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URN etd-0818111-095754 Statistics This thesis had been viewed 2054 times. Download 747 times. Author Hsi-Jung Huang Author's Email Address email@example.com Department Electro-Optical Engineering Year 2010 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 75 Title P-type Behavior in Cu-Ga Codoped ZnO Epilayers Grown by Plasma-Assisted Molecular Beam Epitaxy Keyword PA-MBE Cu-Ga codoped ZnCuO p-type ZnO p-type ZnO ZnCuO Cu-Ga codoped PA-MBE Abstract In this work, we demonstrate the p-type ZnO epilayers with Cu-Ga co-doped method by using plasma-assisted molecular beam epitaxy (PA-MBE). It is difficult to fabricate the p-type ZnO by mono-doped Cu due to the extremely rare solid solubility of Cu and hardly controlled the valence number of Cu. The X-ray diffraction (XRD), photoluminescence, Raman scattering, and Hall measurement are employed to characterize the efficacy of co-doped Ga and Cu. In a few Cu content, i.e. lower Cu element flux, XRD and PL reveal the improved crystal quality due to similar ionic radius of Cu2+ (0.73 Ả) and Zn2+ (0.74 Ả). In PL result, the free-exciton-emission (FX) is obvious and the full-width at half maximum (FWHM) of donor-bound-exciton-emission (D0X) reduces from 8.63 meV (ZnO) to 6.05 meV. The ZnO E1 mode signal (433 cm-1) is enhanced in Raman spectrum. XRD patterns of Zn1-xCuxO (0 ≤ x < 0.66) epilayers were displayed the wurtzite and cubic structure co-exist when the Cu cell temperature (TCu)= 1100 oC. The ZnCuO epilayers of TCu from 700oC to 1200oC are all demonstrated n-type. The carrier concentration is reduced with increasing Cu flux from -5.0 × 1017 cm-3 to -4.3 × 1013 cm-3. However, the p-type ZnO epilayers are demonstrated by co-doped Ga into ZnCuO and the carrier concentration is around 5×1014 cm-3.
Furthermore, we report the characterization of nano-size ZnO powder synthesized via microwave assisted heating of Zn(CH3COO)2•2H2O and NaHCO3 solution with deionized water as the solvent. The as-synthesized ZnO powder was calcined at temperatures from 400 to 800oC for 8 hr. The XRD and Fourier transform infrared spectroscopy (FTIR) spectra revealed pure wurtzite structure for the ZnO nanopowder (NP) calcined at 800oC. Scanning electron microscopy (SEM) images showed that the size and uniformity of ZnO NP increases with the calcination temperature raising. Significant UV emission at 373 nm has been observed in the PL spectra of the as-synthesized and calcined ZnO NP. Enhanced PL intensity and reduced FWHM for ZnO NP synthesized at higher calcination temperature are shown in our results. According to this base, we synthesize the MgZnO nanopowders with different Mg contents by the microwave heating technique. The difference between the designed, estimated Mg content, and different orders of adding in the synthesized samples are discussed.
Advisor Committee Chu-Shou Yang - advisor
Chih-Wei Luo - co-chair
Min-De Yang - co-chair
Woo-Hu Tsai - co-chair
Files Date of Defense 2011-07-19 Date of Submission 2011-08-18