Metal-Insulator transition and Charge Transport Mechanisms in SnSe$_2$ Field-Effect Transistor

TL;DR

This study observes a metal-insulator transition in SnSe$_2$ thin films, revealing how electrostatic doping and temperature influence charge transport mechanisms, with implications for optimizing 2D material-based electronic devices.

Contribution

It provides the first detailed analysis of the metal-insulator transition and charge transport mechanisms in SnSe$_2$ FETs, highlighting the effects of electrostatic doping and temperature.

Findings

Metal-insulator transition observed at high doping levels.

Charge transport at low temperatures governed by 2D variable-range hopping.

Mobility limited by charged impurities at low T and electron-phonon scattering at high T.

Abstract

We report an observation of metal-insulator transition in a thin film of SnSe$_2$. The room-temperature carrier concentration of SnSe$_2$ film was increased by electrostatic doping to 1.14$\times$ 10$^{13}$ cm$^{-2}$. A crossover from insulating phase to metallic state was clearly observed. The low-temperature charge transport mechanism is governed by two-dimensional (2D) variable-range hopping. This mechanism is influenced by band bending and gap states introduced by selenium vacancies. At low temperatures, the mobility is primarily limited by charged impurities, while at higher temperatures, it follows a power-law dependence, $\mu = T^{-\gamma}$, indicating a dominance of electron-phonon scattering. The application of a gate field shifts the Fermi level toward the conduction band, and at sufficiently high temperatures, this drives the system into a metallic state. Our findings offer insights into the charge transport mechanisms in SnSe$_2$ FET, this understanding will allow for the optimization of other 2D materials for advanced electronic device applications.