Liquid metal prints fast transistors express
An ordinary transistor in a phone is made in a vacuum chamber, where atoms are deposited layer by layer. Expensive and slow. But indium oxide can be printed like ink — from a drop of liquid metal that, in air, coats itself with a thin oxide film.
The authors took indium, melted it, and rolled it over a substrate at 250 degrees. The result was a polycrystalline layer only 5 nanometers thick — a thousand times thinner than a human hair. Its grains are large and span the entire thickness, so electrons move almost without obstacles.
The transistor built on this film works stably: after 10,000 on-off cycles, its characteristics did not degrade. And if you add a hafnium oxide insulator, the mobility stays high—107 cm²/V·s — while leakage current is minuscule. From such transistors, the team built an inverter, a basic logic element, and it amplifies the signal by a factor of 69.8.
Printing oxide semiconductors from liquid metal is like cooking on a skillet instead of molecular gastronomy: simpler, faster, and almost as tasty. The next step is to shrink the transistors and test them in real circuits.
Original abstract
as written by the authors arXiv:2604.06656
Oxide semiconductors have emerged as common channel materials in transistors and hold promise for next-generation electronics, yet achieving high mobility typically requires costly vacuum-based techniques. Here, ultrathin (5-nm) indium native oxide (InOx) prepared by ambient-air liquid-metal printing (LMP) at low temperature (250 {\deg}C), is applied as semiconducting channel in field-effect transistor (FET). The resulting InOx is found to be polycrystalline with large lateral grains that extend vertically throughout the film thickness. InOx FETs in a transfer length method (TLM) configuration demonstrate a high conductivity mobility (uCON) of 125 cm2 V-1 s-1, with systematic analysis of contact resistance confirming potential for channel length scaling. Integration with atomic-layer-deposited (ALD) gate dielectrics further reveals excellent compatibility, for instance, InOx FET integrated with HfO2 exhibits a high field-effect mobility (uFE) of 107 cm2 V-1 s-1, an on/off current ratio (ION/IOFF) of >107, a subthreshold swing (SS) of 204 mV dec-1, a gate leakage of <10-6 A cm-2, while maintaining stable performance over 104 endurance cycles without degradation. Post-fabrication oxygen-plasma treatment is applied to achieve enhancement-mode operation and a depletion-load inverter is demonstrated, exhibiting a voltage gain of 69.8 V/V. These results demonstrate the great potential of LMP InOx as semiconducting channel in high-performance and power-efficient transistors for next-generation oxide electronics.
An indium oxide film just 5 nanometers thick is transparent to the eye but conducts electricity — which is why such materials are used in touchscreens.
In the series 'Westworld,' robots are covered with thin films that are printed on the spot — similar to this technology, but for electronics.