Rare earth and transition metal impurity centres
• Quantum confinement– Wells (1-D)– Wires (2-D)– Dots (3-D)
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Band gap engineering
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Experimental Approach
Ion beam implantation
7
Tx, N2
*Stopping and Range of Ions in Matter, www.srim.org/
SRIM*
Photoluminescence (PL)h
h2
Life-time decay
X-ray Photoemission Spec.
Rutherford Backscat. (RBS)Elastic Recoil Detection (ERDA)Raman
Rutherford Backscat. (RBS)Elastic Recoil Detection (ERDA)Raman
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Growth and Analysis of Si QD• RT Implantation Si- or Ge+ 90keV 5x1016 -1x1017ions/cm2
• 120min @11000C (Si) or 9000C (Ge)
in furnace, 60 min @5000C in N2/H2 gas
• Early stage of formation governed
by diffusion
• Eventually Ostwald ripening
)(4 solSiSi CCrNDt
C
Link between defects in the SiO2 and formation of Si-QDs*
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Ge QDPhotoluminescense in Ge quantum systems
• Ge QD PL has two components:
blue-green PL at ~2 eV (590 nm) independent of NC size
near infrared PL size dependent, compatible with a QC effect• Larger exciton radius (24 nm) compared with Si (~4nm) causes
larger confinement effect in Ge QD• Very challenging to fabricate a defect-free stable Ge QD!!!
N.L. Rowell, et al., JES 156, H913 (2009)
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Ion beam implantation
Tx, N2
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Ge in Al2O3(0001): crystallization and ordering
E.G. Barbagiovanni, et al., NIMB 272 (2012) 74–77
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XPS
• Shift of Ge peak towards the surface (RBS)
• GeOx peaks in XPS Ge loss via GeO desorption
11
Ar sputtering prior to XPS analysis: Ge layer is 3-5nm deep
Al2O3(0001)
GexO
disordered Al2O3
Tx>1100oC
N2 Al2O3(0001)
Ge-QD
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Cross-sectional TEM micrographs
• Contrast arising from stress fields and end of range implantation damage
• Moiré fringes become visible from the overlap of the crystal planes of Ge QD and the sapphire matrix
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Ge QD in Al2O3(0001): MEIS vs HRTEM
• Slow diffusion rate of the alumina matrix atoms at < Tmelt
• Ge blocking minimum can be related to the stereographic projection of the sapphire crystal and corresponds to the [111] scattering plane:
(1104) Al2O3 // (111)Ge and [211] Al2O3 // [112] Ge
100 105 110 115 120 1250.0
0.7
1.4
2.1
In
tegr
ated
Yie
ld
Scattering Angle [degrees]
Ge
Al
[111]
I.D. Sharp, Q. Xu, D.O.Y, et al., JAP 100 (2006) 114317
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Outline
• Motivation
• Medium Energy Ion Scattering (MEIS) - Nucleation and growth in SI and Ge quantum systems
• Medium Energy Elastic Recoil Detection (ME-ERD) - H-terminated Si(001)
- H in HfSiOx ultra-thin films /Si(001)
• Conclusions and future directions
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Quantification in MEIS
• Scattering potential• Cross section• Neutralization
RBS vs MEIS
Normalized ion yield:
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Missing element from the picture… hydrogen!
Heavy Elements by MEIS or RBS
Light Elements by Elastic Recoil Detection
Detector
Light elements (He+ or H+)
Detector
He+
H+, He+ “Classical” ERDIncident energy = 1.6MeV He+
Incident angle = 75o
Recoil Angle = 30o
Al-mylar (range foil)
200 250 300 350 400 450 500 550 6000
50
100
150
200
Yie
ld
Energy [keV]
Kapton 1034 1051 1085 1091 1097
~150nm SiONH/Si(001)
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TEA detector for negative ions
Crucial points for detecting H ion recoils directly are:
• To increase the recoil cross-section
• To reduce (to suppress) the background originating mainly from elastically scattered incident ions
• To reduce recoil energy
V-
V+
MEIS
V-V+
ME-ERD
Only charged particles are detected by TEA
use incident beam ions without negative ion fractions and detect negative H- recoils
X+ H+,H, H-
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Selection of Incident Ions
• Potential candidates: B, N, Ne, Na, Mg, Al, Si, P…
• Limitations:
- possibility to produce these ions beam
- high beam current
- only H- are detected (fraction can
be small)
W.N. Lennard, et al. NIMB 179 (1981) 413
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0 200 400 600 8000
100
200
300
400
500
Incident beam: 500 keV Si
TEA center: 75
Yie
ld
Channel (Angle)
H-Si(001) fitting area background fit
ME-ERD for H-Si(001)
Incident beam: 500keV Si+
Incident angle = 45o
Recoil Angle = 75o (TEA centre)
Dose = 0.5CSi+
H-
60 70 80 900
5
10
15
20
Re
coil
En
erg
y [k
eV
]
Detector Angle [deg]
SiH
60 65 70 75 80 85 900
500
1000
1500
2000
2500
3000
Nor
mal
ized
Yie
ld
Detector Angle [deg]
Recoil E (3.0 keV) Recoil E (4.0 keV) Recoil E (5.0 keV)
H
Si
Although the fraction of Si- ions is small, it is not negligible!
