Controlled nucleation of monolayer MoSe2 islands on Si (111) by MBE

Abstract

Van der Waals bonding relaxes the constraints of lattice matching, making two-dimensional (2D) transition metal dichalcogenides attractive in the field of epitaxy. Recently, molecular beam epitaxy (MBE) of MoSe2 was demonstrated on a variety of substrates. Here, the authors use MBE to investigate the early stages of 2D nucleation of MoSe2 grown on Si in pursuit of controlled monolayer island size. The 2D nucleation rate varies by a factor of >2 over a narrow substrate temperature range of 550–560 °C. Above 560 °C, the desorption rate of Se from the surface exceeds the nucleation rate leading to fully suppressed 2D monolayer nucleation. X-ray diffraction confirms (001) oriented MoSe2 on Si (111). Raman spectra are consistent with 1–3 monolayer-thick MoSe2, in agreement with atomic force microscopy measurements of the monolayer height of 2D islands.