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BREAKING NEWS A New, Positive Approach Could Be the Key to Next-Generation, Transparent Electronics An RMIT University-led team has introduced ultrathin betatellurite to the 2D semiconducting material family, which provides an answer to the decades-long search for a high mobility p-type oxide. Researchers have sought a new class of electronics based on semiconducting oxides, whose optical transparency could enable these fully transparent electronics. These see-through devices could potentially be integrated in glass, flexible displays and in smart contact lenses – bringing to life futuristic devices that seem like the product of science fiction. Dr Torben Daeneke led the collaboration across three FLEET nodes. He said the research was a breakthrough. “This new, high-mobility p-type oxide fills a crucial gap in the materials spectrum to enable fast, transparent circuits.” The oxide-based semiconductors also provide a suite of other benefits, like their stability in the air, less-stringent purity requirements, low costs, and easy deposition. “In our advance, the missing link was finding the right, ‘positive’ approach,” Dr Daeneke said. There are two types of semiconducting materials: ‘n-type’ materials have abundant negatively charged electrons, while ‘p-type’ semiconductors possess positively charged holes. When complementary n-type and p-type materials stack together, it allows for electronic devices to be created, like diodes, rectifiers, and logic circuits. These materials are the building blocks of every computer and smartphone, which are crucial in contemporary living. This project was supported by the Australian Research Council and also by RMIT University’s Microscopy and Microanalysis Facility. It received funding from the McKenzie postdoctoral fellowship program from the University of Melbourne.
Above: A magnified image showing nano-thin sheets of the new type of ultra-efficient, flexible and printable piezoelectric material. Credit: RMIT University. Right: The new material could be used to develop devices that convert blood pressure into a power source for pacemakers. Credit: RMIT University.
Nano-Thin Piezoelectrics Advance Self-Powered Electronics RMIT researchers have discovered a new type of ultraefficient, nano-thin material that could advance self-powered electronics and even deliver pacemakers powered by heart beats. The flexible and printable piezoelectric material – able to convert mechanical pressure into electrical energy – is 100,000 times thinner than a human hair and 800% more efficient than other piezoelectrics based on similar non-toxic materials. Researchers believe it can be easily fabricated through a costeffective and commercially scalable method through the use of liquid metals. Dr Nasir Mahmood, who led the project, said the material was a major step towards realising the full potential of motiondriven, energy-harvesting devices. “Until now, the best performing nano-thin piezoelectrics have been based on lead, a toxic material that is not suitable for biomedical use.” “Our new material is based on non-toxic zinc oxide, which is also lightweight and compatible with silicon, making it easy to integrate into current electronics,” Dr Mahmood explained.
The RMIT team from left, Ali Zavabeti, Patjaree Aukarasereenont and Torben Daeneke with transparent electronics.
The optical transparency of the new materials could enable futuristic, flexible, transparent electronics. Credit: RMIT University.
The potential biomedical applications within the materials include internal biosensors and self-powering biotechnologies, including devices that convert blood pressure into a power source for pacemakers. The nano-thin piezoelectrics may also be used in the development of smart oscillation sensors to detect faults in infrastructure like buildings and bridges, especially in earthquake-prone regions. “It’s so efficient that all you need is a single 1.1 nanometre layer of our material to produce all the energy required for a fully self-powering nanodevice,” Dr Mahmood said.
A molten mixture of tellurium and selenium rolled over a surface deposits an atomically-thin sheet of beta-tellurite.
46 | JUNE 2021
Crystal structure of beta-tellurite showing charge density.
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The new material is produced using a liquid metal printing approach, which was entirely pioneered at RMIT. WWW.MATERIALSAUSTRALIA.COM.AU
