Flexible material developed to enable tiny transistors

A research team led by UNSW Sydney has developed a tiny, transparent and flexible material to be used as a novel dielectric (insulator) component in transistors, which would enable these devices to shrink in size without compromising their function. Published in the journal Nature, the team’s research indicates the potential for large-scale production of a 2D field-effect transistor — a device used to control current in electronics.

A transistor is a small semiconductive device used as a switch for electronic signals, and an essential component of integrated circuits. All electronics, from torches to hearing aids to laptops, are made possible by various arrangements and interactions of transistors with other components like resistors and capacitors.

As transistors have become smaller and more powerful over time, so too have electronics. But there’s a scaling problem: developing more powerful future electronics will require transistors with sub-nanometre thickness — a size that conventional silicon semiconductors cannot reach.

“As microelectronic miniaturisation occurs, the materials currently being used are pushed to their limits because of energy loss and dissipation as signals pass from one transistor to the next,” said Professor Sean Li, UNSW Materials and Manufacturing Futures Institute (MMFI) Director and principal investigator on the new research.

“With such limits, there has been an enormous drive to radically innovate new materials and technologies to meet the insatiable demands of the global microelectronics market.”

The new material could help overcome the challenges of nanoscale silicon semiconductor production for dependable capacitance (electrical charge stored) and efficient switching behaviour. According to the researchers, this is one of the crucial bottlenecks to solve for the development of a new generation of futuristic electronic devices.

“Not only does it pave a critical pathway to overcome the fundamental limit of the current silicon semiconductor industry in miniaturisation, but it also fills a gap in semiconductor applications due to silicon’s opaque and rigid nature,” Li said. “Simultaneously, the elastic and slim nature could enable the accomplishment of flexible and transparent 2D electronics.”

MMFI engineers fabricated the transparent field-effect transistors using a freestanding single-crystal strontium titanate (STO) membrane as the gate dielectric. They discovered their new miniaturised devices matched the performance of current silicon-semiconductor field-effect transistors.

“The key innovation of this work is that we transformed conventional 3D bulk materials into a quasi-2D form without degrading its properties,” said Dr Jing-Kai Huang, lead author on the study. “This means it can be freely assembled, like Lego blocks, with other materials to create high-performance transistors for a variety of emerging and undiscovered applications.”

The MMFI academics drew on their diverse expertise to complete the work, with study co-author Dr Ji Zhang explaining that fabricating devices involves people from different fields. “Through MMFI, we have established connections with academics who are experts in the 2D electric device fields as well as the semiconductor industry,” Zhang said.

“The first project was to fabricate the freestanding STO and to study its electrical properties. As the project progressed, it evolved into fabricating 2D transistors using freestanding STO. With the help from the platform established by MMFI, we were able to work together to finish the project.”

The team is now working towards wafer-scale production; in other words, they hope to see whether the material can be used to build all the circuits for an entire computer on one chip. According to Huang, “Achieving this will enable us to fabricate more complex circuits with a density closer to commercial products. This is the crucial step to make our technology reach people.”

The researchers also say their development is a promising step towards a new era of electronics and local manufacturing resilience, with Huang claiming it serves as a chance for Australia to join and strengthen the global semiconductor supply chain.

The technology is currently protected by two Australian provisional patent applications, with MMFI and UNSW looking to commercialise the intellectual property and bring it to market. Li said the researchers are “currently fabricating logic circuits with the transistors”, while also “approaching several leading industries in the Asia–Pacific region to attract investment and establish a semiconductor manufacturing capability in NSW via industrialisation of this technology”.

Image caption: Researchers from the Materials and Manufacturing Futures Institute designed the material. Image credit: Robert Largent.

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