Atomically sharp heteroepitaxial Hf2C edge contacts enabling barrier-free carrier injection in 2D HfSe2 semiconducting channels

Achieving high-quality source/drain contacts in two-dimensional (2D) semiconductors remains challenging due to Fermi-level pinning induced by metal-induced gap states (MIGS). Here, we demonstrate an atomically sharp Hf₂C/HfSe₂ edge contact formed via a laterally directed chemical conversion, driven by catalyst-assisted hydrodeselenization and carbonization under epitaxial alignment. Classical and ab initio molecular dynamics elucidate the atomistic mechanism of heteroepitaxial interface formation. Scanning tunneling microscopy and spectroscopy measurements confirm suppressed MIGS at the heteroepitaxial interface, indicating an electronically transparent junction. Electrical measurements reveal a near-zero Schottky barrier height ( ≈ 5 meV) and reduced contact resistance ( ≈ 475 Ω·μm) when compared with previously reported 2D edge-contact systems. When co-integrated with a van der Waals-integrated native high-κ HfO₂ gate dielectric within a single HfSe₂ channel, the devices exhibit a subthreshold swing of 62 mV/dec and on-state current density of 920 μA/μm. This integrated platform establishes a scalable design framework that couples contact and gate-stack engineering for next-generation 2D logic technologies.