生长ZnO薄膜的氧分压对ZnO/PS体系光学性能的影响

Effects of oxygen partial pressure for ZnO film growth on luminescent properties of ZnO/PS nanocomposite systems

采用电化学阳极氧化法,在p型（100）晶向的单晶Si片上制备多孔Si（PS）样品;以PS为衬底,采用射频反应磁控溅射技术在不同O2分压下沉积ZnO薄膜。X射线衍射（XRD）结果显示,所有ZnO/PS复合体系在衍射角为34.24°附近均出现较强的衍射峰,对应于ZnO的（002）晶面,说明样品具有良好的c轴择优取向;但由于衬底PS粗糙的表面结构,衍射峰的半高全宽（FWHM）都较大。扫描电子显微镜（SEM）形貌显示,ZnO颗粒完全覆盖了PS的孔洞。从室温下测得样品的光致发光（PL）谱观察到,ZnO/PS复合体系在可见光区（400~700 nm）形成一条宽的PL带,其包括ZnO的蓝、绿光峰及PS的红橙光峰,且发光强度随O2分压的减小先增强后减弱,ZnO的蓝、绿光与PS的红橙光叠加,呈现出较强的白光发射。经分析得出,在O2∶Ar为6∶10 sccm气氛中制备ZnO/PS复合体系的发光效率最高。

Porous silicon（PS） samples were formed by the electrochemical anodization on the p-type（100） silicon wafer,and ZnO films were deposited on the PS substrates at different oxygen partial pressures by the radio frequency（RF） reactive magnetron sputtering technique.X-ray diffraction（XRD） patterns show that all samples（ZnO/PS） have a diffraction peak at about 34.24° corresponding to the ZnO（002） direction,which indicates that ZnO films have a preferential c-axis orientation,but the full width at half maximum（FWHM） of the diffraction peak is large due to the roughness of the PS surface.Scanning electron microscope（SEM） images show that ZnO particles completely cover the pores of PS.The results of photoluminescence（PL） spectra at room temperature show that ZnO/PS nanocomposite systems form a broad PL band,including the blue and green emissions from ZnO and the red-orange emission from the PS.With the decrease of oxygen partial pressure,the intensity of emission peak of samples（ZnO/PS） first increases and then decreases.Combining the blue and green emission from ZnO and the red emission from PS,the white light emission was obtained.The analysis shows that the most intense luminescence is obtained from the sample grown at the O2∶Ar ratio of 6∶10 sccm.