Single-step process simplifies development of new materials

The team at the University of Texas at Austin’s Cockrell School of Engineering is using microwave energy to assemble atoms into thin films and is growing them directly onto a substrate at significantly low temperatures.

Results of the team’s research, conducted under the supervision of Prof Arumugam Manthiram of the Texas Materials Institute and the Department of Mechanical Engineering and Prof Ali Yilmaz of the Department of Electrical and Computer Engineering, were published in the 19 December issue of Scientific Reports.

‘Lowering the temperature at which thin films of relevant materials can be grown is one of the key focus areas of our research,’ said Reeja Jayan, postdoctoral fellow at the University of Texas at Austin and one of the lead authors of the paper. ‘With our microwave process, we could bring down temperatures to the level that enables us to grow materials on heat-sensitive surfaces, such as plastics, without damaging them.’

The conventional methods for growing thin films typically require temperatures of more than 450ºC for several hours and a cumbersome multi-step process.

With the new method, thin films can now be grown at temperatures as low as 150ºC in less than 30 minutes, in a single-step process, by using microwaves.

‘With this new method, the process of thin-film growth is made simple, wherein a solution containing the atoms of the desired material, together with the substrate, when exposed to microwaves can result in controlled film growth,’ said Manthiram in a statement. ‘Applications that could utilise this process include developing thin-film batteries and solar cells that could be integrated into various devices such as cell phones and tablets.’

The team coats a conducting layer — similar to a metal — over the substrate, which serves like an antenna to attract the microwaves.

The energy from the microwaves then coerces atoms from the solution to self-assemble into uniform thin films on the substrate.

The local heating generated by the interaction between the microwaves and the metal layer serves to fuse the thin films to the substrate — an interaction so powerful it makes the films strongly adhere to the substrate.

As part of the research, a computational model of the process was developed by the team, which helps better understand the physics behind the microwave interaction phenomena and provides them with predictive guidelines that can significantly reduce the number of experiments needed for future research.

The team at the University of Texas at Austin has successfully demonstrated the assembly of titanium oxide thin films at low temperatures and is currently working towards the assembly of thin films in a variety of materials.