纳米ZnO薄膜的光致发光性质

Photoluminescence Emission Properties of Nanocrystalline ZnO Films

利用溶胶-凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)、吸收谱(ABS)、X射线衍射谱(XRD).X射线衍射(XRD)的结果表明:纳米ZnO薄膜呈多晶状态,具有六角纤锌矿晶体结构和良好的C轴取向.观察到二个荧光发射带,中心波长分别位于395nm的紫带、524nm的绿带和450nm附近的蓝带.证实了纳米ZnO薄膜绿光可见发射带来自氧空位(VO)形成的浅施主能级和锌空位(VZn)形成的浅受主能级之间的复合; 450nm附近的蓝带来自电子从VO的浅施主能级到价带顶或锌填隙(Zn)到价带顶或导带底到V的浅受主能级的复合.

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 substrates, 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 395 nm 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 poly crystalline, and showed sharp diffraction peak for ZnO (002), which indicate that as-sputtered 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.