Photo-responsive transistors of CVD grown single-layer MoS₂ and its nanoscale optical characteristics

The single-layer and multi-layers of MoS₂ were grown using the chemical vapor deposition (CVD) method. The structural properties of the MoS₂ were investigated through X-ray photoelectron spectroscopy (XPS). The optical characteristics in nanoscale of the MoS₂ were determined from the analysis of Raman and photoluminescence (PL) spectra using a high-resolution laser confocal microscope (LCM). Thin-film-transistors (TFTs) using a single-layer MoS₂ were fabricated, and the photo-responsive current-voltage (I–V) characteristics of the TFTs were measured with varying intensities of incident light. We observed the increase of both the photo-current and mobility with increasing the intensity of incident light. This is due to the contribution of photo-induced charge carriers from the valance band and trap states. The increasing rate of the photo-current of the TFTs with gate bias (i.e. on state) was considerably higher than that in off state, indicating the gate controlled photo-sensitive transistor.