Multi-Layer Palladium Diselenide as a Contact Material for Two-Dimensional Tungsten Diselenide Field-Effect Transistors

Abstract

Tungsten diselenide (WSe2) has emerged as a promising ambipolar semiconductor material for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band gap, high carrier mobility, and remarkable on–off ratio. However, engineering the contacts to WSe2 remains an issue, and high contact barriers prevent the utilization of the full performance in electronic applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or hole injection and consequently pin the threshold voltage to either conduction or valence band. This would be the way to achieve complementary metal–oxide–semiconductor devices without doping of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material. This consequently yields high-performance p-type WSe2 devices with PdSe2 van der Waals contacts. Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2 under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding pure p-type operation of the devices.

All van der Waals Semiconducting PtSe2 Field Effect Transistors with Low Contact Resistance Graphite Electrodes

“…Contact resistance of the graphite/PtSe 2 interface was estimated with three independent approaches: in operando KPFM, − TLM, and a direct fitting of the I D ( V G ) curves with a Y function-based model. , In addition, an SBH was estimated from the temperature-dependent transport measurements, ,, indicating a low barrier at low carrier concentration density ( n 2D ) and essentially barrier-free operation at higher n 2D .…”

“…KPFM has emerged as a powerful approach to image the electrical potential distribution along the FET channel during operation. − It provides a direct measure for the source and drain contact resistances independently of each other by tracking the contact potential difference voltage ( V CPD ) profiles across the device active area. For our devices, the in operando measurements were done in a frequency modulation regime (FM-KPFM).…”