PNNL

Abstract

Nanowire Formation in Arsenic Trisulfide Brian J. Riley, S.K. Sundaram*, Bradley R. Johnson, Mark Engelhard Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352 * Corresponding author: Phone: 509-373-6665; Fax: 509-376-3108, E-mail: sk.Sundaram@pnl.gov Abstract: Arsenic trisulfide (As2S3) nanowires, nano-droplets, and micro-islands were synthesized on fused silica substrates, using a sublimation-condensation process at reduced pressures (70 mtorr – 70 torr) in a sealed ampoule. Microstructural control of the deposited thin film was achieved by controlling initial pressure, substrate temperature and substrate surface treatment. Microstructures were characterized using scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). Surface topography and chemistry of the substrates were characterized using x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Semi-quantitative image analysis and basic curve-fitting were used to develop empirical models to mathematically describe the variation of microstructure as a function of initial pressure and substrate temperature and map out the regions of different microstructures in P-T space. Thermodyamic properties (available from literature) of this system are also incorporated in this map. Nanowires of an amorphous, transparent in visible-LWIR region, semi-conducting material, like As2S3, provide new opportunities for the development of novel nano-photonic and electronic devices. Additionally, this system provides an excellent opportunity to model (and control) microstructure development from nanometer to micron scales in a physical vapor deposition process, which is of great value to nanoscience and nanotechnology in general.