South Korean Team Maps Charge Flow Across Seamless Semiconductor Interface

Researchers at KAIST and Sungkyunkwan University have demonstrated a way to move electrical current from a conductive region into a semiconducting region without crossing a conventional metal-semiconductor junction. The team, led by Professor Seungbum Hong at KAIST's Department of Materials Science and Engineering with collaborators at Sungkyunkwan University, created both regions within a single continuous sheet of platinum diselenide (PtSe₂), exploiting the material's thickness-dependent electronic behavior, thicker areas act as a semimetal, thinner areas as a semiconductor. Contact resistance at metal-semiconductor boundaries wastes power, generates heat, and limits performance gains from shrinking transistors. The problem is acute for two-dimensional semiconductors, which are atomically thin and easily damaged by conventional electrode deposition. The monolithic PtSe₂ structure avoids a physical break at the interface, giving charges a more direct path into the semiconductor. Using atomic force microscopy with in-plane current detection, the researchers mapped charge movement across the boundary at the nanometer scale. The images showed current continuing across the interface without deflection or blocking, the first direct experimental demonstration of uninterrupted charge transport across a monolithic semimetal-to-semiconductor interface, according to the authors. Applying an electric field to the semiconducting region also successfully modulated the current, confirming the structure can perform transistor switching. The work, published in the journal Matter, was supported by South Korea's Ministry of Science and ICT and the National Research Foundation of Korea. Challenges remain in reliability, circuit integration, and large-scale manufacturing, but the approach suggests a new strategy for building contacts and semiconductors from different regions of the same two-dimensional material.