The researchers at UNSW is extending their research on ultra-thin semiconductors is molybdenum disulphide (MoS2). The MoS2 for decades has shown great potential for its electronic properties. However, the researchers are trying to overcome Moore’s Law to resort to two-dimensional semiconductors.
Hurdles in Obtaining Very Large-Scale Two-Dimensional MoS2
However, obtaining very large-scale two-dimensional MoS2 without any grain boundaries has been proven to be a real challenge. Using any current large-scale deposition technologies, grain-boundary-free MoS2 which is essential for making ICs has yet been reached with acceptable maturity. However, now researchers at the School of Chemical Engineering, University of New South Wales (UNSW) have developed a method to eliminate such grain boundaries based on a new deposition approach.
“This unique capability was achieved with the help of gallium metal in its liquid state. Gallium is an amazing metal with a low melting point of only 29.8 °C. It means that at a normal office temperature it is solid, while it turns into a liquid when placed at the palm of someone’s hand. It is a melted metal, so its surface is atomically smooth. It is also a conventional metal which means that its surface provides a large number of free electrons for facilitating chemical reactions.” Ms Yifang Wang, the first author of the paper said.
“By bringing the sources of molybdenum and sulphur near the surface of gallium liquid metal, we were able to realize chemical reactions that form the molybdenum sulphur bonds to establish the desired MoS2. The formed two-dimensional material is templated onto an atomically smooth surface of gallium, so it is naturally nucleated and grain boundary-free. This means that by a second step annealing, we were able to obtain very large area MoS2 with no grain boundary. This is a very important step for scaling up this fascinating ultra-smooth semiconductor.” Prof Kourosh Kalantar-Zadeh, the leading author of the work said.
The researchers at UNSW are now planning to expand their methods of creating other two-dimensional semiconductors and dielectric materials in order to create a number of materials that can be used as different parts of transistors.