Connecting with Atoms

2D semiconductors are a new class of advanced materials with outstanding properties attractive for many types of applications in electronics, flexible optoelectronics and quantum technology. However, realising these applications have not been easy, and one of the main challenges has been the lack of a proper contact strategy. A*STAR scientists in collaboration with Prof. Manish Chhowalla’s team from Cambridge and Prof. Ricky Ang’s team from SUTD have finally succeeded in solving a longstanding problem in the field of 2D semiconductors: demonstrating a viable contact strategy operable at low temperatures.

Low contact resistances are crucial for electrical charges carrying useful information to flow seamlessly through the materials. High quality contacts are even more critical in the field of quantum technology, where devices are frequently operated at temperatures colder than outer space. Till now, such contacts have proved elusive as conventional techniques lead to collateral damage to material surface. While acceptable in bulk materials, such damage can be catastrophic for 2D semiconductors composed of a single layer of atoms, as the material surface is also the body.

In the Institute of Materials Research and Engineering, Dr. Johnson Goh's team and collaborators have unlocked the potential of indium alloys to form high quality contacts to 2D tungsten disulfide. They demonstrated devices working at -270 oC with record low contact resistances and device performances up to a thousand times better than previously reported. To understand the underlying physics, the team relied on complex calculations performed at the National Supercomputing Centre. These calculations shed new insights into the nature of low temperature charge injection and transport in atomically thin semiconductors. Their findings are an important step towards the design of next generation devices based on 2D semiconductors.

Reference:
C. S. Lau et al., "Quantum Transport in Two-Dimensional WS2 with High-Efficiency Carrier Injection through Indium Alloy Contacts", ACS Nano 14(10), 13700-13708 (2020)

Link to online version of paper in ACS Nano.