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Hot phosphor acid (H3 PO4) etching and/or SiOxNy surface passivation are used to change the surface states of high-resistance intrinsic GaN films. The films are investigated to reveal the influence of controlled surface states on photoluminescence (PL) emission. It is found that H3 PO4 etching cannot improve the ultraviolet (UV) PL emission obviously, but the PL spectrum in the range of visible light is considerably enhanced. After passivation with SiOxNy film, the quantum efficiency of UV PL is increased by a factor of 12-13. Meanwhile, the visible PL is significantly enhanced. By analyzing the PL spectra of the etched and passivated samples obtained at room temperature and low temperatures, we discuss the role of surface states in PL emission in the range of UV, blue and yellow bands, and the related physical mechanisms.

N-doped Cu2O films are deposited at different temperatures by sputtering a CuO target in the mixture of Ar and N2. By the analysis of transmission spectra, it is found that the N-doped Cu2O films are changed into a direct allowed band-gap semiconductor and the optical band gap energy is enlarged to 2.52±0.03 eV for the films deposited at different temperatures. The first-principles calculations indicate that the energy band gap increase by 25%, which is in good agreement with the experimental result. The change from a direct forbidden band-gap transition to a direct allowed band-gap transition can be attributed to the occupation of 2p electrons of N at the top of valence band in the N-doped Cu2O film.

Zn1-xMgxO films have been deposited on Al2O3(0001) substrates at different oxygen pressures by using pulsed laser deposition method. The influence of oxygen pressure on the crystal quality and optical properties of the films is studied with X-ray diffraction (XRD), transmittance spectra, and photoluminescence (PL). It is found that the crystal quality of the films lowers with increasing of oxygen pressure from 10-4Pa to 10 Pa. At the pressure of 10-4 Pa, the epitaxial relationship between the film and sapphire substrate is determined to be ZnMgO (0001)// Al2O3(0001),ZnMgO 1010]//Al2O3 1120]. In the oxygen rich environment, however, another epitaxial relationship, ZnMgO (0001)//Al2O3(0001) and ZnMgO 1010]//Al2O3 1010], is also present in the films, which is suggested to be responsible for the decline of the crystal quality. Compared with pure ZnO films, the UV peak of Zn1-xMgxO alloys shows red-shift from 3.374 to 3.332 eV with increasing oxygen working pressure increasing from 10-4 Pa up to 10 Pa. The difference in red-shifts can be attributed to the decrease of Mg content in the films resulting from the variation of oxygen pressure. A broad UV PL spectrum was observed at 10 K in the films deposited under different pressures and can be decomposed into two recombination processes of excitons, corresponding to the bound and the localized exciton luminescence, respectively. The binding energy of bound excitons in the ZnMgO films is larger than that in pure ZnO and has an increasing trend with increasing oxygen pressure.

ZnO/MgO multi-quantum wells with modulation structure are grown on oxidated Al2O3 （0001） substrates using radio-frequency reactive magnetron sputtering method. X-ray reflectivity and X-ray diffraction measurement，electronic probe，atom force microscopy，transmission spectrum and PL spectrum are used to characterize the samples. The XRD scan and phi-scan results show the films are highly （001） textured and have epitaxial relationship with the substrates. The width of quantum well is determined to be between 838 nm and 2178 nm by XRR and EPMA. The AFM results show that the RMS roughness of the MQWs increases from 64 nm to 212 nm with the decrease of period of modulation. Low temperature PL spectrum shows the peak can be assigned to the radiative recombination of bound excitons，and the activation energy is estimated to be about 30 meV. The emission due to spatially separated carriers caused by quantum-confined Stark effect is also found in the spectrum of sample with smaller well width.

ZnO thin films with strong c-axis preferred orientation have been deposited on Ti buffered Si （111） substrate by reactive ratio-frequency magnetron sputtering. With X-ray diffraction analysis and photoluminescence （PL） measurement， the structure， residual stress and PL emission properties of Ti-buffered ZnO films are studied and effects of Ti-layer thickness and annealing temperature are discussed. It is found that the PL properties of the films are improved after the introduction of Ti buffer layer and an optimized thickness of Ti buffer layer is given. Annealing treatment can improve the properties of Si（111）/Ti-buffer/ZnO films further. The residual stress is found to be an important factor influencing the emission properties of ultraviolet light. It is helpful for the emission of ultraviolet light if the films have a small residual stress. The residual stress can also change the transition energy of excitons. With the increase of annealing temperature， the increase of tension strain in films reduces the band gap of ZnO， hence results in the shift of the excitonic peak to lower energy.

Si（001） chips were implanted by Zn ions of 40 keV with different ion dosages and are annealed in air at different temperatures. Atomic force microcopy， transmission electron microcopy， X-ray diffraction and electron probe are applied to study the microstructure， morphology and chemical composition of the chips, either as-implanted or annealed at different temperatures. It was found that the as-implanted Zn atoms aggregate into clusters scattering about 35 nm beneath the surface of the chips. During the annealing process， Zn atoms are found to migrate towards the surface of the chips and aggregate into nanoparticles at the interface between the amorphous SiO2 layer and polycrystal line Si layer. Annealing temperature was found to be the crucial factor controlling the formation of ZnO nanoparticles. ZnO nanoparticles begin to appear at about 400 ℃ and the diffraction intensity of ZnO becomes strong while the diffraction intensity of metallic Zn weakens with increasing annealing temperature. At the annealing temperature of 800 ℃， Zn2SiO4 phase was observed due to the reaction between ZnO and SiO2 or Si.