Hysteresis and Photoconductivity of Few-Layer ReSe2 Field Effect Transistors Enhanced by Air Pressure

This study reports the optoelectronic characterization of few-layer ReSe(2)field effect transistors at different pressures. The output curves reveal dominant n-type behavior and a low Schottky barrier at the metal contacts. The transfer curves show a significant hysteresis that can be exploited in memory devices with an order ofmagnitude memory window and good cycling. The devices are dramatically affected by air pressure; their conductance and mobility increase with the lowering pressure that desorbs electronegative air molecules from the surface of the material. The photoresponse under white super-continuum laser illumination reveals that the device exhibits positive photoconductivity (PPC) at ambient and low (approximate to 1 mbar) pressure and negative photoconductivity (NPC) in a higher vacuum (approximate to 10(-4) mbar). The transition from PPC to NPC can be explained by considering that the photoresponse is affected by molecule desorption, which yields PPC at higher pressure, and defect trapping of photogenerated carriers, which can dominate at lower pressures. The transient behavior of the device exposed to laser pulses shows a faster response and a higher photodetection efficiency at ambient pressure, with the highest signal-to-noise ratio at the valley of the transfer curve between p- and n-type conduction.

Automated summary

This study reports the optoelectronic characterization of few-layer ReSe2 field effect transistors at different pressures. The devices exhibit a dominant n-type behavior with low Schottky barrier and significant hysteresis. The conductance and mobility of the devices are affected by air pressure, increasing with lower pressure due to the desorption of electronegative air molecules. The photoresponse of the device changes from positive photoconductivity at higher pressure to negative photoconductivity at lower pressure, which can be explained by the desorption of molecules and the defect trapping of photogenerated carriers.