Formation of Nickel After WS2 Hydrogen-Cracking Modifications

Wei-Tung Liu^1*, Hui-Ting Liu², Wan-Hsin Chen¹, Shu-Jui Chang², Kuan-Yu Chen¹, Chun-Liang Lin¹, Chenming Hu²

¹電子物理, 國立陽明交通大學, 新竹, Taiwan
²智慧半導體納米研究中心, 國立陽明交通大學, 新竹, Taiwan

* Presenter:Wei-Tung Liu, email:25875522liu@gmail.com

Tungsten disulfide (WS2), with a lighter carrier mass among all transition-metal dichalcogenides (TMDs), is attractive with potentially high carrier mobility for next-generation electronic devices [1]. In advance of future application, we should overcome an obstacle, a relatively high contact resistance between metals and TMD materials, which results inthe poor performance of electronic devices and impedes the further application of two-dimensional materials.

Nickel is often used as the contact metal in modern electronic devices. We have tried growing Ni islands on pristine WS2 under an ultra-high vacuum condition, but a scanning tunneling microscopy (STM) study revealed that Ni atoms form large and irregular size and shapes clusters, which is unideal as metal-TMD contact.

Here, we tried to develop a better formation for Ni grown on the WS2 surface by exposing it to cracked H to introduce S defects on the surface. STM images clearly show that the Ni islands grow layer-by-layer mode on the defective surface instead of island growth on the pristine surface. This change in the growth behavior is expected to improve the contact resistance in the electronic device in future studies.

Keywords: contact resistance, transition-metal dichalcogenides (TMDs), defects, scanning tunneling microscopy (STM)