Morphological, optical and photovoltaic characteristics of MoSe₂/SiO_x/Si heterojunctions

This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe₂ layers grown by chemical vapour deposition (CVD), using MoO₃ and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe₂ layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe₂ layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe₂/SiO_x/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiO_x/MoSe₂ interface. A photovoltaic effect was observed with a short circuit current density (J_sc), open circuit voltage (V_OC) and efficiency of -0.80 mA/cm², 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe₂ with improved photovoltaic response.