Direct formation of wafer-scale single-layer graphene films on the rough surface substrate by PECVD Liangchao Guo a, b , Zhenyu Zhang a, * , Hongyan Sun b , Dan Dai b, c , Junfeng Cui a, b , Mingzheng Li a, d , Yang Xu c , Mingsheng Xu c , Yuefeng Du b , Nan Jiang b , Feng Huang b , Cheng-Te Lin b, ** a Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China b Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences, Ningbo 315201, China c State Key Laboratory of Silicon Materials, College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, P.R. China d School of Engineering, University of Liverpool, Liverpool L69 3GH, UK article info Article history: Received 9 July 2017 Received in revised form 25 November 2017 Accepted 7 December 2017 Available online 7 December 2017 abstract The technical advance of plasma enhanced chemical vapor deposition (PECVD) exhibits the potential to grow large-area high-quality graphene films at relatively low growth temperature, which is beneficial to the fabrication of graphene-based electronic devices/sensors and transparent electrode. However, it remains a challenge to overcome the degradation of graphene quality during growth by PECVD, due to the continuous bombardment of plasma ions on the catalyst surface. Herein, the combined techniques of PECVD and the growth of graphene underneath the catalyst layer were proposed. As a result, transfer- free single-layer graphene films with 2.5 inch in diameter on quartz substrate can be obtained with the growth temperature of 700  C, which is 250  C lower than that for graphene synthesis using thermal CVD. The graphene films prepared by our method show the ability to form on the rough surfaces with millimeter-scale grooves and have minimal surface contamination, compared to that of conventionally transferred CVD graphene. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Graphene, an atomically thin crystal with sp 2 -arranged carbon atoms [1], has attracted numerous interests due to its ultrafast carrier mobility [2], excellent mechanical strength [3], almost transparent in visible light region [4], and high thermal conduc- tivity [5,6]. So far, various methods have been developed toward mass production or large-area synthesis of graphene and its de- rivatives, such as Hummer's method [7], chemical vapor deposition (CVD) [8e10], and vacuum evaporation of single-crystal 6H-SiC [11,12] etc. Owing to the great demand of large-area high-quality graphene for advanced sensing and transparent conducting appli- cations, CVD technique has been widely investigated to prepare graphene films at the growth temperature of 950e1100  C with the assistance of metal catalysts [13e16]. However, because of the large difference of their coefficient of thermal expansion (e.g. Cu: 2.6  10 5 /  C, graphene: 2.0  10 6 /  C) [17,18], the formation of wrinkles and cracks on the obtained graphene is unavoidable, leading to the degradation of graphene properties. Recently, plasma enhanced CVD (PECVD) has emerged as a promising route for the synthesis of graphene at relatively low growth temperature, because the employment of plasma enables to promote the decomposition of methane precursor to form highly reactive spe- cies (like methyl radicals) [19e22]. Kim et al. reported that gra- phene films could be formed at 400  C on an Al foil by surface wave PECVD [23]. However, the sample is highly defective based on a high I D /I G ratio (z2.5) in its Raman spectrum. Qi et al. synthesized graphene on a Ni film at 650  C using radio frequency PECVD [24], but, the layer number of graphene is not uniform and multilayer graphene can be often found. Therefore, it remains a challenge to prepare wafer-scale, single-layer graphene films at lower growth temperature. In a PECVD configuration, there is a technical issue which * Corresponding author. ** Corresponding author. E-mail addresses: zzy@dlut.edu.cn (Z. Zhang), linzhengde@nimte.ac.cn (C.-T. Lin). Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon https://doi.org/10.1016/j.carbon.2017.12.023 0008-6223/© 2017 Elsevier Ltd. All rights reserved. Carbon 129 (2018) 456e461