Controlled Fabrication of Metallic MoO2 Nanosheets towards High‐Performance p‐Type 2D Transistors

Two‐dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) are extensively employed as channel materials in advanced electronic devices. The electrical contacts between electrodes and 2D semiconductors play a crucial role in the development of high‐performance transistors. While numerous strategies for electrode interface engineering have been proposed to enhance the performance of n‐type 2D transistors, upgrading p‐type ones in a similar manner remains a challenge. In this work, significant improvements in a p‐type WSe2 transistor are demonstrated by utilizing metallic MoO2 nanosheets as the electrode contact, which are controllably fabricated through physical vapor deposition and subsequent annealing. The MoO2 nanosheets exhibit an exceptional electrical conductivity of 8.4 × 104 S m‒1 and a breakdown current density of 3.3 × 106 A cm‒2. The work function of MoO2 nanosheets is determined to be ≈5.1 eV, making them suitable for contacting p‐type 2D semiconductors. Employing MoO2 nanosheets as the electrode contact in WSe2 transistors results in a notable increase in the field‐effect mobility to 92.0 cm2 V‒1 s‒1, which is one order of magnitude higher than the counterpart devices with conventional electrodes. This study not only introduces an intriguing 2D metal oxide to improve the electrical contact in p‐type 2D transistors, but also offers an effective approach to fabricating all‐2D devices. Through physical vapor deposition and postannealing, thin MoO3 nanosheets are completely converted into MoO2 with excellent crystal quality, which exhibits an exceptional electrical conductivity of 8.4 × 104 S m‒1. Using MoO2 nanosheets as the contact electrode for p‐type WSe2 field‐effect transistors can markedly enhance the transport property with a carrier mobility of up to 92.0 cm2 V‒1 s‒1.