Fermi Level Depinning in WSe ₂ Field‐Effect Transistors via a Van der Waals Interlayer of 2D Networks From 1D Carbon Nanotubes

ABSTRACT 2D layered semiconductors show great promise as channel materials for post‐Si electronic devices, and the interfaces they form are critical determining factors in device performance. In particular, the interface between 2D layered materials and metal contacts is highly problematic because of the Fermi‐level pinning (FLP) phenomenon. FLP results in a high Schottky barrier height (SBH), which hinders carrier transport and polarity modulation in devices. Here, we present a simple, scalable, solution‐processable contact‐engineering approach for the 2D layered material WSe 2 that involves inserting a van der Waals (vdW) interlayer of networked single‐walled carbon nanotubes (CNTs). The networked CNTs act as a pseudo‐2D layer that effectively separates the metal contacts from WSe 2 . Additionally, the bundled CNTs serve as an efficient electrical interlayer. In the Pd‐contacted case, the SBH with WSe 2 decreases from 357 meV to 46 meV upon insertion of the CNT interlayer, which enables efficient tunneling‐based carrier injection into the WSe2 channel, resulting in an improvement in the pinning factor from S = −0.021 to S = −0.42. This work demonstrates that a 2D vdW interlayer can be prepared through a solution process to mitigate FLP, thereby facilitating the large‐scale fabrication of device arrays and circuits based on 2D layered materials.