Liquid metals create nanometre-thick ICs

Scientists are using liquid metals to create integrated circuits (ICs) that are merely atoms thick, opening the way for the production of large wafers around 1.5 nm in depth. A sheet of paper, by comparison, is 100,000 nm thick.

The project was led by Distinguished Professor Kourosh Kalantar-zadeh, from RMIT University, in collaboration with Australian and US colleagues. He said 2D printing will allow for “the next revolution in electronics”, noting that “creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costs”.

Unfortunately, other 2D printing techniques have so far proven unreliable in terms of quality, been difficult to scale up and function only at very high temperatures — 550°C or more.

“None of the current technologies are able to create homogenous surfaces of atomically thin semiconductors on large surface areas that are useful for the industrial-scale fabrication of chips,” said Benjamin Carey, a researcher at RMIT and CSIRO.

“Our solution is to use the metals gallium and indium, which have a low melting point.”

Writing in the journal Nature Communications, the researchers explained that these metals produce an atomically thin oxide layer on their surface that naturally protects them. It is this thin oxide which was used in their fabrication method.

“By rolling the liquid metal, the oxide layer can be transferred onto an electronic wafer, which is then sulfurised,” said Carey. “The surface of the wafer can be pretreated to form individual transistors.

“We have used this novel method to create transistors and photodetectors of very high gain and very high fabrication reliability in large scale.”

Carey said creating electronic wafers just atoms thick could overcome the limitations of current chip production. It could also produce materials that are extremely bendable, paving the way for flexible electronics.