© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 4521 www.advmat.de www.MaterialsViews.com wileyonlinelibrary.com COMMUNICATION Di-Yan Wang, I-Sheng Huang, Po-Hsun Ho, Shao-Sian Li, Yun-Chieh Yeh, Duan-Wei Wang, Wei-Liang Chen, Yu-Yang Lee, Yu-Ming Chang, Chia-Chun Chen,* Chi-Te Liang, and Chun-Wei Chen* Clean-Lifting Transfer of Large-area Residual-Free Graphene Films Dr. D.-Y. Wang, [+] P.-H. Ho, Dr. S.-S. Li, Y.-C. Yeh, Prof. C.-W. Chen Department of Materials Science and Engineering National Taiwan University Taipei 106, Taiwan E-mail: chunwei@ntu.edu.tw I.-S. Huang, [+] D.-W. Wang, Prof. C.-C. Chen Department of Chemistry National Taiwan Normal University Taipei 116, Taiwan E-mail: cjchen@ntnu.edu.tw Dr. W.-L. Chen, Y.-Y. Lee, Prof. Y.-M. Chang Center for Condensed Matters Sciences National Taiwan University Taipei 106, Taiwan Prof. C.-C. Chen Institute of Atomic and Molecular Sciences Academia Sinica, Taipei 106, Taiwan Prof. C.-T. Liang Department of Physics National Taiwan University Taipei 106, Taiwan [+] Dr. D.-Y.W. and I-S.H. equally contribute to this work. DOI: 10.1002/adma.201301152 Graphene, consisting of a single atom-thick plane of carbon atoms arranged in a honeycomb lattice, exhibits excellent car- rier transport properties, which is attributed to its unique two- dimensional (2D) energy dispersion. [1] Graphene also shows a high transparency with a transmittance of 97.7% for single-layer graphene, [2] making it a promising candidate for transparent electrode applications. [3] The best-quality graphene in terms of structural integrity is obtained by mechanical cleavage of highly oriented pyrolytic graphite. [4] However, mechanical exfoliation typically yields relatively small samples that cannot address the need for mass fabrication of large-area uniform monolayer graphene. Recently, high-quality graphene films have been grown using the chemical vapor deposition (CVD) method onto SiC substrates [5] or transition metal substrates such Cu, [6] Ni, [7] Pd, [8] Ru, [9] or Ir. [10] In particular, the development on a uniform single-layer deposition of graphene on Cu foil over large area has allowed the access to high-quality graphene for industrial applications. [6] The critical step to use CVD-grown graphene for most practical applications is to transfer graphene from the metal growth substrates onto various desired sub- strates without degrading the quality of graphene. [11] The most popular method is to use poly(methyl methacrylate) (PMMA) as a carrier material for transferring graphene onto target sub- strates. [12] In this approach, a layer of PMMA is coated onto graphene, and the metal substrate underneath is etched away. The floating PMMA/graphene stack is transferred onto a target substrate, followed by using solvent rinsing to remove the PMMA. However, this method suffers from PMMA residues left on the graphene surface, and the solvent rinsing process may also cause graphene-surface tearing, which may introduce structural discontinuities such as cracks in the film [13,14] (see also the Supporting Information). In addition, this wet process is unsuitable for preparing large-scale and uniform graphene films because of the difficulty in handling the spin-coated PMMA layers due to their weak mechanical strength. A recent report showed the “roll-to-roll”(R2R) transfer technique, which uses a thermal release tape as a temporary support, enabling the continuous production of graphene films at meter scale on flexible substrates for industrial applications. [15] However, this transfer approach inevitably contaminates the transferred gra- phene surface with organic adhesive from the thermal release tape (see Supporting Information), which may considerably degrade the electrical properties of the transferred graphene films. [16] This R2R transfer also causes undesired mechanical defects on graphene films when it is applied to rigid substrates such as SiO 2 /Si wafers or glass substrates. [17] In this work, we developed a unique technique called the “clean-lifting transfer (CLT)” method using electrostatic force to transfer graphene onto target substrates, which does not involve using any organic support or adhesives, and has excellent scalability in produc- tion. This new CLT technique, which enables the clean transfer of CVD-grown graphene, provides an efficient route to develop the cost- and time-effective production of high-quality large- scale graphene-based electronics for industrial applications. Electrostatic force is the phenomenon that results from slow- moving or stationary electrical charges. Electrostatic attraction has recently been used to transfer loosely bound small gra- phene flakes on freshly cleaved HOPG surfaces to a selected substrate. [18] However, these methods using a high voltage source or a high electric field between two separated electrodes only allow the transfer of very small graphene flakes (micro- meter size). To obtain large-area and high-quality graphene films using the CLT technique, we employed an electrostatic generator (SIMCO, 18 kV), which provides uniform negative charges on various target substrates, to transfer CVD-graphene grown on Cu foil. The electrostatic generator was placed at a distance of 1 inch. away from the substrate ( Figure 1a), and the discharge process occurred between the electrostatic Adv. Mater. 2013, 25, 4521–4526