Growth of Nanometer-Thick & gamma;-InSe on Si(111) 7 x 7 by Molecular Beam Epitaxy for Field-Effect Transistors and Optoelectronic Devices

& gamma;-InSe is a semiconductor that holds promisingpotentialin high-performance field-effect transistors and optoelectronic devices.Large-scale, single-phase & gamma;-InSe deposition has proven challengingbecause of the difficulty in precise control of stoichiometry andthe coexistence of different indium selenide phases. In this study,we demonstrate the wafer-scale combinatorial approach to map out thegrowth window as functions of the Se/In ratio and growth temperaturefor & gamma;-InSe on the Si(111) 7 x 7 substrate in molecularbeam epitaxy. X-ray diffraction (XRD) was used to identify the indiumselenide phases, while atomic force microscopy revealed four distinctsurface morphologies of & gamma;-InSe, enabling a discussion of thegrowth mechanisms associated with each morphology. Cross-sectionalatomic resolution scanning transmission electron microscopy confirmedthat the film was of high crystalline quality and had nearly single-phase & gamma;-InSe. Our comprehensive study elucidates the In-Sephase map for thin film growth parameters, providing invaluable landmarksfor the reproducible synthesis of high-quality & gamma;-InSe layers.