1. A FOURIER TRANSFORM INFRARED ABSORPTION STUDY OF HYDROGEN AND DEUTERIUM IN HYDROTHERMAL ZNO -Master presentation 14. Jan 2009 -Hans Bjørge Normann -Web: http://folk.uio.no/hansno/filer/MASTER_Final_15des.pdf

2. Outline  1. Background  Zinc Oxide  Infrared Radiation  Molecular processes  FTIR / Spectrometry  2. Measurements  3. Hydrogen in ZnO  4. Isotopic substitution  5. Results  6. Conclusion

3. FTIR - Introduction  Study the interaction between infrared light and matter  Non destructive  Applications:  Identification of compounds in chemistry  Study impurities in semiconductors

4. Zinc Oxide  Semiconductor with E g =3.4 eV  Hexagonal wurtzite type structure  Our sample dimensions = 10x10x0.5 mm

5. Some ZnO applications  Optical devices  Transparent Conductive Oxide (TCO)  Blue/UV Light Emitting Diodes (LEDs)  Issues  Ohmic and schottky contacts  P-type doping  Growth  Impurities and crystal defects

6. Infrared radiation  Wavenumber http://upload.wikimedia.org/wikipedia/en/8/8a/Electromagnetic-Spectrum.png

7. Molecular processes http://upload.wikimedia.org/wikipedia/en/8/8a/Electromagnetic-Spectrum.png e-e- e-e- Bond breaking and ionization Electronic excitation Vibration Rotation

8. Infrared absorption  IR absorption by defects  Energy is transferred into quantized vibrational excitations

9. 2. Measurements  1. Background  Zinc Oxide  Infrared Radiation  Molecular processes  FTIR / Spectrometry  2. Measurements  3. Hydrogen in ZnO  4. Isotopic substitution  5. Results  6. Conclusion

10. Absorption vs. wavenumber  How can we obtain an intensity scan for many wavenumbers?  2 main methods  Dispersion spectrometer  FTIR

11. Dispersion spectrometer 1. Wavelength separation 2. Slit 3. Sample 4. Detector v 5. Computer I

12. FTIR  The Michelson interferometer principle  1. example: Monochromatic light Detector Movable mirror Stationary Mirror Beamsplitter Interference δ = Optical Path Difference δ = (n + ½) λ δ = n λ

13. FTIR  Dichromatic source v I δ -  -  0  I Moveable mirror

14. FTIR  Broadband source v Continuous IR spectrumInterferogram δ 0 II

15. Fourier Transform Time domain: I vs. δFrequency domain: I vs. v FT δ I v I

16. Advantages of FTIR  Throughput Advantage Circular aperture, high signal intensity → high signal to noise ratio  Multiplex Advantage All frequencies are measured at the same time  Precision Advantage Internal laser control the scanner – built in calibration

17. FTIR @ MiNaLab  Bruker IFS 113v (Genzel type interferometer)  Detection limit ~10 14 - 10 15 cm -3

18. FTIR @ MiNaLab Optical layoutSample holder

19. Measurement  Background spectrum = I 0  Sample spectrum = I I 0 I

20. Fourier Transformed – I vs v

21. Absorbance  Reflectivity  Absorbance and Beer-Lambert Law  d = sample thickness  c = absorbant concentration  α = absorption coefficient

22. 3. Hydrogen in ZnO  1. Background  Zinc Oxide  Infrared Radiation  Molecular processes  FTIR / Spectrometry  2. Measurements  3. Hydrogen in ZnO  4. Isotopic substitution  5. Results  6. Conclusion

23. Hydrogen in ZnO  O-H configurations?  Li···O-H configurations?  O-H stretch modes occurs "always" in the 3200 − 3600 cm − 1 region Shi et. al. Physical Review B, 73(8):81201, 2006 Li et. al. Physical Review B, 78(11), 2008.

