Wafer-Scale and Transfer-Free Growth of WSe2 Monolayers by a Low Temperature Plasma-Assisted Selenization Process with a Sub Ppb NOx Gas Sensoring
Henry Medina1, Shao-Hsin Lee1*, Jian-Guang Li1, Teng-Yu Su1, Yann-Wen Lan2, Chia-Wei Chen1, Yu-Ze Chen1, Arumugam Manikandan1, Yu-Chuan Shih1, Wei-Sheng Lin1, Jian-Hua Yang1, Stuart R. Thomas1, Bo-Wei Wu1,2, Chang-Hong Shen2, Jia-Min Shieh2, Heh-Nan Lin1, Yu-Lun Chueh1
1Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
2National Nano Device Laboratories, Hsinchu 30078, Taiwan
* presenting author:Shao-Hsin Lee, email:lisa11202001@hotmail.com
The synthesis of semiconductors with atomic thicknesses at low temperatures for the development of plastic electronics is difficult because of the reduced mobility. Instead, transition metal dichalcogenides (TMDs) with atomic thicknesses have proven to be versatile materials for several applications. Here, an inductively coupled plasma (ICP) was used to synthesize TMDs through a plasma-assisted selenization process of metal oxide (MOx) at a low temperature. Large area synthesis of WSe2 on a polyimide (30 x 40 cm2) flexible substrate and an 8-inch silicon wafer with good uniformity was demonstrated at the formation temperature of 250 ºC. A few WSe2 monolayers formed at a plasma-assisted selenization temperature of 500 ºC and showed a Hall hole mobility of approximately 40 cm2V-1s-1, while a hole mobility of approximately 6 cm2V-1s-1 was achieved when the plasma-assisted selenization temperature decreased to 250 ºC. More important, NOx gas sensor made of atomically thin films at temperatures as low as 250 ºC on plastic substrates with a sensitivity of 20 % at 25 ppb at room temperature, signal to noise ratio (S/N) of 40 show the potential for the development of low cost plastic electronics and sensors. The low temperature plasma-assisted selenization provides a pathway for the direct formation of TMD monolayers on plastic substrates over a large area without further transfer and can be extended to the synthesis of other chalcogenide materials, which allows the integration of TMD materials with existing technologies that require a lower process temperature with a manageable thermal budget

Keywords: WSe2, transition metal dichalcogenides, plasma selenization, gas sensing, 2D material