Nanoscale MoSe2 Grown on Si(111) for Potential Applications in Broadband Photodetectors

Molybdenum diselenide (MoSe2)/silicon (Si) heterostructures hold promise for advanced devices with improved performance, especially broadband photodetectors with a fast response. In this study, we investigate the impact of growth temperature on ultrathin MoSe2 films grown on a Si(111) substrate using molecular beam epitaxy. The growth in the temperature range of 450 to 550 °C is explored. The growth temperature of 500 °C is found to be optimum for crystalline and uniform MoSe2 films. The quality of the grown films is thoroughly examined using techniques such as reflection high-energy electron diffraction, atomic force microscopy, and Raman spectroscopy. X-ray diffraction analysis reveals the presence of only the (002) family of planes, indicating growth along the c-axis of the substrate. X-ray photoelectron spectroscopy is employed to assess the elemental composition, and the results show a nearly stoichiometric composition of the film grown at 500 °C. A peak at 1.57 eV is observed in photoluminescence spectra for the sample grown at 500 °C, corresponding to the band gap of a few-layer MoSe2. The average grain size of the as-grown film (at 500 °C) is approximately 70 nm. Additionally, we conducted annealing experiments in a low-Se environment, which led to an enhancement in the grain size of the MoSe2 film, ranging from 66 to 135 nm. These results on the Si(111) substrate are a significant contribution to this work.