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Thin Film Analysis
Grazing Incidence X-Ray Diffraction
Iuliana Cernatescu
PANalytical Inc.
Westborough, MA, USA
1
Summary
• GIXRD definition• Applications and System Configurations• Examples
2
GRAZING INCIDENCE SCAN
20 30 40 50 60 70 80 90 100 110 120 130 1402Theta (°)
0
400
1600
3600
6400
Inte
nsi
ty (
counts
)
3
Glancing Incidence Diffraction - 2Theta scan
2θ
In the GIXRD scan is fixed at grazing angles
while the 2θ is scanned.
4
Glancing Incidence Diffraction - 2Theta scan
GIXRD 2Theta scan
normal to the diffracting planes
5
Glancing Incidence Diffraction - 2Theta scanGIXRD 2Theta scan
normal to the diffracting planes
6
Glancing Incidence - Diffraction 2Theta scan
GIXRD 2Theta scan
normal to the diffracting planes
7
GIXRD APPLICATIONS AND CONFIGURATION
8
Why use GIXRD?
Total reflection
regime
Absorption limited regime
0 0.5 1.0 1.5
/c
1
10
100
1000
Z0(n
m)
o By changing the incidence angle the x-ray penetration depth into the samples can be changed
o GIXRD provides surface information or depth profiling on randomly oriented polycrystalline materials
X-ray penetration depth
9
Grazing incidence Application Areas
Task or challenges Solution
Weak signal from ultra thin films
GIXRD geometry increases layer signal
Overlapping peaks GIXRD helps distinguish thin film signal from substrate or other layers
Strain/Stress measurement Via GIXRD residual stress can be measured as a function of depth
Phase ID Via GIXRD phase ID analysis can be done at the surface and can be done as a function of depth
Dealing with Textures Samples For Rietveld refinement, size-strain analysis, unit cell refinement the GIXRD geometry gets signal typically from the random oriented grains in the sample
10
GIXRD Configuration
Incident beam optics:
o fixed or programmable divergent and anti-scattering slits
o X-Ray Parabolic Mirror
Diffracted beam optics:
o fixed or programmable receiving and anti-scattering slits
o X-Ray Parabolic Mirror
o Parallel Plate Collimator (0.270, 0.180, 0.090, )
11
GIXRD APPLICATIONS EXAMPLES
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GIXRD for CIGS Solar Cells
W.K. Kim et al. / Journal of Crystal Growth 294 (2006) 231–235
Comparison of GIXRD scan versus conventional symmetrical scan.
In the symmetrical scan a large portion of the diffractogram comes from the substrate, the diffraction peaks of the thin film are barely visible.
In the GIXRD scan the diffraction peaks of the thin film are enhanced.
13
GIXRD - Thin film depth profiling phase analysis
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
400
1600
0
400
1600
0
400
1600
3600
, Incident angle
0.45 deg
1.00 deg
2.00 deg
CIGS
Mo
ZnO
ZnOCIGSZnO
Mo
ZnOCIGSZnO
Mo
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
400
1600
0
400
1600
0
400
1600
3600
14
GIXRD - Thin film depth profiling phase analysis
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
400
1600
0
400
1600
0
400
1600
3600
, Incident angle
0.45 deg
1.00 deg
2.00 deg
CIGS
Mo
ZnO
ZnOCIGSZnO
Mo
ZnOCIGSZnO
Mo
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
400
1600
0
400
1600
0
400
1600
3600
15
GIXRD - Thin film depth profiling phase analysis
Position [°2Theta] (Copper (Cu))
10 20 30 40 50 60 70
Counts
0
400
1600
0
400
1600
0
400
1600
3600
, Incident angle
0.45 deg
1.00 deg
2.00 deg
CIGS
Mo
ZnO=0.45
ZnOCIGSZnO
Mo
=1
ZnOCIGSZnO
Mo
=2
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Example 2 - Surface treatment effect
• Austenitic stainless steels cannot be hardened by heat treatment
• Colossal Carbon Super-saturation Process is one way to harden the austenitic steel:– Carbon diffuses into the steel at elevated to
create compressive residual stress– As the sample cools down some C is released
at very top surface (few nm)– As a result the top few nanometers should
have different d-spacing
17
Depth profiling GIXRD-Austenitic stainless steel
Position [°2Theta] (Copper (Cu))40 50 60 70 80 90 100
Counts
0
1000
020004000
0500
1000
0
1000
0
2000
Incidence angle
0.5 0
0.8 0
1.0 0
2.0 0
0.3 0
18
GIXRD - Austenitic stainless steel – Zoom in
Position [°2Theta] (Copper (Cu))40 45 50 55
Counts
0
1000
020004000
0500
1000
0
1000
0
2000
Incidence angle
0.5 0
0.8 0
1.0 0
2.0 0
0.3 0
19
Unit cell refinement on the GIXRD scan
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Example 3: Residual Stress on thin films, layersUnstressed sample Stressed sample
2θ
Inte
nsi
ty
21
Stress depth gradient
Very small angle of incidence
analyzing stress near surface
Larger angle of incidence
analyzing stress near surface AND deeper
Coating
Substrate
Coating
Substrate
22
Stress with depth in CdTe layer of solar cell
0 2 4 6 8 10 12
-120
-100
-80
-60
-40
-20
Re
sid
ual S
tres
s [M
Pa
]
Grazing Angle [degrees]
20 30 40 50 60 70 80 90 100 110 120 130 1402Theta (°)
0
100
400
900
1600
2500
3600
Inte
nsi
ty (
counts
)
20 30 40 50 60 70 80 90 100 110 120 130 1402Theta (°)
0
400
1600
3600
6400
Inte
nsi
ty (
counts
) 20 30 40 50 60 70 80 90 100 110 120 130 1402Theta (°)
0
400
1600
3600
6400
Inte
nsi
ty (
counts
)
=0.1
=1
=5
23
Conclusions
• GIXRD is a powerful technique which can be used to get information regarding:– Phases present at the surface and as a
function of depth– Strain/Stress at the surface and as a function
of depth– Crystallographic changes at the sample
surface– Enhance layer diffraction signal– Avoid overlapping peaks coming from
different depths on the sample24
