WS₂ Nanotube Transistor for Photodetection and Optoelectronic Memory Applications

Nanotube and nanowire transistors hold great promises for future electronic and optoelectronic devices owing to their downscaling possibilities. In this work, a single multi-walled tungsten disulfide (WS₂) nanotube is utilized as the channel of a back-gated field-effect transistor. The device exhibits a p-type behavior in ambient conditions, with a hole mobility µ_p ≈  1.4 cm²V^-1s^-1 and a subthreshold swing SS ≈ 10 V dec^-1. Current-voltage characterization at different temperatures reveals that the device presents two slightly different asymmetric Schottky barriers at drain and source contacts. Self-powered photoconduction driven by the photovoltaic effect is demonstrated, and a photoresponsivity R ≈ 10 mAW^-1 at 2 V drain bias and room temperature. Moreover, the transistor is tested for data storage applications. A two-state memory is reported, where positive and negative gate pulses drive the switching between two different current states, separated by a window of 130%. Finally, gate and light pulses are combined to demonstrate an optoelectronic memory with four well-separated states. The results herein presented are promising for data storage, Boolean logic, and neural network applications.