Kum Maxwell C, Yoo Bong Young, Rheem Young Woo, Bozhilov Krassimir N, Chen Wilfred, Mulchandani Ashok, Myung Nosang V
Department of Chemical and Environmental Engineering and Center for Nanoscale Science and Engineering, University of California, Riverside, CA 92521, USA.
Nanotechnology. 2008 Aug 13;19(32):325711. doi: 10.1088/0957-4484/19/32/325711. Epub 2008 Jul 4.
CdTe nanowires with controlled composition were cathodically electrodeposited using track-etched polycarbonate membrane as scaffolds and their material and electrical properties were systematically investigated. As-deposited CdTe nanowires show nanocrystalline cubic phase structures with grain sizes of up to 60 nm. The dark-field images of nanowires reveal that the crystallinity of nanowires was greatly improved from nanocrystalline to a few single crystals within nanowires upon annealing at 200 °C for 6 h in a reducing environment (5% H(2)+95% N(2)). For electrical characterization, a single CdTe nanowire was assembled across microfabricated gold electrodes using the drop-casting method. In addition to an increase in grain size, the electrical resistivity of an annealed single nanowire (a few 10(5) Ω cm) was one order of magnitude greater than in an as-deposited nanowire, indicating that crystallinity of nanowires improved and defects within nanowires were reduced during annealing. By controlling the dopants levels (e.g. Te content of nanowires), the resistivity of nanowires was varied from 10(4) to 10(0) Ω cm. Current-voltage (I-V) characteristics of nanowires indicated the presence of Schottky barriers at both ends of the Au/CdTe interface. Temperature-dependent I-V measurements show that the electron transport mode was determined by a thermally activated component at T>-50 °C and a temperature-independent component below -50 °C. Under optical illumination, the single CdTe nanowire exhibited enhanced conductance.
以径迹蚀刻聚碳酸酯膜为支架，阴极电沉积出成分可控的碲化镉纳米线，并对其材料和电学性质进行了系统研究。沉积态的碲化镉纳米线呈现出纳米晶立方相结构，晶粒尺寸可达60纳米。纳米线的暗场图像显示，在还原环境（5% H₂ + 95% N₂）中于200℃退火6小时后，纳米线的结晶度从纳米晶大幅提高到纳米线内的少数单晶。为了进行电学表征，采用滴铸法在微纳加工的金电极上组装了一根碲化镉纳米线。除了晶粒尺寸增加外，退火后的单根纳米线的电阻率（几十10⁵ Ω·cm）比沉积态纳米线大一个数量级，这表明纳米线的结晶度提高，且退火过程中纳米线内的缺陷减少。通过控制掺杂剂水平（如纳米线的碲含量），纳米线的电阻率在10⁴到10⁰ Ω·cm之间变化。纳米线的电流-电压（I-V）特性表明在金/碲化镉界面两端存在肖特基势垒。与温度相关的I-V测量表明，在T > -50℃时，电子传输模式由热激活成分决定，而在低于-50℃时由与温度无关的成分决定。在光照下，单根碲化镉纳米线表现出增强的电导。
