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

Abstract

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

Growth of Nanometer-Thick γ-InSe on Si(111) 7 × 7 by Molecular Beam Epitaxy for Field-Effect Transistors and Optoelectronic Devices

“…The scalability down to a single layer accompanied by the BEOL-friendly synthesis parameters makes InSe a promising candidate as a channel material in high-performance, ultrathin body field-effect transistors (FET). , To date, exfoliation from a single crystal is the most commonly used approach to study the electronic properties of InSe, ,,,,− while large-scale synthesis with precisely controlled thickness is still required for realistic industry purposes. Thin film synthesis techniques like pulsed laser deposition, , physical vapor deposition, , metal–organic chemical vapor deposition, , and molecular beam epitaxy (MBE) have successfully been demonstrated for InSe thin film growth. − MBE has advantages over other methods in growing high-quality crystalline InSe films, as it excels in precise control of atomic flux, growth temperature, and deposition rate. Despite the strength of precise control of growth parameters, growing a phase pure InSe film generally requires an extensive growth window mapping process.…”