Solid Phase Epitaxy of Single Phase Two-Dimensional Layered InSe Grown by MBE

Single-phase two-dimensional (2D) indium monoselenide (gamma-InSe) film is successfully grown via solid phase epitaxy in the molecular beam epitaxy (MBE) system. Having high electron mobility and high photoresponsivity, ultrathin 2D gamma-InSe semiconductors are attractive for future field-effect transistor and optoelectronic devices. However, growing single-phase gamma-InSe film is a challenge due to the polymorphic nature of indium selenide (gamma-InSe, alpha-In2Se3, beta-In2Se3, gamma-In2Se3, etc.). In this work, the 2D alpha-In2Se3 film was first grown on a sapphire substrate by MBE. Then, the high In/Se ratio sources were deposited on the alpha-In2Se3 surface, and an gamma-InSe crystal emerged via solid-phase epitaxy. After 50 min of deposition, the initially 2D alpha-In2Se3 phase was also transformed into a 2D gamma-InSe crystal. The phase transition from 2D alpha-In2Se3 to gamma-InSe was confirmed by Raman, XRD, and TEM analysis. The structural ordering of 2D gamma-InSe film was characterized by synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS).

Automated summary

This study successfully grew a single-phase two-dimensional indium monoselenide (γ-InSe) film, which has high electron mobility and high photoresponsivity, making it attractive for future field-effect transistor and optoelectronic devices. The transformation from the initial 2D α-In2Se3 phase to a 2D γ-InSe crystal was achieved by solid-phase epitaxy with controlled deposition time.