A stepwise metal deposition technique could improve nanoscale transistor performance by creating cleaner contacts, lowering resistance and supporting more efficient future electronics.
Researchers at the Chinese Academy of Sciences have developed Step-Eva, a stepwise evaporation technique designed to create high-quality metal contacts for increasingly small transistors. The approach could help overcome one of the major barriers to continued miniaturisation: high contact resistance at metal–semiconductor interfaces.
As transistor dimensions shrink, imperfections in metal contacts can obstruct the movement of charge carriers, reducing device efficiency and limiting performance. Step-Eva tackles this problem by dividing metal deposition into repeated cycles of atomic-scale deposition followed by a stabilisation period. This allows atoms to settle and form a more ordered structure before the next layer is added.
The researchers report that the technique can produce single-crystal metal contacts with cleaner interfaces and more uniform electrical properties. It has been demonstrated with metals including silver, indium, gold and palladium, indicating that the approach could be applicable across a range of materials.
Tests on two-dimensional semiconductor devices showed particularly promising results. Both n-type and p-type transistors achieved on/off current ratios exceeding 10¹⁰, while devices with channel lengths scaled to 50 nanometres delivered on-state currents above 1.1 mA µm⁻¹.
Contact resistance was reported at approximately 36 Ω µm for n-type devices and 145 Ω µm for p-type devices, demonstrating efficient carrier injection and transport at nanoscale dimensions.
The researchers say the single-crystal contacts also maintain electrical conductivity at extremely small thicknesses and show improved thermal stability. These characteristics could support higher device density and more energy-efficient electronic and optoelectronic systems.
While further work is needed to establish large-scale manufacturing, the findings suggest that controlling metal growth at the atomic level could provide a practical route towards smaller, faster and more efficient transistor technologies.
