Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe 2 with large domain size and fast growth rate
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Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe2 with large domain size and fast growth rate Mingrui Chen§, Anyi Zhang§, Yihang Liu, Dingzhou Cui, Zhen Li, Yu-Han Chung, Sai Praneetha Mutyala, Matthew Mecklenburg, Xiao Nie, Chi Xu, Fanqi Wu, Qingzhou Liu, and Chongwu Zhou () Mork Family Department of Chemical Engineering and Materials Science, Ming Hsieh Department of Electrical Engineering, Core Center of Excellence in Nano Imaging and Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA § Mingrui Chen and Anyi Zhang contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 21 November 2019 / Revised: 17 May 2020 / Accepted: 21 May 2020
ABSTRACT Orientation-controlled growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs) may enable many new electronic and optical applications. However, previous studies reporting aligned growth of WSe2 usually yielded very small domain sizes. Herein, we introduced gold vapor into the chemical vapor deposition (CVD) process as a catalyst to assist the growth of WSe2 and successfully achieved highly aligned monolayer WSe2 triangular flakes grown on c-plane sapphire with large domain sizes (130 μm) and fast growth rate (4.3 μm·s−1). When the aligned WSe2 domains merged together, a continuous monolayer WSe2 was formed with good uniformity. After transferring to Si/SiO2 substrates, field effect transistors were fabricated on the continuous monolayer WSe2, and an average mobility of 12 cm2·V−1·s−1 was achieved, demonstrating the good quality of the material. This report paves the way to study the effect of catalytic metal vapor in the CVD process of TMDCs and contributes a novel approach to realize the growth of aligned TMDC flakes.
KEYWORDS two-dimensional materials, transition metal dichalcogenides, tungsten diselenide (WSe2), chemical vapor deposition, aligned growth
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Introduction
Two-dimensional (2D) layered materials beyond graphene, especially transition metal dichalcogenides (TMDCs), have attracted a lot of attention in recent years due to their intriguing properties [1, 2]. For example, tungsten diselenide (WSe2), which is one of the well-studied species among the large family of TMDCs, has been demonstrated to be a promising candidate for various applications including field-effect transistors [3–6], sensors [7, 8], and printed and flexible electronics [9–12]. Compared with the mechanical exfoliation method, chemical vapor deposition (CVD) is a better solution to achieve largescale, good-uniformity, and high-yield TMDCs [13–16]. The orientation of TMDCs synthesized by the traditional CVD method is usually random with small size [13, 17–28]. When the growth conditions are precisely controlled, TMDC flakes can merge together to form a continuous film [17, 29]. If the orientation of the TMDC flakes is random, the grain boundaries between two flakes can significantly degrade the electronic properties of the obtaine
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