LASER ABSORPTION % FOR Si & SiC

1. LASER ABSORPTION % FOR Si & SiC Amir Rahimpour Shayan Huseyin Bogac POYRAZ Supervisor : Dr John Patten 10/17/2008

2. Objective • To determine the optical properties (such as absorptance%, reflectance% and transmittance%) of Si and SiC (3C, 4H and 6H SiC) at normal pressure for 500 nm,1000 nm and 1500 nm wavelength.

3. Procedure Used • Dielectric constants • ε1=n2 –k2 • ε2=2*n*k • Dispersion relations • β2–(α2/4)=(ω2/c2)*ε1 • α*β=(ω2/c2)*ε2 • Reflection coefficient • R=((n-1)2+k2)/((n+1)2+k2)

4. Procedure Used cont’d • % Transmission • % Absorption

5. Procedure Used cont’d •  Detailed analysis for the selection of an appropriate laser wavelength was made. •  The absorption% for three distinct wavelengths namely 500 nm, 1000nm and 1500 nm at various thickness of the workpiece sample was calculated for: • Si-I at normal pressure • Si-II (HPP) at 13.2 GPa • 3C-SiC (at normal pressure) • 4H-SiC (at normal pressure) • 6H-SiC (at normal pressure)

6. Optical Prop. of Silicon (Si-I)(under normal pressure) For laser wavelength of 500 nm Average Absorption %  61

7. Optical Prop. of Silicon (Si-I)(under normal pressure) For laser wavelength of 1000 nm Average Absorption %  41

8. Optical Prop. of Silicon (Si-I) (under normal pressure) For laser wavelength of 1500 nm Average Absorption %  0.5

9. Optical Prop. of Silicon (Si-I) (under normal pressure) WAVELENGTH (nm)

10. Optical Prop. of Silicon II (Si-II) (under high pressure of 13.2 GPa) For laser wavelength of 500 nm Average Absorption %  51

11. Optical Prop. of Silicon II (Si-II) (under high pressure of 13.2 GPa) For laser wavelength of 1000 nm Average Absorption %  23

12. Optical Prop. of Silicon II (Si-II) (under high pressure of 13.2 GPa) For laser wavelength of 1500 nm Average Absorption %  10

13. Optical Prop. of Silicon II (Si-II) (under high pressure of 13.2 GPa) WAVELENGTH (nm)

14. Comparing Si-I and Si-II 61.3 51 40.5 23 10 0.49 WAVELENGTH (nm)

15. Optical Prop. of 3C-SiC(normal pressure) For laser wavelength of 500 nm Average Absorption %  99

16. Optical Prop. of 3C-SiC(normal pressure) For laser wavelength of 1000 nm Average Absorption %  99

17. Optical Prop. of 3C-SiC(normal pressure) For laser wavelength of 1500 nm Average Absorption %  95

18. Optical Prop. of 3C-SiC(normal pressure) WAVELENGTH (nm)

19. Optical Prop. of 4H-SiC(normal pressure) For laser wavelength of 500 nm Average Absorption %  29

20. Optical Prop. of 4H-SiC(normal pressure) For laser wavelength of 1000 nm Average Absorption %  20

21. Optical Prop. of 4H-SiC(normal pressure) For laser wavelength of 1500 nm Average Absorption %  17

22. Optical Prop. of 4H-SiC(normal pressure) WAVELENGTH (nm)

23. Optical Prop. of 6H-SiC(normal pressure) For laser wavelength of 500 nm Average Absorption %  14

24. Optical Prop. of 6H-SiC(normal pressure) For laser wavelength of 1000 nm Average Absorption %  86

25. Optical Prop. of 6H-SiC(normal pressure) For laser wavelength of 1500 nm Average Absorption %  86

26. Optical Prop. of 6H-SiC(normal pressure) WAVELENGTH (nm)

27. Comparing SiC (3C, 4H & 6H) 99.3 99.6 94.7 85.6 86.2 28.5 20 17.1 13.8 WAVELENGTH (nm)

28. CONCLUSION • Absorption% for 1500 nm laser wavelength for Si-II is much higher when compared to Si-I. • Si-I has the highest average absorption% at 500 nm wavelength (61%). • Si-II has the highest average absorption% at 500 nm wavelength (51%). • By applying pressure (13.2GPa) the average absorption% of Si at 500 nm wavelength drops by 10%. • At 1500 nm wavelength absorption of Si-I is almost zero.

29. CONCLUSION • The average absorption% for 3C-SiC remains constant above 95% with increasing the wavelength from 500 nm to 1500 nm. • The average absorption% for 4H-SiC decreases slightly with increasing the wavelength from 500 nm to 1500 nm. • In case of 6H-SiC the absorption% largely depends on wavelength and increases from 14% to 86% on increasing wavelength from 500 nm to 1000 nm. After that it becomes constant up to 1500 nm wavelength. • 3C-SiC has the highest average absorption% (≥95%) at all wavelengths (500, 1000 and 1500 nm) comparing w/ 4H-SiC and 6H-SiC.

30. Acknowledgement • We would like to thank Dr Alvin Rosenthal (from Physics Dept., WMU) and HimanshuLohani for their great assistance.

31. FUTURE WORK • To determine the optical properties (such as absorption%, reflectivity% and transmittance%) SiC (3C, 4H and 6H SiC) at high pressure for 500 nm,1000 nm and 1500 nm wavelengths.

32. REFERENCES • “Handbook of Optical Constants of solids”, D.Palik, http://www.ee.byu.edu/photonics/opticalconstants.phtml • “Optical properties of selected elements” by J.H .Weaver and H.P.R. Frederikse. • “Optical properties of Metallic Silicon” by M.Hanfland, M. Alouani, K. Syassen and N.E. Christensen. • “Optical properties of crystalline semiconductors and dielectrics” by A.R.Forouhi and I. Bloomer. • “Dielectric functions of bulk 4H and 6H SiC and spectroscopic ellipsometry studies of thin SiC films on Si”, S. Zollner, J. G. Chen, E. Duda, T. Wetteroth, S. R. Wilson, and J. N. Hilfiker, J. of APP. PHYS. V. 85, Num. 12, JUNE 1999. • “Optical properties of cubic silicon carbide” by A.D. Laine, A.M. Mezzasama, G. Mondio, P. Parisi, G. Cubiotti, Yu.N. Kucherenko, J. of Electron Spectroscopy and related Phenomena 93 (1998) 251-257. • “Optical properties of cubic silicon carbide” by A.D. Laine, A.M. Mezzasama, G. Mondio, P. Parisi, G. Cubiotti, Yu.N. Kucherenko, J. of Electron Spectroscopy and related Phenomena 93 (1998) 251-257.

33. THANK YOU Questions