ZnxCd1-xS纳米线的可控合成及其可调的光学性质

采用简单的气相沉积法，合成了不同组成的Zn_xCd_1-xS (0< x <1)纳米线. 利用扫描电子显微镜、透射电子显微镜和电子能谱研究了所制得的纳米线的表面形貌和组成. 该方法以Au为催化剂，简单控制起始物质的相对用量和沉积温度，可以获得可控的Zn/Cd 比例. X射线衍射结果表明所制得的Zn_xCd_1-xS纳米线具有纤维锌矿的单晶结构. 根据制得纳米线的表面形貌讨论了纳米线可能的生长机理为“底部生长”机理. 利用拉曼光谱和光致发光光谱研究了Zn_xCd_1-xS纳米线的光学性质，其纵向光学(LO)声子的拉曼位移频率随着组成的变化在ZnS和CdS的拉曼位移频率之间连续变化. 光致发光光谱中同时存在带边发光和缺陷发光. Zn_xCd_1-xS纳米线的带间跃迁的频率可随着组成的调节而调节，纳米线的禁带宽度介于ZnS (3.63 eV)和CdS (2.41 eV)的禁带宽度之间.

Controllable Synthesis of ZnxCd1-xS Nanowires with Tunable Optical Properties

Zn_xCd_1-xS (0< x <1) nanowires with several different compositions were successfully synthesized on Si wafers by a simple vapor deposition method using Au as a catalyst. The morphology and composition of the nanowires were investigated by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results show that the Zn/Cd ratio is controllable by adjusting the relative amount of the starting materials and the deposition temperature. The X- ray diffraction patterns show that the nanowires are single crystals with the wurtzite structure. The morphology character of the nanowires suggests that the growth of the nanowires can be explained by the base-growth mechanism. The optical characteristics of the nanowires were studied by Raman and photoluminescence (PL) spectroscopy. Raman shifts of the longitudinal optical (LO) phonon mode were observed in the Zn_xCd_1-xS nanowires. The LO peak frequency changed smoothly with changing composition, which approximately shows a one-mode behavior pattern in the ZnxCd1- xS nanowires. In the PL spectra, both band-gap and defect emission were observed. The PL results indicate that the emission frequency originating from the band-gap transition of the Zn_xCd_1-xS nanowires can be tuned through modulating of the composition. The band-gap of the nanowires can be tuned from 2.41 eV (CdS) to 3.63 eV (ZnS).