One-Dimensional Edge Contacts to Two-Dimensional Transition-Metal Dichalcogenides: Uncovering the Role of Schottky-Barrier Anisotropy in Charge Transport across MoS2/Metal Interfaces

One-dimensional (1D) edge contacts to two-dimensional (2D) transition-metal dichalcogenides (TMDs), which offer unique features in the design of electronic devices, have recently gained attention. However, the physics of the Schottky barrier of the edge contacts and how exactly it differs from conventional top contacts is not well known. This paper presents a comprehensive ab initio density-functional-theory nonequilibrium green's function study of the electrical properties of edge contacts to 2D MoS2. It is observed that, due to the intrinsic terminated edge states, 1D edge contacts to MoS2 are pinned more strongly to a charge-neutrality level that lies closer to the valence band and yields p-type characteristics, which are in contrast to top contacts. This Schottky-barrier anisotropy allows edge contacts in MoS2 to outperform top contacts in p-type conduction, despite their atomically thin one-dimensional interfaces. Furthermore, the lower limits of contact resistance achievable by edge contacts to MoS2 are estimated. The role of doping, different edge terminations, and Schottky-barrier inhomogeneity in imperfect edge or hybrid contacts are analyzed to assess and provide design guidelines and conditions under which we can utilize edge contacts for various applications including complimentary field-effect transistor (FET) operation.

Automated summary

Edge contacts to 2D MoS2 exhibit stronger pinning to charge-neutrality level close to the valence band due to intrinsic terminated edge states, leading to p-type characteristics in contrast to top contacts. Despite being atomically thin one-dimensional interfaces, edge contacts in MoS2 outperform top contacts in p-type conduction.