| Semiconductor material zinc oxide (ZnO) has attracted much attention in the past decade, due to its excellent physical properties and broad range of potential applications on opto-electronic devices, surface acoustic wave devices, piezoelectric and pyroelectric devices. In this dissertation, we used 248 nm KrF excimer laser to irradiate the ZnO single crystals with different laser energy densities. The relationship between the physical properties and irradiated laser energy densities were investigated. The physical properties include the structure dynamics, elastic and piezoelectric constants, and optical properties. Besides that, polarized photoluminescence spectra of the nonpolar ZnO single crystals annealed at different temperature in air were also investigated, for which the whole emission spectra from visible up to ultraviolet range for zinc and oxygen defects states are taken separately via. the parallel and the crossed polarization geometries, respectively. The main results are listed as follows. From the result of photoluminescence study on irradiated ZnO single crystal at different laser energy densities, it is found that structure and PL properties of the strongly depend on laser energy densities. Then for polarized PL measurements, the whole PL spectra from visible up to ultraviolet (UV) range for zinc and oxygen defect states are taken separately via. the parallel and the crossed polarization geometries, respectively. It is found that the defect centers which consisted the deep band emission (DBE) band in visible region, exhibit their own polarities through the polarization selection.While for the results of Raman scattering study, it is found that more high-order Raman modes have been observed and assigned due to the spectra with high ratio of signal-noise and high resolution. It is helpful to the researching on structure defects and origin of additional Raman modes in irradiated ZnO single crystals. The Raman spectra of ZnO single crystals irradiated with different laser energy densities have been taken over the frequency range of 80 to 1300 cm-1. Two additional modes (AMs), as clearly observed around 275 and 552 cm-1, are assigned to be silent modes in wurtzite-ZnO, while the other AMs are associated to the combination of these two silent modes with the LO and TA phonon modes, and based on the result of z-Mapping carried out on a ZnO single crystal irradiated at 500 mJ/cm2, the depth of laser irradiated layer is around 10μm. Furthmore, the contact-induced deformation behavior of optical phonons in ZnO single crystal (wurtzite) is investigated using a combination of nanoindentation with a Berkovich indenter and polarized Raman spectroscopy, in order to explain the unharmonious effects observed in the spectra of irradiated ZnO single crystals, and the defects existed in irradiated samples.And final, from the velocity of sound measurements by Brillouin scattering technique, the whole set of elastic and piezoelectric constants of the ZnO single crystals for as grown and irradiation at different laser energy densities have been determined, in the micron range of irradiated layer thicknesses. Our results show that the physical properties corresponding to acoustic phonon modes strongly depend on laser energy densities. It was found that under appropriate laser conditions, 248 nm KrF excimer laser irradiation can significantly improve the surface quality of the irradiated ZnO crystal, as well as the elastic and piezoelectric properties were also increased. The process has potential applications in the fabrication of ZnO-based surface acoustic wave and optic-electronic devices. On the contrary, too high laser fluence would induce surface damage of ZnO probably due to laser ablation of the sample surface, and produce structural defects, then lead to the reduction in the elastic and piezoelectric constants.
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