Photoluminescence Emission Properties of Nanocrystalline ZnO Films
纳米ZnO薄膜的光致发光性质

Nanocrystalline ZnO films is a promising material for short-wave laser and luminescence etc, due to its wide band gap (3.37 eV) and high exciton binding energy(60 meV)at room temperature.Nanocrystalline ZnO films is prepared by using sol-gel, grow on a quartz glass subtractes, Photoluminescence spectra and Absorption spectra of nanocrystalline ZnO films with excitation wavelength 365 nm are measured at room temperature.Two emission bands are observed, one being a narrow violet band its central wavelength is 395nm and the other being wide visible band its central wavelength is 524 nm, 450 nm.Crystal structure of samples are examined by X-ray diffraction (XRD) pattern, the mean grain size of nanocrystalline ZnO films are calculated by with Debye-Scherrer formula.The results indicate that nanocrystalline ZnO films has a hexagonal wurtzite structure and polycrystalline, and showed sharp diffraction peak for ZnO(002),which indicate that as-sputered film were highly c-axis oriented.In particular the mechanism behind the visible luminescence has also been discussed in this paper.It should be said that the mechanism behind the visible luminescence is still a question of debate.In this paper the visible emission processes of nanocrystalline ZnO.The experiments prove that the luminescence emission peak located 524 nm corresponds to the transition from the shallow level of oxygen vacancy to the shallow level of zinc vacancy; and the luminescence emission peak located 450 nm corresponds to the transition from the shallow level of oxygen vacancy to valence band or the interstitial or conductor band to the shallow level of zinc vacancy.