Environmental effects on the electrical characteristics of back-gated WSe2 field effect transistors

TL;DR

This study investigates how environmental factors like polymer coating, pressure, and temperature influence the electrical behavior of monolayer WSe2 back-gated transistors, revealing tunable conductivity, contact properties, and photoresponse characteristics.

Contribution

It provides new insights into environmental effects on WSe2 transistors, including conductivity switching, Schottky barrier characterization, and photoresponse performance.

Findings

Polymer removal or pressure reduction switches device from p- to n-type.

Measured a gate-tunable Schottky barrier of 60 meV.

Achieved a photoresponsivity of 0.5 AW^-1 at 700 nm.

Abstract

We study the effect of polymer coating, pressure and temperature on the electrical characteristics of monolayer WSe2 back-gated transistors with quasi-ohmic Ni/Au contacts. We find that the removal of a layer of poly(methyl methacrylate) or decreasing the pressure change the device conductivity from p to n-type. We study the current-voltage characteristics as a function of the temperature and measure a gate-tunable Schottky barrier at the contacts with a height of 60 meV in flat-band condition. We report and discuss a change in the mobility and the subthreshold slope observed with increasing temperature. Finally, we estimate the trap density at the WSe2/SiO2 interface and study the spectral photoresponse of the device, achieving a responsivity of 0.5 AW^-1 at 700 nm wavelength and 0.37 mWcm^-2 optical power.