The role of copper pretreatment on the morphology of graphene grown by chemical vapor deposition Tony J. Gnanaprakasa a , Yuanxi Gu a,1 , Steven K. Eddy a,2 , Zhenxing Han a,3 , Warren J. Beck b , Krishna Muralidharan a,⇑ , Srini Raghavan a,c,⇑ a Department of Materials Science and Engineering, The University of Arizona, Tucson, AZ 85719, United States b Department of Physics, The University of Arizona, Tucson, AZ 85719, United States c Department of Chemical and Environmental Engineering, The University of Arizona, Tucson, AZ 85719, United States article info Article history: Received 14 June 2014 Received in revised form 19 September 2014 Accepted 27 October 2014 Available online 5 November 2014 Keywords: Graphene CVD Copper pretreatment Electropolishing Corrosion inhibitor abstract The effect of pretreatment of copper on the ensuing morphology and surface coverage of graphene grown using chemical vapor deposition (CVD) has been investigated. Specifically, graphene grown on electropo- lished copper (EP-Cu) was analyzed with respect to its surface morphology, surface roughness and thick- ness, and compared with graphene grown on as cold-rolled acetic acid cleaned copper (AA-Cu). Results show an improvement in the quality of graphene obtained using EP-Cu over AA-Cu. Additionally, electro- chemical polarization studies were performed on annealed and graphene coated EP-Cu in acidic solu- tions. The results indicate that corrosion inhibition of EP-Cu is possible through the use of graphene films. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Graphene is an exceptionally strong and flexible two- dimensional material, having high optical transmittance, high thermal conductivity and large charge carrier mobility [1–3]. Vari- ous techniques are available for graphene synthesis including mechanical and chemical exfoliation [4], graphene oxide reduction [5], epitaxial growth via high temperature annealing of hexagonal SiC [6,7] and chemical vapor deposition (CVD) on metallic sub- strates [8]. CVD synthesis represents a straightforward process and has therefore been adopted widely for graphene growth. Graph- ene has been synthesized on various transition metals such as Co [9], Pt [10,11], Ir [12,13], Ru [14,15], Ni [16–18] and Cu [19–22]. In particular, Cu has become the substrate of choice for the growth of graphene, due to its ability to mediate the formation of primarily single-layer graphene domains, which is attributed to the low solu- bility of carbon in Cu and the Cu surface driven dissociative adsorp- tion of precursor molecules such as methane [23]. The choice of the precursors dictates the temperature of the CVD growth; the temper- ature corresponding to the most commonly used precursor (meth- ane) is approximately 1000 °C, while lower-temperature CVD growth of graphene can be performed when for instance toluene [24], benzene [25] or ethanol [26] are used. In addition to the choice of precursors and conditions (pressure, temperature) at which CVD is conducted, the quality of CVD grown graphene critically depends on the properties of the Cu substrate such as thickness, surface roughness, polycrystallinity, grain size and orientation and the presence of surface impurities [23,27– 32]. Of particular relevance is the pre-treatment procedure of the Cu substrate prior to graphene growth. Precleaning of Cu by acetic acid is a commonly utilized procedure [33] and aids in removing the native oxide on as-received Cu foils in addition to any possible surface contaminants that would decrease the catalytic activity of Cu. Other suggested precleaning treatments include nitric acid based etchants, which were found to be more effective in produc- ing graphene with lower impurities and less bilayer islands [31]. Nevertheless, chemical-based treatments do not significantly reduce the surface roughness of Cu, which is critical to obtaining flat graphene sheets as well as avoiding possible discontinuities http://dx.doi.org/10.1016/j.mee.2014.10.021 0167-9317/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors at: Department of Materials Science and Engineering, The University of Arizona, Tucson, AZ 85719, United States (S. Raghavan). E-mail addresses: krishna@email.arizona.edu (K. Muralidharan), srini@email. arizona.edu (S. Raghavan). 1 Current address: Department of Materials Science and Engineering, University of Illinois at Urbana Champaign, Champaign, IL 61820, United States. 2 Current address: Advanced Green Innovations, LLC, Chandler, AZ 85226, United States. 3 Current address: Micron Technology, Inc., Boise, ID 83707, United States. Microelectronic Engineering 131 (2015) 1–7 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee