Embedment of Multiple Transition Metal Impurities into WS₂ Monolayer for Bandstructure Modulation

Ming-Deng Siao^1*, Yung-Chang Lin², Tao He³, Meng-Yu Tsai^1,4, Kuei-Yi Lee⁵, Shou-Yi Chang⁶, Kuang-I Lin⁷, Yen-Fu Lin⁴, Mei-Yin Chou^3,8, Kazu Suenaga², Po-Wen Chiu^1,3

¹Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
²National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
³Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
⁴Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
⁵Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan
⁶Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
⁷Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan
⁸Department of Physics, National Taiwan University, Taipei 10617, Taiwan

* Presenter:Ming-Deng Siao, email:m10422602@mail.ntust.edu.tw

Band structure by design in 2D layered semiconductors is highly desirable, with the goal to acquire the electronic properties of interest through the engineering of chemical composition, structure, defect, stacking, or doping. For atomically thin transition metal dichalcogenides, substitutional doping with more than one single type of transition metals is the task for which no feasible approach has been proposed. Here, we show the growth of WS₂ monolayer co-doped with multiple kinds of transition metal impurities via chemical vapor deposition controlled in a diffusion-limited mode. Tetra-atomic embedment of Cr, Fe, Nb, and Mo into the host lattice is exemplified. Abundant impurity states thus generate in the band gap of the resultant WS₂ and provide a robust switch of charging/discharging states upon sweep of an electric filed. A profound memory window exists in the transfer curves of doped WS₂ field-effect transistors, forming the basis of binary states for robust nonvolatile memory. The doping technique presented in this work brings us one step closer to the rational design of 2D semiconductors with desired electronic properties.

Keywords: chemical vapor deposition, doping, transition metal dichalcogenides, memory, WS₂