Arm-Length-Controlled Synthesis, Field Emission, and Luminescence of CdS Multipods

At a low temperature of 550 °C, multiarmed CdS nanostructures were successfully prepared by thermal evaporation of CdS powders without use of any catalysts. The length and tip diameter of the arms in CdS multipods could be controlled by simply varying the growth time. With the arm length increasing, the tip diameter successively decreases. Short-armed multipods (SMPs) are made of both zinc blende and wurtzite phase CdS, while medium-armed multipods (MMPs) and long-armed multipods (LMPs) consist of only hexagonal phase CdS. LMPs exhibit good field-emission (FE) properties with relatively high field-enhancement factor and enhanced luminescence compared to SMPs and MMPs because of the needle-shaped arms and high crystallinity. Besides bind energy emission of CdS, LMPs exhibit a broad red emission in CL spectrum because of the arms with high aspect ratios.