Nonlinear Photoelectric Properties by Strained MoS2 and SnO2 Core-Shell Nanotubes for Flexible Visible Light Photodetectors

A new type of coaxial hetero-structured MoS2/SnO2 nanotube (MS-NT) array is rationally designed for flexible visible light photodetector. Herein, a suitable solution for fabricating MS-NT comprising SnO2 with controlled thickness and strain is proposed. The thickness of SnO2 deposited on MoS2 nanotubes are delicately manipulated by adjusting atomic layer deposition (ALD) cycles, which cause the internal tensile strain of the hybrid nanotubes. The photocurrent of the MS-NT-based photodetector exhibits high photoresponsivity values of 198.4 mA W-1 and external quantum efficiency of 0.78%. In the analysis, a linear correlation between the excitation power and the photocurrent extracted from the MNT-based devices is discerned. At the same time, a superlinearity of photocurrent in the MS-NT arrays-based device is found. Density functional theory calculations are adopted to unveil the strong correlation between the strain, bandgap, and photocurrent of the MS-NT, which is a decisive factor for understanding the experimental evidences. The detailed mechanism for enhance photoresponsivity is further suggested for the strain-tailored MS-NT arrays-based device. Such peculiar properties are expected to open a new chapter in the era of smart optical devices that require low driving voltage and high power efficiency.