Highly Oriented β-In2S3 Thin Films Grown via Two-Flow-Channel Vertical Chemical Vapor Deposition for Photoconductive Devices

Abstract

β-In2S3 thin films with a defective spinel structure have attracted much attention due to their intriguing optoelectronic properties, yet it remains challenging to synthesize them with high quality and crystallographic orientation. This article reports the highly oriented growth of β-In2S3 thin films according to the symmetry of the sapphire substrate via two-flow-channel vertical chemical vapor deposition (CVD) with an automatic gas supply system. This sophisticated CVD system enables us to control all critical parameters, including reaction temperature, precursor temperatures, and supply amounts of individual precursors, as well as to suppress complex convection, which is vital for the controllable synthesis of β-In2S3 thin films. The crystal quality and oriented growth of the films were confirmed by X-ray diffraction and Raman spectroscopy. In addition, a rigorous method for distinguishing polymorphs of highly oriented In2S3 thin films is discussed to avoid the confusion seen in the literature. The as-fabricated In2S3 photoconductive device shows a high responsivity of 196 A·W–1 and a detectivity of 4.81 × 1011 Jones under white-light irradiation. Our work provides a new CVD method to produce high-quality oriented β-In2S3 thin films for optoelectronic applications.