Universal low-temperature Ohmic contacts for quantum transport in transition metal dichalcogenides

TL;DR

This paper presents a universal method to create low-temperature Ohmic contacts in TMDC devices, significantly improving their electrical performance and enabling advanced quantum transport studies.

Contribution

The authors develop a versatile contact fabrication technique applicable to various TMDCs, achieving low resistance and high mobility at cryogenic temperatures.

Findings

Achieved low contact resistance at 2 K

Demonstrated high field-effect mobilities up to 16000 cm2/V s

Observed prominent Shubnikov-de Haas oscillations

Abstract

Low carrier mobility and high electrical contact resistance are two major obstacles prohibiting explorations of quantum transport in TMDCs. Here, we demonstrate an effective method to establish low-temperature Ohmic contacts in boron nitride encapsulated TMDC devices based on selective etching and conventional electron-beam evaporation of metal electrodes. This method works for most extensively studied TMDCs in recent years, including MoS2, MoSe2, WSe2, WS2, and 2H-MoTe2. Low electrical contact resistance is achieved at 2 K. All of the few-layer TMDC devices studied show excellent performance with remarkably improved field-effect mobilities ranging from 2300 cm2/V s to 16000 cm2/V s, as verified by the high carrier mobilities extracted from Hall effect measurements. Moreover, both high-mobility n-type and p-type TMDC channels can be realized by simply using appropriate contact metals. Prominent Shubnikov-de Haas oscillations have been observed and investigated in these high-quality TMDC devices.