Growth of quasi-1 dimensional (Bi_1−x Sb _x )₂S₃ nanowires on fluorine-doped tin oxide glass substrate by vapor transport

Abstract (Bi_1−xSb _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.