Growth of quasi-1 dimensional (Bi1−x Sb x )2S3 nanowires on fluorine-doped tin oxide glass substrate by vapor transport

Abstract

Abstract (Bi1−x Sb x )2S3 solid solution nanowires ( 0 ≤ x ≤ 0.73 ) are grown on fluorine-doped tin oxide (FTO) glass via physical vapor transport. The compositions were controlled by varying the Sb2S3 source temperature (300 °C–453 °C) by changing the upstream locations of the Sb2S3 source in the furnace while keeping the Bi2S3 source at the center of the furnace (497 °C). Defect-free nanowires with phase-pure orthorhombic and quasi-1 dimensional crystal structures were grown under a modified vapor–solid mechanism affected by FTO at initial growth stage. The aspect ratios of the nanowires reached the minimum at composition x ∼ 0.6 . As the Sb2S3 source approached the Bi2S3 source, x increased owing to the increase in the Sb2S3 source temperature. x/(1-x), which is proportional to the evaporation flux of the Sb2S3 source, could be well-fitted with a thermally activated equation with an apparent activation energy ( 105 kJ mol - 1 ). However, at the distance between the Sb2S3 and Bi2S3 sources, with the Sb2S3 source at temperatures higher than 410 °C, the compositions reduced despite the increased Sb2S3 evaporation flux. Such retrograde behavior was confirmed by high-resolution transmission electron microscopy, x-ray diffraction, and micro-Raman studies. This retrograde behavior is ascribed to the loss due to the reaction of gaseous Sb species with the Bi2S3 source.