Lab-grown crystal contacts cut nanoscale transistor resistance

In transistors with 50 nm channels, the metal contact can be as important as the semiconductor beneath it. At the Shanghai Institute of Technical Physics, a team led by Chu Junhao has now grown single-crystal metal contacts directly on two-dimensional semiconductors, reaching contact resistances as low as 36 Ω·μm in n-type devices. The work was published in Science on Aug. 27, 2026.

The process is called Step-Eva. Instead of depositing metal continuously, researchers apply an atomic-scale dose and then wait through a prolonged stabilization pause, repeating the cycle. That pause lets atoms diffuse across the surface and merge into larger ordered domains, while suppressing the disordered nucleation that conventional evaporation can produce. The result is a metal film with long-range crystal order and a cleaner interface with the semiconductor.

The team reports that the approach works with bismuth, silver, indium, gold and palladium. The resulting contacts showed strongly suppressed Fermi-level pinning and contact resistances as low as 36 Ω·μm for n-type transistors and 145 Ω·μm for p-type transistors. Devices with channels scaled to 50 nm produced on-state currents above 1.1 mA μm⁻¹.

And so what, concretely? For researchers building smaller 2D transistors, Step-Eva offers a way to remove part of the resistance added by the metal connection rather than focusing only on improving the semiconductor. That could help future devices preserve electrical conduction as their dimensions shrink and support denser integration, although the evidence so far comes from laboratory devices rather than a production process or commercial chip.

The researchers also report on/off current ratios exceeding 10¹⁰ for both n-type and p-type transistors, along with dimensional scalability, continuous conduction at ultrathin thicknesses and enhanced thermal stability. Those properties make the contacts a possible materials foundation for energy-efficient electronic and optoelectronic systems. The reported figures remain the team’s results; no manufacturing line or deployed product is reported.