Gixrd

1. Thin Film Analysis Grazing Incidence X-Ray Diffraction Iuliana Cernatescu PANalytical Inc. Westborough, MA, USA 1

2. Summary GIXRD definition Applications and System Configurations Examples 2

3. Grazing incidence scan 3

4. Glancing Incidence Diffraction - 2Theta scan  2 θ In the GIXRD scan  is fixed at grazing angles while the 2 θ is scanned. 4

5. Glancing Incidence Diffraction - 2Theta scan GIXRD 2Theta scan normal to the diffracting planes 5

6. Glancing Incidence Diffraction - 2Theta scan GIXRD 2Theta scan normal to the diffracting planes 6

7. Glancing Incidence - Diffraction 2Theta scan GIXRD 2Theta scan normal to the diffracting planes 7

8. GIXRD Applications and Configuration 8

9. Why use GIXRD? Total reflection regime Absorption limited regime 0.5 1.0 1.5 / c 1 10 100 1000 Z (nm) By changing the incidence angle the x-ray penetration depth into the samples can be changed GIXRD provides surface information or depth profiling on randomly oriented polycrystalline materials X-ray penetration depth 9

10. 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

11. GIXRD Configuration Incident beam optics: fixed or programmable divergent and anti-scattering slits X-Ray Parabolic Mirror Diffracted beam optics: fixed or programmable receiving and anti-scattering slits X-Ray Parabolic Mirror Parallel Plate Collimator (0.27 , 0.18 , 0.09 , ) 11

12. GIXRD Applications Examples 12

13. 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

14. GIXRD - Thin film depth profiling phase analysis , Incident angle 0.45 deg 1.00 deg 2.00 deg CIGS Mo ZnO  ZnO CIGS ZnO Mo  ZnO CIGS ZnO Mo  14

15. GIXRD - Thin film depth profiling phase analysis , Incident angle 0.45 deg 1.00 deg 2.00 deg CIGS Mo ZnO  ZnO CIGS ZnO Mo  ZnO CIGS ZnO Mo  15

16. GIXRD - Thin film depth profiling phase analysis , Incident angle 0.45 deg 1.00 deg 2.00 deg CIGS Mo ZnO =0.45 ZnO CIGS ZnO Mo =1 ZnO CIGS ZnO Mo =2 16

17. 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

18. Depth profiling GIXRD-Austenitic stainless steel Incidence angle 0.5 0.8 1.0 2.0 0.3 18

19. GIXRD - Austenitic stainless steel – Zoom in Incidence angle 0.5 0.8 1.0 2.0 0.3 19

20. Unit cell refinement on the GIXRD scan 20

21. Example 3: Residual Stress on thin films, layers Unstressed sample Stressed sample   2 θ Intensity 21

22. 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

23. Stress with depth in CdTe layer of solar cell =0.1 =1 =5 23

24. 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 sample 24