Control of Lateral Epitaxial Nanothin β-In₂Se₃ Grown by Molecular Beam Epitaxy: Implications in Fabricating of Next-Generation Transistors

This study was meticulously conducted, delving into the epitaxial growth of nanothin β-In₂Se₃ films on sapphire (0001) using molecular beam epitaxy. The growth temperature was carefully set at 480 °C, and the selenium to indium flux ratio (R_Se/In) was systematically varied from 1 to 100. The phase transformation from γ-In₂Se₃ to β-In₂Se₃ was precisely controlled by manipulating the R_Se/In and confirmed through Raman scattering measurements and synchrotron-based grazing-incidence wide-angle X-ray scattering. The surface morphology for various R_Se/In of In₂Se₃ was analyzed by atomic force microscopy (AFM). The lowest surface roughness is around 0.58 nm, which is achieved under the R_Se/In = 60 growth condition. The nanothin β-In₂Se₃ film with a layer-by-layer atomic arrangement was verified by high-resolution transmission electron microscopy. According to the experimental results, the growth dynamics of In₂Se₃ are proposed to be step-flow growth and horizontal growth under R_Se/In 45 and 60 conditions, respectively. This research underscores the control of the growth mechanism by Se/In flux and its role in facilitating the In₂Se₃ epitaxy for integration in the development of 2D-materials-based future electronic devices.