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Stanford’s Breakthrough New Manufacturing Technique for Ultrathin, Flexible Electronics

A diagram of the transfer process of a 2D semiconductor with nanopatterned contacts (left) and a photo of a flexible transparent substrate with the transferred structure (right). Credits: Victoria Chen / Alwin Daus / Pop Lab

The long-sought future of wearable flexible electronics has proven to be elusive, but researchers at Stanford University say they have made a breakthrough.

Ultra-thin and flexible computer circuits have been an engineering goal for many years, but technical hurdles have hampered the degree of miniaturization required to achieve high performance. Researchers at Stanford University have now invented a manufacturing technique that produces flexible, atomically thin transistors that are less than 100 nanometers in length. This is a fraction of what it was before. Details of this technique can be found in a paper published today (June 17, 2021). Nature Electronics..

Researchers said that with progress, so-called “flextronics” would come closer to reality. Flexible electronics promise a bendable, moldable yet energy efficient computer circuit. This computer circuit can be worn or transplanted into the human body to perform a myriad of health-related tasks. In addition, the upcoming “Internet of Things,” where almost every device in our lives is integrated and interconnected with flexible electronics, should benefit from Flextronics as well.

Technical problem

Among the materials suitable for flexible electronics, two-dimensional (2D) semiconductors are better candidates than traditional silicon and organic materials because of their excellent mechanical and electrical properties even at the nanoscale. ..

The engineering challenge to date has been that flexible plastic substrates require a process that consumes a lot of heat to form these nearly impossiblely thin devices. These flexible materials simply melt and decompose during the manufacturing process.

According to Eric Pop, a professor of electrical engineering at Stanford University, and Alwin Daus, a postdoctoral fellow in Pop’s lab who developed the technology, the solution starts with an inflexible base substrate and is step-by-step. That is.

On a glass-coated silicon solid slab, Pop and Daus form an atomic thin film of 2D semiconductor molybdenum disulfide (MoS).2) It is covered with a small nano-patterned gold electrode. Because this step is performed on a traditional silicon substrate, the dimensions of nanoscale transistors can be patterned with existing advanced patterning techniques, achieving resolutions not possible with flexible plastic substrates.

A layering technique known as chemical vapor deposition (CVD) grows MoS films.2 One layer of atoms at a time. The resulting film is only 3 atoms thick, but requires temperatures up to 850 C (1500 F and above) to function. By comparison, flexible substrates made of thin plastic polyimide lost their shape around 360 ° C (680 ° F) long ago and were completely decomposed at high temperatures.

Researchers at Stanford University can apply flexible materials without damage by first patterning and forming these key components on hard silicon and then cooling. Simply soaking in deionized water will remove the entire device stack and transfer it completely to the flexible polyimide.

After some additional manufacturing steps, the result is a flexible transistor that can perform several times better than previously manufactured with atomically thin semiconductors. Researchers say that the entire circuit can be built and then transferred to flexible materials, but the specific complexity associated with subsequent layers facilitates these additional steps after transfer.

“Ultimately, the overall thickness of the structure, including the flexible polyimide, is only 5 microns,” said Pop, senior author of this treatise. “It’s about a tenth of human hair.”

Although the technological achievements of manufacturing nanoscale transistors from flexible materials are remarkable in their own right, researchers have described the device as “high performance.” This means that it can handle large currents while operating at low voltages. , When required for low power consumption.

“There are several benefits to this downscaling,” said Daus, the first author of this treatise. “Of course, you can install more transistors in a particular footprint, but you can also carry higher currents at lower voltages, which means faster with less power consumption.”

Gold metal contacts, on the other hand, dissipate and dissipate the heat generated by the transistors during use. This heat can endanger flexible polyimides.

Promising future

After completing the prototype and patent application, Daus and Pop moved on to the next challenge of improving the device. They built a similar transistor using two other atomically thin semiconductors (MoSe).2 And WSe2) Demonstrate the wide applicability of the technology.

Meanwhile, Daus said he is considering integrating wireless circuits with the device. This will allow future variations to communicate wirelessly with the outside world. This is another major leap towards the feasibility of flextronics, especially embedded in the human body or deeply integrated into other devices. You are connected to the Internet of Things.

“This is more than a promising production technology. It offers flexibility, density, high performance, and low power at the same time,” Pop said. “I hope this work will bring technology forward at several levels.”

Reference: June 17, 2021 Nature Electronics..
DOI: 10.1038 / s41928-021-00598-6

Co-authors include postdoctoral researchers Sam Vaziri and Kevin Brenner, postdoctoral candidates Victoria Chen, Çağıl Köroğlu, Ryan Grady, Connor Bailey and Kirstin Schauble, and research scientist Hye Ryoung Lee.

This study was funded by the Early Postdoctoral Mobility Fellowship of the Swiss National Science Foundation, the Beijing Institute for Joint Innovation, the National Science Foundation, and the Stanford System X Alliance.



Stanford’s Breakthrough New Manufacturing Technique for Ultrathin, Flexible Electronics Source link Stanford’s Breakthrough New Manufacturing Technique for Ultrathin, Flexible Electronics

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