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A Fourier transform infrared absorption study of hydrogen and deuterium in hydrothermal ZnO

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. Outline. 1. Background Zinc Oxide Infrared Radiation Molecular processes

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A Fourier transform infrared absorption study of hydrogen and deuterium in hydrothermal ZnO

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  1. A Fourier transforminfrared absorption study of hydrogen and deuteriumin 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 Eg=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 e- Bond breaking and ionization Electronic excitation Vibration Rotation http://upload.wikimedia.org/wikipedia/en/8/8a/Electromagnetic-Spectrum.png

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

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

  13. FTIR • Dichromatic source I I v δ - l -l/2 0 l/2 l Moveable mirror

  14. FTIR • Broadband source I I v δ 0 Continuous IR spectrum Interferogram

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

  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 ~1014 - 1015 cm-3

  18. FTIR @ MiNaLab Optical layout Sample holder

  19. Measurement • Background spectrum = I0 • Sample spectrum = I I0 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 Li et. al. Physical Review B, 78(11), 2008. Shi et. al. Physical Review B, 73(8):81201, 2006

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

  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 • H-implantation: E = 1.1 MeV • D-implantation: E = 1.4 MeV • Dose: 2 x 1016 cm-2 on both sides O-face Zn-face

  30. InSb-detector measurements • IRparallel 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-axismeasurements • As-grown and annealed

  35. InSb-detector measurements • k perpendicular to c-axismeasurements • Hydrogen implanted and annealed / polished

  36. InSb-detector measurements • k perpendicular to c-axismeasurements • Deuterium implanted and annealed / polished

  37. Isotopic shifts

  38. Isotopic shifts

  39. Quantification of the hydrogen content... • Integrated absorbance (IA) • Absorption strength per species • D-dose: (1.46 ± 0.54) x 1017 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: Dx C = H • From other oxides C = 1.31 (LiNbO3), 1.88 (TiO2) • Approximation CZnO ~ 1.595 • H = (2.74 ± 1.01) x 10-18 cm

  41. Quantification of the hydrogen content… • Integrated absorbace of the 3577 cm-1 peaks • H = (2.74 ± 1.01) x 10-18 cm • Total H dose introduced: 4 x 1016 cm-2 • Total H dose already present (V85): (2.8 ± 1.0) x 1016 cm-2

  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

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