Low-Temperature Solution-Processed Growth of Ternary (BiₓSb₁₋ₓ)₂S₃ Films

Abstract

The development of low-temperature deposition methods for ternary metal chalcogenides is significant for advancing electronics and optoelectronic devices, where precise compositional control remains a key challenge. Here, we report a simple, low-temperature, and scalable in-situ solvothermal technique for the deposition of ternary (Bi1-xSbx)2S3 films using structurally compatible single-source precursors, [Bi{S₂P{O(Pr)₂}₃] and [Sb{S₂P{O(Pr)₂}₃]. This one-pot chemical route facilitates precise control over composition and film quality without the need for additional processing steps. Compositional and structural characterisation confirmed the successful formation of orthorhombic (Bi1-xSbx)2S3 phases across the full composition range (x = 0–1). The systematic shift in X-ray diffraction peak positions and lattice parameters with varying Sb content is consistent with Vegard’s law, indicating the formation of a homogeneous, compositionally tunable ternary alloy. Scanning electron microscopy revealed pronounced morphology changes correlated with the Sb mole fraction, highlighting the influence of composition on microstructural evolution. UV–vis spectroscopy further demonstrated optical tunability, with bandgaps increasing from 1.82 to 2.04 eV as Sb content increased. These results underscore the effectiveness of precursor ratio adjustment for controlling final film composition and properties, showcasing the versatility of this low-temperature solvothermal approach for synthesising phase-pure, compositionally engineered mixed-metal chalcogenide thin films.