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

• Growth of a single-layer and multi-layers of MoS2 using chemical vapor deposition method.
• Clear difference of nanoscale PL and Raman characteristics of a single-layer and tetra-layer MoS2 samples.
• Increase of photo-current and mobility of the single-layer MoS2 TFTs with increasing the optical power.

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.

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