x ray

2.  Introduction
 Data Processing List according to each Analysis
 Ultraviolet Photoelectron Spectroscopy
 XPS Applications in Semiconductor Devices
• MIS Contacts
• MOSCAP structures
• MoS2 and MoS2-TiO2 structures
OUTLINE
7/12/2015 2IIT Bombay

3. Introduction
X-ray Photoelectron Spectroscopy (XPS) is a
surface-sensitive spectroscopic technique that is
used to measure :
 elemental composition
 empirical formula
 chemical state and electronic state of the elements that
exist within a material
The Versa Probe is PHI’s second
generation XPS based Multi-
technique system. The unique
strength of the system is its ability
to image and analyze features as
small as 10μm in diameter.
Model: PHI 5000 Versa Probe-II7/12/2015 3IIT Bombay

4. Data Processing List according to each Analysis
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5.  Introduction
 Data Processing List according to each Analysis
 Ultraviolet Photoelectron Spectroscopy
 XPS Applications in Semiconductor Devices
• MIS Contacts
• MOSCAP structures
• MoS2 and MoS2-TiO2 structures
OUTLINE
7/12/2015 5IIT Bombay

6. Ultraviolet Photoelectron Spectroscopy (UPS)
 If ultraviolet photons (rather than X-rays) are used, the
technique is called Ultraviolet Photoelectron Spectroscopy
(UPS).
 Other than the photon source, instrumentation is
identical to that of XPS.
 The optional Ultraviolet photon source provides low
energy photons for Valence Band and Fermi edge
measurements.
 Helium gas can be used to generate single and doubly
ionized UV photon sources.
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7.  Introduction
 Data Processing List according to each Analysis
 Ultraviolet Photoelectron Spectroscopy
 XPS Applications in Semiconductor Devices
• MIS Contacts
• MOSCAP structures
• MoS2 and MoS2-TiO2 structures
• Al2O3 thin film
• Nickel Silicide
OUTLINE
7/12/2015 7IIT Bombay

8. XPS Applications in Semiconductor Devices
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 XPS was used for the study of Metal Insulator Semiconductor (MIS)
contacts fabricated on low-doped bulk n-Ge substrates
n-Ge
Yb
TiO2
Au
• Depth Profile of the structure
gives a plot of Atomic
Concentration vs. Sputter
Time
• Presence of TiO2 is detected
from the plot
TiO2

9. Ti2p scan after 35, 37, 39 min sputter
times
After 35 min sputter
(energy interval on x axis
is 0.25 eV)
After 37 min sputter
(energy interval on x axis
is 0.1 eV)
After 35 min sputter
(energy interval on x axis
is 0.1 eV)
• Similar spectra seen at 3 different points in the depth profile
• Spectral deconvolution shown on next slide

10. 3400
3500
3600
3700
3800
3900
4000
4100
4200
450455460465470475
Spectrum Ti(II)2p3/2 (454.41 eV)
Ti(IV) 2p3/2 Ti(II)2p1/2
Ti(III) 2p 1/2 Ti(IV) 2p1/2 (463.13)
Ti(III) 2p3/2 (458.27 eV)
Energy (eV)
Counts
• Different oxidation states of Ti
• Presence of Ti(II), Ti(III) and Ti(IV) from this it is
concluded that it has oxygen deficient phase
• The intensity of O1s peak at 532eV increases
suggests oxygen vacancies thus, oxygen deficient
TiO2 has been formed at the interface.
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
528530532534536538
Binding Energy (eV)
O1s bare TiO2
0
0.2
0.4
0.6
0.8
1
1.2
528530532534536538
Binding Energy (eV)
O1s interface TiO2
0
0.2
0.4
0.6
0.8
1
1.2
45455460465470
Binding Energy (eV)
Ti2p bare TiO2

11.  Introduction
 Basic Theory of XPS
 XPS as a Surface Analysis Technique
 Data Processing List according to each Analysis
 Ultraviolet Photoelectron Spectroscopy
 XPS Applications in Semiconductor Devices
• MIS Contacts
• MOSCAP structures
• MoS2 and MoS2-TiO2 structures
OUTLINE
7/12/2015 11IIT Bombay

12. Intensity(a.u.)
O1s Al2
O3
526 528 530 532 534 536
O1s HfO2
Binding Energy (eV)
Intensity(a.u.)Intensity(a.u.)
O1s HfAlO
(Al=11.6%)
0
5
10
15
20
25
30
35
HfAlO
(Al:Hf=1:2)
HfAlO
(Al:Hf=2:1)
HfAlO
(Al:Hf=3:3)
%Al
Al2
O3
HfO2
Recipe
Used
529.8
530.0
530.2
530.4
530.6
530.8
531.0
HfO2
HfAlO(Al:Hf=1:2)
HfAlO(Al:Hf=3:3)
O1speakposition(eV)
Al2
O3
HfAlO(Al:Hf=2:1)
Figure shows O1s peak position as
function of Al%
Al% determination using XPS
XPS Applications in Semiconductor Devices (contd.)
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 XPS was used for the study of MOSCAP structures fabricated on
Ge substrates
HfO2/HfAlO/Al2O3

13. Shift in Hf4f peak after PDA of
HfO2/GeO2/Ge indicating
formation of GeOHf
Effect of Post Deposition Anneal (PDA) on HfO2
0 5 10 15 20
0.0
0.2
0.4
0.6
0.8
1.0
Intensity(A.U.)
Time (min)
Hf4f without PDA
Hf4f with PDA
O1s without PDA
O1s with PDA
Ge3d without PDA
Ge3d with PDA
HfO2 Ge
substrate
13 14 15 16 17 18 19 20 21 22 23
0.31eV
Intensity(a.u.) Binding Energy (eV)
Hf4f withPDA
Hf4f without PDA
Depth profile of HfO2/GeO2/Ge
indicating GeO2 growth and
formation of GeOHf,
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XPS Applications in Semiconductor Devices (contd.)