24. 4 samples  V85 and V104  Untreated (as-grown) samples  Heat treated at 400 o C for 70 hours  V91  Ion implanted with hydrogen  Heat treated at 400 o C for 70 hours  V92  Ion implanted with deuterium  Heat treated at 400 o C for 70 hours Depth Log concentration

25. 4. Isotopic substitution  1. Background  Zinc Oxide  Infrared Radiation  Molecular processes  FTIR / Spectrometry  2. Measurements  3. Hydrogen in ZnO  4. Isotopic substitution  5. Results  6. Conclusion

26. Isotopic substitution – H and D  Harmonic oscillator approximation  Ratio between O-H and O-D frequency  ω = angular frequency, k = force constant, µ = reduced mass and M,m = mass  O-D modes expected at 2300 − 2600 cm − 1

27. 5. Results  1. Background  Zinc Oxide  Infrared Radiation  Molecular processes  FTIR / Spectrometry  2. Measurements  3. Hydrogen in ZnO  4. Isotopic substitution  5. Results  6. Conclusion

28. DTGS-detector measurements  IR parallel to c-axis of the crystal  As-grown samples

29. Ion-implantation / SIMS O-faceZn-face  H-implantation: E = 1.1 MeV  D-implantation: E = 1.4 MeV  Dose: 2 x 10 16 cm -2 on both sides

30. InSb-detector measurements  IR parallel to c-axis  As-grown samples  Annealed

31. InSb-detector measurements  IR parallel to c-axis  Hydrogen implanted  Annealed  Polished

32. InSb-detector measurements  IR parallel to c-axis  Deuterium implanted  Annealed  Polished

33. InSb-detector measurements  IR perpendicular to c-axis

34. InSb-detector measurements  k perpendicular to c-axis measurements  As-grown and annealed

35. InSb-detector measurements  k perpendicular to c-axis measurements  Hydrogen implanted and annealed / polished

36. InSb-detector measurements  k perpendicular to c-axis measurements  Deuterium implanted and annealed / polished

37. Isotopic shifts

39. Quantification of the hydrogen content...  Integrated absorbance (IA)  Absorption strength per species  D-dose: (1.46 ± 0.54) x 10 17 cm -2  IA (2644 peak): 0.233 cm -2   D = (1.72 ± 0.63) x 10 -18 cm

40. Quantification of the hydrogen content...  Similar treatment on hydrogen is not easy  A conversion factor is needed:  D x C =  H  From other oxides C = 1.31 (LiNbO 3 ), 1.88 (TiO 2 )  Approximation C ZnO ~ 1.595   H = (2.74 ± 1.01) x 10 -18 cm

41.  Integrated absorbace of the 3577 cm -1 peaks   H = (2.74 ± 1.01) x 10 -18 cm  Total H dose introduced: 4 x 10 16 cm -2  Total H dose already present (V85): (2.8 ± 1.0) x 10 16 cm -2 Quantification of the hydrogen content…

42. Possible defect identification  2644 / 3577 cm -1 peaks are assigned a OD-Li /OH-Li complex  The rest of the peaks?  O-H configurations that may be related to vacancies

43. Suggestions for future work  Implantation of higher H-dose  Annealing time  Polarizing filter  Uni-axial stress

44. 6. Conclusion  Eight vibrational modes – excellent isotopic shifts!  In addition, modes at 2613, 3279 and 3483 cm -1  We observe previously unreported O-D modes – close associated with defects involving vacancies  Absorption strength per deuterium species has been determined  Absorption strength per hydrogen species has been approximated  O-H---Li configuration supported by SIMS/FTIR  Introduced amount of H in the same order of magnitude compared to the dose already present

45. Thank You  Prof. Bengt Svensson, Dr. Leonid Murin, Viktor Bobal, Dr. Lasse Vines, Klaus Magnus Johansen, Dr. Jan Bleka, Hallvard Angelskår, Tariq Maqsood, Lars Løvlie, Anders Werner Bredvei Skilbred aka Fru Larsen and Øyvind Hanisch  References  Griffiths and Haseth, Fourier Transform Infrared Spectrometry  Kittel, Introduction to Solid State Physics  Ellmer, Klein, Rech, Transparent Conductive Zinc Oxide  Bruker Optics  Web  http://folk.uio.no/hansno/filer/MasterPres.pdf  http://folk.uio.no/hansno/filer/MasterPres.pptx  http://folk.uio.no/hansno/filer/MASTER_Final_15des.pdf