Two-dimensional (2D) materials* such as molybdenum-disulfide (MoS 2 ) are attracting much attention for future electronic and photonic applications ranging from high-performance computing to flexible and pervasive sensors and optoelectronics. But in order for their promise to be realized, scientists need to understand how the performance of devices made with 2D materials is affected by different kinds of metal electrical contacts.

Researchers in PML's Semiconductor & Dimensional Metrology Division, in collaboration with researchers from George Mason University, compared silver and titanium contacts on MoS 2 transistors to determine the influence of the metal–MoS 2 interface. A sophisticated suite of measurements (Raman spectroscopy, scanning electron microscopy and atomic force microscopy) was used to characterize the surface morphology and the interface between MoS 2 and the metals, the properties of which affect the device behavior. It was found that silver provides a much better electrical contact to MoS 2 than the widely used titanium, with the silver-contact devices having 60 times higher current when the device is in the "on" state. These results are another step towards the advanced manufacture of high-value products based on 2D materials.

*2D materials are only a single layer or atoms or molecules thick. The most familiar example is graphene, composed of one atomic layer of carbon atoms.

"Influence of Metal−MoS 2 Interface on MoS 2 Transistor Performance: Comparison of Ag and Ti Contacts," Hui Yuan, Guangjun Cheng, Lin You, Haitao Li, Hao Zhu, Wei Li, Joseph J. Kopanski, Yaw S. Obeng, Angela R. Hight Walker, David J. Gundlach, Curt A. Richter, Dimitris E. Ioannou, and Qiliang Li.

ACS Appl. Mater. Interfaces, Article ASAP. Publication Date (Web): [December 16, 2014]