van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28792227.
- Also identified by DOI 10.1021/acs.nanolett.7b01817.
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Abstract
Because of the chemical inertness of two dimensional (2D) hexagonal-boron nitride (h-BN), few atomic-layer h-BN is often used to encapsulate air-sensitive 2D crystals such as black phosphorus (BP). However, the effects of h-BN on Schottky barrier height, doping, and contact resistance are not well-known. Here, we investigate these effects by fabricating h-BN encapsulated BP transistors with cobalt (Co) contacts. In sharp contrast to directly Co contacted p-type BP devices, we observe strong n-type conduction upon insertion of the h-BN at the Co/BP interface. First-principles calculations show that this difference arises from the much larger interface dipole at the Co/h-BN interface compared to the Co/BP interface, which reduces the work function of the Co/h-BN contact. The Co/h-BN contacts exhibit low contact resistances (∼4.5 kΩ) and are Schottky barrier-free. This allows us to probe high electron mobilities (4,200 cm<sup>2</sup>/(V s)) and observe insulator-metal transitions even under two-terminal measurement geometry.