Controlling the Crystallinity of Electrochemically Deposited CdS Nanowires

Abstract

This report describes two distinct growth regimes occurring during the templated electrochemical deposition of CdS nanowires. The abundance of Cd2+ ions at the growth front dictates crystal nucleation and growth processes. At high Cd2+ concentration, randomly oriented polycrystalline material is formed, whereas local depletion of Cd2+ results in highly oriented crystals with the [002] crystalline direction aligned with the nanowire axis. Single nanowires exhibiting both regions were produced for direct imaging of the microstructure associated with these regimes. The current dependence of the time needed to locally deplete Cd2+ allowed for the extraction of a diffusion coefficient for Cd2+ of 1.23 × 10–6 cm2/s, which reflects reduced diffusion in nanoscale channels. Knowledge of these growth regimes and the parameters governing them allows for the growth of materials with targeted structural properties. Specifically, single-crystal materials can be preferentially formed by depositing at relatively high growth currents or by reducing the initial concentration of the Cd precursor in solution.