NaCl-Assisted CVD Synthesis, Transfer and Persistent Photoconductivity Properties of Two-Dimensional Transition Metal Di
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.156
NaCl-Assisted CVD Synthesis, Transfer and Persistent Photoconductivity Properties of Two-Dimensional Transition Metal Dichalcogenides 1,2,4,6 1,2 1 1 1 1,2 Yong Xie , Xiaohua Ma , Zhan Wang , Tang Nan , Ruixue Wu , Peng Zhang , 1,2 5 3 2 Haolin Wang , Yabin Wang , Yongjie Zhan , Yue Hao 1School of Advanced Materials and Nanotechnology, Xidian University, Xi’an 710071, China 2Key Laboratory of Wide Band-Gap Semiconductor Technology, Xidian University, Xi’an 710071, China 3Institute of Photonics and Photon Technology, Northwest University, Xi’an 710069, China 4 Case Western Reserve University, Cleveland, OH 44106, USA 5Universität Erlangen-Nürnberg, Erlangen 91058, Germany 6 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
ABSTRACT
Transition metal dichalcogenides (TMDC), such as MoS2, WS2 have attracted attention due to their mechanical and electronic properties in their two dimensional (2D) structures. Here, we report a facile growth of monolayer TMDC using oxide source materials with the assistant of NaCl. The addition of NaCl can enhance the lateral growth and widen the growth window of TMDC. Through carefully controlling the growth parameters, large area growth of TMDC can be achieved. Two steps E-beam lithography was utilized to fabricate electrodes of TMDC. The phototransistors made from the CVD grown TMDC show strong persistent photoconductivity (PPC). It was finally shown that TMDC device capping with h-BN could have suppressed PPC effects.
INTRODUCTION Two-dimensional (2D) atomically thin transition metal dichalcogenides(TMDC) (eg. MoS2, MoSe2, WS2, WSe2, MoTe2) have attracted intense interest [1]. TMDC can be fabricated down to monolayer limit by exfoliation[1] and chemical vapor deposition (CVD)[2, 3] etc., which has transition from indirect bandgap at bulk to direct band gap at monolayer. Large area and uniform CVD growth of TMDC guarantee the applications such as low power field effect transistor[4], sensitive photodetectors[5], gas sensors[6] and bio sensor[7] etc.
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Here, a very facile growth recipe with assistant of NaCl is used for the growth of large area and high optical quality monolayer TMDC. Growth can take place on SiO2 substrate without certain treatments like perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) seeding[8] or oxygen plasma[9]. No additional hydrogen or low pressure is needed, which demonstrate the feasibility of the growth method. Our results indicate the growth of monolayer TMDC could benefit from the precise control of the introducing time of sulphur and the ratio of (Mo, W)/(S, Se, Te). The growth of TMDC could be easily expanded to inch size. Devices made from CVD growth MoS2 show
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