Two-dimensional and multi-dimensional epitaxy of indium selenide on sapphire

Despite intensive research on the science and technology of atomically thin (two-dimensional) semiconductors, it is still difficult to synthesize at scale such materials. Different synthetic approaches have been used, but it is not always possible to control simultaneously the layer stoichiometry and morphology. Here, we address this challenge within the wide family of indium selenide compounds, “golden challengers” to traditional semiconductor technologies. We demonstrate molecular beam epitaxy of wafer-scale indium selenide on c -plane sapphire. Precise tuning of atomic-fluxes in ultra-high vacuum and desorption-controlled growth are employed for epitaxy of single-phase In 2 Se 3 and InSe layers with atomically smooth surfaces. Multi-dimensional growth is also demonstrated, featuring the formation of In 4 Se 3 nanorods on InSe. The simple geometrical shape of the nanorods arises from the anisotropic crystal structure of In 4 Se 3 and it implies direction-dependent physical properties. These developments position indium selenide as a scalable and versatile material platform with new functionalities and integration capabilities.