Liquid Metal 2D Printing Technique May Pave Way for Flexible Electronics

Computer chips could be thinner and faster. Credit: RMIT University

A new method using liquid metals to produce integrated circuits that are only atoms in thickness could pave the way for the next big advance in electronics.

The process allows the production of large wafers approximately 1.5 nm in depth (by comparison a sheet of paper measures 100,000 nm in thickness).

Other methods are unreliable in terms of quality and difficulty to expand, and function only at extremely high temperatures of 550 degrees or more.

Renowned Professor Kourosh Kalantar-zadeh, from the School of Engineering at RMIT University in Melbourne, Australia, led the project, which also included colleagues from RMIT and researchers from CSIRO, Monash University, North Carolina State University and the University of California.

He said the electronics sector had hit a hurdle.

The fundamental technology of car engines has not progressed since 1920 and now the same is happening to electronics. Mobile phones and computers are no more powerful than five years ago. That is why this new 2D printing technique is so important -- creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costs. It will allow for the next revolution in electronics.

Kourosh Kalantar-zadeh, Professor, RMIT University

Benjamin Carey, a researcher with RMIT and the CSIRO, said developing electronic wafers just atoms thick could surmount the limitations of existing chip production.

It could also create materials that were highly bendable, opening doors for the creation of flexible electronics.

However, 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. Our solution is to use the metals gallium and indium, which have a low melting point. These metals produce an atomically thin layer of oxide on their surface that naturally protects them. It is this thin oxide which we use in our fabrication method. By rolling the liquid metal, the oxide layer can be transferred on to an electronic wafer, which is then sulphurised. The surface of the wafer can be pre-treated to form individual transistors. We have used this novel method to create transistors and photo-detectors of very high gain and very high fabrication reliability in large scale.     

Benjamin Carey, Researcher, RMIT University

The research paper outlining the new method, “Wafer Scale Two Dimensional Semiconductors from Printed Oxide Skin of Liquid Metals”, has been published in the Nature Communications journal.

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