Zinc oxide (ZnO) is a wide band gap (3.4eV at 300K) II-VI semiconductor with an exciton binding energy up to 60meV and is promising in the realization of excitonic or polaritonic lasing effect. Photoluminescence is widely used in studying the band gap and defect levels of ZnO. However, understanding in defects of ZnO is still far from satisfaction and remains controversial. Different authors suggest different explanations and mechanisms. 　In the present study we investigate in the photoluminescence spectra of four kinds of ZnO single crystal, namely as-grown (not implanted) Zn-face polished, Zn-implanted, O-implanted and He-implanted. The samples are annealed both in air and argon gas at a temperature of 350, 650, 750, 900 and 1200oC. The results show that O-implanted sample is weaker in excitonic emission and has an annealing effect tendency not consistent with that of Zn-implanted and He-implanted. Ion implantation would introduce defects in favor of yellow luminescence and the defects would anneal out gradually as the annealing temperature is rising. / published_or_final_version / Physics / Master / Master of Philosophy

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Photoluminescence spectroscopy of bulk zinc oxide under different annealing conditions was examined. The effect of the annealing atmosphere, temperature and time on the optical properties of zinc oxide were studied to investigate the influence on the intrinsic defects present. The wafers used were bulk +c ZnO grown by Tokyo Denpa using the hydrothermal technique. The annealing effect on both zinc and oxygen faces was investigated. The dominant donor bound exciton related to aluminum, labelled in the literature as I₆ demonstrated a splitting of 0.3 meV. The origin of this splitting has been linked to an interaction between aluminum and hydrogen, through its reaction to atmospheric dependent annealing. The removal of the hydrothermal hydrogen peak at 3.3624 eV has uncovered some fine structure. After Arrhenius analysis of this fine structure it was shown it is excited states of bound excitons. This fine structure has been loosely associated with vibrational and rotational excited states. The behaviour of all the optical features present in the photoluminescent spectra under annealing has a relation with the carrier concentration of the samples.

Zinc oxide is a familiar ingredient in common household items including sunscreen and medicines. It is, however, also a semiconductor material. As such, it is possible to use zinc oxide (ZnO) to make semiconductor devices such as diodes and transistors. Being transparent to visible light in its crystalline form means that it has the potential to be the starting material for so-called 'transparent electronics', where the entire device is transparent. Transparent transistors have the potential to improve the performance of the electronics currently used in LCD display screens. Most common semiconductor devices require the material to be selectively doped with specific impurities that can make the material into one of two electronically distinct types – p- or n-type. Unfortunately, making reliable p-type ZnO has been elusive to date, despite considerable efforts worldwide. This lack of p-type material has hindered development of transistors based on this material. One alternative is a Schottky junction, which can be used as the active element in a type of transistor known as a metal-semiconductor field effect transistor, MESFET. Schottky junctions are traditionally made from noble metal layers deposited onto semiconductors. Recent work at the Canterbury University has shown that partially oxidised metals may in fact be a better choice, at least to zinc oxide. This thesis describes the development of a fabrication process for metal-semiconductor field effect transistors using a silver oxide gate on epitaxially grown zinc oxide single crystals. Devices were successfully produced and electrically characterised. The measurements show that the technology has significant potential.

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Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [133]-140).