Paper 2D-FrM12
Reactivity of Metal Contacts with Monolayer Tungsten Disulfide

Friday, October 25, 2019, 12:00 pm, Room A215

Using two-dimensional transition metal dichalcogenides (TMD) for electronics, optoelectronics, and catalysis often requires integration with a metal, motivating fundamental studies of metal-TMD interactions. We previously published predictions on the reactivity of metals with tungsten disulfide based on thermodynamics. [1] Our current work employs an easy approach to test these predictions on reactivity of metal contacts with monolayer (1L) WS₂ using Raman spectroscopy performed through the backside of the contact. Au, Cu, Pd, Al, and Ti were deposited by electron beam evaporation onto 1L WS₂ grown on a sapphire substrate and capped with a thin film of silica to avoid agglomeration of the metal during annealing. Samples were annealed at 100, 200, and 300 °C under Ar for 1 hour. The results from Raman spectroscopy are in excellent agreement with the predictions from thermodynamics. Au, Cu, and Pd did not react with 1L WS₂ upon deposition or annealing. Reaction of Al with 1L WS₂ occurred upon annealing, while Ti reacted upon deposition, as indicated by loss of the characteristic peaks in the Raman spectrum for WS₂. We will also describe interesting changes in the Raman spectrum for WS₂ from Au/WS₂ samples and present transmission electron microscopy of these samples.

[1] Yitian Zeng, Anna C. Domask, Suzanne E. Mohney, Condensed phase diagrams for the metal–W–S systems and their relevance for contacts to WS₂, Materials Science and Engineering: B, Volume 212, October 2016, Pages 78- 88: http://dx.doi.org/10.1016/j.mseb.2016.07.005.

The authors thank the National Science Foundation (DMR 1410334) for their support of this project. Monolayer WS₂ was provided by The Pennsylvania State University Two-Dimensional Crystal Consortium – Materials Innovation Platform (2DCC-MIP) supported by NSF cooperative agreement DMR-1539916.