Maxwell C. Kum1, Bongyoung Yoo2, Youngwoo Rheem1, Krassimir N. Bozhilov3, Wilfred Chen1, Ashok Mulchandani4, and Nosang V. Myung1. (1) Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521, (2) Division of Materials and Chemical Engineering, Hanyang University, Ansan, South Korea, (3) Central Facility for Advanced Microscopy and Microanalysis, University of California, Riverside, Riverside, CA 92521, (4) Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521
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 size 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 hrs in a reducing environment (5 % H2 + 95 % N2). For electrical characterization, single CdTe nanowire was assembled across microfabricated gold electrodes using drop-casting method. In addition to increase in grain size, the electrical resistivity of an annealed single nanowire (a few 105 ohm cm) was one order of magnitude greater than 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 were varied from 104 to 100 ohm cm. Current-voltage (I-V)characteristics of nanowire 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.