UNIST Develops Inorganic Semiconductor Thin Film with Enhanced Flexibility and Durability
Demonstrated through the development of a monitoring device for Parkinson's disease patients
Manufacturable via inexpensive solution process, easy to commercialize


A research team led by Professors Jae-Sung Son, Moon-Ki Choi, and Joo-Young Kim of the Department of Materials Science and Engineering at Ulsan National University of Science and Technology (UNIST) succeeded in synthesizing silver sulfide (Ag2S) inorganic semiconductor thin films using an inexpensive solution process.

The performance of inorganic semiconductor thin films was also demonstrated by applying resistive random-access memory (RRAM) fabricated from the synthesized thin films to a monitoring device for Parkinson's disease patients. When the developed device is attached to a patient's body, it can detect movement abnormalities such as muscle spasms.

The silver sulfide inorganic semiconductor thin film developed by Professor Son's team exhibits semiconductor properties while also being highly flexible. Existing inorganic semiconductor materials are composed of ionic bonds and are easily broken, but the silver sulfide thin film developed this time has an elongation strain of 15%.

"Inorganic semiconductor materials have superior thermal and chemical stability compared to organic compound semiconductor materials, so they can be used in flexible electronic devices capable of stable operation even in high-temperature and high-humidity environments," explained Seung-Ki Cho, a postdoctoral researcher at Yonsei University's KIURI Research Group.

In particular, unlike existing methods, the newly developed inorganic semiconductor thin film can be manufactured using an inexpensive low-temperature solution process, making it advantageous for commercialization. The method involves rotating a solution containing inorganic semiconductor particles and a solvent over a substrate to apply a uniform coating. The solvent is then removed by evaporation.

"Existing production methods that apply high temperature and high pressure to raw materials are expensive to produce thin films, and other material layers that make up the memory device cannot withstand high temperature and high pressure, making it difficult to apply them directly to device fabrication," explained Cho So-young, a master's student in the Department of Materials Science and Engineering at UNIST.

In addition, the research team used this to develop the world's first 'stretchable thin-film silver sulfide-based resistive memory semiconductor'. This memory semiconductor device demonstrated a high on/off current ratio difference and operational durability, making it suitable for use in the development of adhesive health monitoring devices.

Yang Woo-jeong, a researcher in the integrated master's and doctoral program at the Department of Materials Science and Engineering at UNIST, explained, “We developed a patch-type device to monitor Parkinson's disease patients by combining stretchable RRAM with a motion sensor,” adding, “It is also possible to fabricate large-area matrix devices by using a touch sensor.”

Meanwhile, this research was published online in Advanced Materials on Friday, April 30, and is awaiting publication after being selected as a cover article. The research was supported by the National Research Foundation of Korea’s Future Materials Discovery Program and the Challenge Materials Technology Development Program.