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60 70 80 900
5
10
15
20
R
ecoi
l Ene
rgy
[keV
]
Detector Angle [deg]
SiH
20
ME-ERD for H-Si(001)
65 70 75 80 850
80
160
H-Si(001) 3keV H-Si(001) 4keV
Yie
ld
Detector Angle [deg]
H- Si(001) vs H-Si(111)
H- Si(001): assuming dihydride model 1.38x1015 /cm2
Sensitivity to H: 8x1013 H/cm2
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H- Yield as a function of Si+ dose
• Irradiated area need to be refreshed!
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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00
100
200
300
400
500
600
700
800
500keV Si+ H-Si(001)E(H)= 4keV
Experimental Fit
Rec
oile
d H
- Y
ield
[cou
nts/
0.1 C
]
Si+ Dose [I, C]
YH(I) =984 exp (-I/k)
k=0.27 C
Without shifting irradiation area
• YH(I=0) = 984 ~ 30% of H is lost after 0.1C• Data shown below is without correction of H loss from
the surface
Si+
H-
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60 70 80 900
5
10
15
20
R
ecoi
l Ene
rgy
[keV
]
Detector Angle [deg]
SiH
22
ME-ERD for H-Si(001)
65 70 75 80 850
80
160
H-Si(001) 3keV H-Si(001) 4keV
Yie
ld
Detector Angle [deg]
H- Si(001) vs H-Si(111)
H- Si(001): assuming dihydride model 1.38x1015 /cm2
Estimate of sensitivity to H: 8×1013 H/cm2
Extrapolated sensitivity to H: 1×1013 H/cm2
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Angular dependence
• observe angular dependence of H- fraction• No H peaks at angles above 80o
• Low sensitivity at angles < 60o
23
65 70 75 80 85 900
10
20
30
40
50
60
70
H+ F
ract
ion
(%)
Recoil Angle [deg]
104.3 keV Ne+, 1x1 H - Si(111) E
H=5 keV [1]
J.B. Marion, F.C. Young, NRA Tables, 1968.K. Mitsuhara et al., NIMB 276 (2012) 56-67
60 65 70 75 80 850
1000
2000
3000
500 keV Si+
Yie
ld
Recoil Angle (deg.)
EH=2keV
EH=3keV
EH=4keV
EH=5keV
EH=6keV
EH=7keV
Step dose: 0.5 uC
60 65 70 75 80 850
1
2
3
4
5
6
7
8
9
Rel
ativ
e H
- fr
actio
n (%
)
Recoil angle [deg]
500 keV Si+, H-Si(001)E
H=2-7keV
Marion-Young
Best conditions at EH=2-5keV and angle = 70-80o
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ME-ERD for Hf silicate films
Sample Tdep, C #cycles Thickness, nm In-situ RTA
1367 200 16 3.6
1351 300 19 3.6 UHV, 800oC, 30 sec
1355 350 21 3.4
1376 350 60 16
65 70 75 80 850
100
200
300
Y
ield
Angle [degrees]
Tx=200oC
Tx=300oC
Tx=350oC
Si+
H-
Incident beam: 500keV Si+
Incident angle = 45o
Dose = 0.5C
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Summary: Towards “Complete ME-IBA”
We were able to detect hydrogen using ME-ERD using Si(N) incident beams with no modification in TEA
Medium Energy Elastic Recoil Spectroscopy with incident Si, N ions gives complimentary information on hydrogen content
• Hi-Si(001): we observe angular dependence of H- fraction
• The H- fraction is expected to increase with decreasing energy of the recoils (incident energy)
– Damage effects are significant surface needs to be refreshed under the beam
– Uniform lateral distribution is assumed
– Accurate background fit is necessary to get quantitative fitting
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Thank you!Thank you!