Self-Intercalation Metallization Enables Low-Resistance Contacts in ZrSe ₂ and HfSe ₂

Two-dimensional (2D) ZrSe₂ and HfSe₂ are promising channel candidates for postsilicon electronics due to their manufacturing-compatible "high-k: native oxides, yet the device performance is limited by high contact resistance. Here, we demonstrate a self-intercalation metallization strategy that drives a semiconductor-to-metal transition by insertion of excess Zr and Hf atoms into the van der Waals (vdW) gaps. This process expands the vdW gaps and introduces extra electron states that shift the Fermi level into the conduction band without lattice disruption. Devices incorporating these metallic buffers exhibit low Schottky barriers (∼27 meV), on/off ratios up to 10⁴, a >20× higher on-current, and an over 100× lower contact resistance than Au contacts. This work establishes a silicon-analogue low-barrier contact paradigm for Zr/Hf selenides and offers a general route for contact engineering in emerging 2D semiconductors via controlled self-intercalation.