Venugopal Rayapati, Lin Ping-I, Chen Yit-Tsong
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
J Phys Chem B. 2006 Jun 22;110(24):11691-6. doi: 10.1021/jp056892c.
Zn(x)Cd(1-x)Se alloy nanowires, with composition x = 0, 0.2, 0.5, 0.7, and 1, have been successfully synthesized by a chemical vapor deposition (CVD) method assisted with laser ablation. The as-synthesized alloy nanowires, 60-150 nm in diameter and several tens of micrometers in length, complied with a typical vapor-liquid-solid (VLS) growth mechanism. The Zn(x)Cd(1-x)Se nanowires are single crystalline revealed from high-resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) patterns, and X-ray diffraction (XRD) measurement. Compositions of the alloy nanowires can be adjusted by varying the precursor ratios of the laser ablated target and the CVD deposition temperature. Crystalline structures of the Zn(x)Cd(1-x)Se nanowires are hexagonal wurtzite at x = 0, 0.2, and 0.5 with the [0 1 -1 0] growth direction and zinc blende at x = 0.7 and 1 with the [1 -1 1] growth direction. Energy gaps of the Zn(x)Cd(1-x)Se nanowires, determined from micro-photoluminescence (PL) measurements, change nonlinearly as a quadratic function of x with a bowing parameter of approximately 0.45 eV. Strong PL from the Zn(x)Cd(1-x)Se nanowires can be tuned from red (712 nm) to blue (463 nm) with x varying from 0 to 1 and has demonstrated that the alloy nanowires have potential applications in optical and sensory nanotechnology. Micro-Raman shifts of the longitudinal optical (LO) phonon mode observed in the Zn(x)Cd(1-x)Se nanowires show a one-mode behavior pattern following the prediction of a modified random element isodisplacement (MREI) model.
通过激光烧蚀辅助化学气相沉积（CVD）方法成功合成了组成为x = 0、0.2、0.5、0.7和1的Zn(x)Cd(1 - x)Se合金纳米线。合成的合金纳米线直径为60 - 150 nm，长度为几十微米，符合典型的气-液-固（VLS）生长机制。从高分辨率透射电子显微镜（HRTEM）图像、选区电子衍射（SAED）图案和X射线衍射（XRD）测量结果可知，Zn(x)Cd(1 - x)Se纳米线为单晶。通过改变激光烧蚀靶材的前驱体比例和CVD沉积温度，可以调整合金纳米线的组成。Zn(x)Cd(1 - x)Se纳米线在x = 0、0.2和0.5时的晶体结构为六方纤锌矿结构，生长方向为[0 1 -1 0]，在x = 0.7和1时为闪锌矿结构，生长方向为[1 -1 1]。通过微光致发光（PL）测量确定的Zn(x)Cd(1 - x)Se纳米线的能隙随x呈二次函数非线性变化，弯曲参数约为0.45 eV。随着x从0变化到1，Zn(x)Cd(1 - x)Se纳米线的强PL可以从红色（712 nm）调谐到蓝色（463 nm），这表明合金纳米线在光学和传感纳米技术中有潜在应用。在Zn(x)Cd(1 - x)Se纳米线中观察到的纵向光学（LO）声子模式的微拉曼位移显示出符合修正随机元素等位移（MREI）模型预测的单模行为模式。