14.  Introduction
 Basic Theory of XPS
 XPS as a Surface Analysis Technique
 Data Processing List according to each Analysis
 Ultraviolet Photoelectron Spectroscopy
 XPS Applications in Semiconductor Devices
• MIS Contacts
• MOSCAP structures
• MoS2 and MoS2-TiO2 structures
OUTLINE
7/12/2015 14IIT Bombay

15. Mo-3d and S-2p core level shifts to higher binding energy from MoS2 to
TiO2–MoS2 confirms charge transfer at the interface.
XPS Applications in Semiconductor Devices (contd.)
 XPS was used to study MoS2 and TiO2-MoS2 structures

16. 10 5 0 -5
0
2M
4M
6M
8M
Counts(a.u.)
Binding Energy(eV)
MoS2
TiO2
-MoS2
12.0 11.6 11.2 10.8
11.9
MoS2
TiO2
-MoS2
11.6
He I-UPS measurements of TiO2–MoS2 and MoS2 show a reduction in work-
function (0.3 eV) using TiO2 as an interlayer
XPS Applications in Semiconductor Devices (contd.)
 UPS was used to study MoS2 and TiO2-MoS2 structures

17. -2 0 2 4 6 8 10 12 14 16 18 20 22
0
20
40
60
80
100
Atomicconcentration(%)
Sputter time (min)
Al2p
si2p
c1s
N1s
O1s
-2 0 2 4 6 8 10 12 14 16
0
20
40
60
80
100
Atomicpercentage(%)
Sputter time (min)
Al2p
si2p
c1s
N1s
O1s
Figure 1(a) and 1(b) shows atomic concentration of spray coated Al2O3
film after furnace annealing of 400 o C and 850o C respectiely in O2
ambient
Depth profile of Al2O3 thin film by XPS

18. XPS Analysis of Al2O3 thin film
Chemical and interface properties of Al2O3 film is studied with the help of
X-ray photoelectron spectroscopy (XPS) depth profile analysis and the results
are shown in the figure .
XPS analysis shows presence of SiOx interfacial layer after furnace
annealing and the thickness of SiOx interfacial layer increases as the
annealing temperature increases. Si and O are interdiffused which indicates
presences of SiOx. The Length of inter diffused region is more for high temp
anneal.
The carbon and nitrogen content is almost zero throughout the sample.
The carbon signal at the surface is attributed to unavoidable inclusion of
carbon from XPS instrument.
The Atomic percentage of chemical components present in the film
indicates that the Al2O3 film is almost stoichiometric in nature

19. NiSi on Si
• NiSi is formed by
deposition of Ni on Si and
by thermal annealing at
the temperature of 500
0C, for 60 sec.
• The formation of NiSi can
be realised by the metal
diffusion through
semiconductor at that
elevated temperature
Ni
Si
Nickel silicide
Si

20. The depth profile of the nickel silicide(NiSi) is
shown in the figure.
The sputter rate was used to be 2.5 nm/ cycle
The inset shows the Ni/Si ratio of the thin film.
Which indicates that Ni/Si ~ 1 till 27 nm. This
observation indicates that the NiSi film is uniform
till 27 nm.
The thickness was confirmed by cross-sectional
SEM.
Ref:
S. Roy, K. Midya, S. P. Duttagupta, and D.
Ramakrishnan; Nano-scale NiSi and n-type silicon
based Schottky Barrier diode as a near infra-red
detector for room temperature operation; J.
Appl. Phys. 116, 124507 (2014).
Depth Profile of NiSi/n-Si

21. Reduction of Langmuir-Blodgett Graphene Oxide monolayer sheets
• Thickness of as-transferred GO
monolayer sheets obtained by AFM
height profile was found to be ~1 nm
 In the de-convoluted C-1s core level spectra
C-1s core level
 Peaks at 284.5 eV and 285.4 eV are, respectively, assigned to sp2-C (graphitic) and the damaged
alternant hydrocarbon structure/sp3-C, while the component at 289.7 eV is attributed to the π–
π* shake up satellite of the 284.5 eV peak.
 The peaks at 286.3 eV, 287.2 eV, and 288.4 eV are, respectively, attributed to oxygen
functionalities, namely, C–O, C=O, and COOH
Gulbagh Singh, V. D. Botcha, D. S. Sutar, S.S. Talwar, R.S. Srinivasa and S.S. Major, “Highly reduced
graphene oxide monolayer sheets” (Under Review Under Review in Carbon).

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Conclusion
 Survey Spectra of XPS helps us to detect the element present
on the surface of a material
 The composition of the detected element can be calculated
from the Narrow Spectra
 Sputtering is used to analyze the composition of Depth
Profiles
 Angle Resolved XPS enables us to analyze the depth profiles at
various angles
 Scanning X-ray Imaging (SXI) for secondary electron, images
all conducting and insulating samples
 UPS can be used for work-function, valence band and Fermi
edge measurements

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