Multi-carrier transport in ZrTe5 film

TL;DR

This study investigates the thickness-dependent transport properties of ZrTe5 films, revealing multi-carrier behavior, a carrier type transition at a critical thickness, and the importance of encapsulation for device quality.

Contribution

It provides a detailed analysis of multi-carrier transport in ZrTe5 films and identifies the transition from n-type to p-type carriers around 40 nm thickness.

Findings

Carrier type changes from n-type to p-type at ~40 nm thickness.

Multi-carrier transport is demonstrated through SdH oscillations and Hall measurements.

Encapsulation improves the device quality of ZrTe5 films.

Abstract

The single layer of Zirconium pentatelluride (ZrTe5) has been predicted to be a large-gap two-dimensional (2D) topological insulator, which has attracted particular attention in the topological phase transitions and potential device application. Here we investigated the transport properties in ZrTe5 films with the dependence of thickness from a few nm to several hundred nm. We find that the temperature of the resistivity anomaly's peak (Tp) is inclining to increase as the thickness decreases, and around a critical thickness of ~40 nm, the dominating carriers in the films change from n-type to p-type. With comprehensive studying of the Shubnikov-de Hass (SdH) oscillations and Hall resistance at variable temperatures, we demonstrate the multi-carrier transport instinct in the thin films. We extract the carrier densities and mobilities of two majority carriers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry's phase {\pi}, while the hole carriers may originate from the surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate ZrTe5 film in the inert or vacuum environment to make a substantial improvement in the device quality.