Temperature-dependent growth of few layer β-InSe and α-In2Se3 single crystals for optoelectronic device

Controllably selective growth of two-dimensional (2D) layered single crystals plays an important role for their applications in electronic and optoelectronic devices. Among these 2D materials, indium selenide (InxSey), especially InSe and In2Se3, are typical III-VI compound semiconductors which have attracted particular attention due to their excellent electronic transport properties, photoresponse and nonlinear effect. However, controllably selective growth of 2D InSe and In2Se3 by a common method is still a great challenge due to the existence of various stoichiometric substances and crystalline phases of each substance in the indium selenide system. Here, we demonstrate a temperature-dependent chemical vapor transport (CVT) strategy to synthesize few-layer β-InSe and α-In2Se3 single crystals at 400 °C and 450 °C on mica substrate, respectively. A few-layer β-InSe photodetector was fabricated, which displayed high sensitivity to a broad photoresponse range from visible light (500 nm) to near infrared light (850 nm) with a high responsivity of 2103 A W−1 and detectivity of 4.25 × 1012 Jones illuminated by 500 nm. Moreover, we first demonstrate the piezo-phototronic effect of 2D α-In2Se3. The photodetection performance of α-In2Se3 photodetector was increased by 35% with a uniaxial tensile strain of 0.44% under 700 nm light. Our work demonstrates that few-layer β-InSe and α-In2Se3 single crystals can not only be synthesized selectively, but also exhibit excellent optoelectronic properties, which paves a way for their application in optoelectronic and flexible devices.