Graphene Films Prepared Using Energetic Physical Vapor Deposition
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Graphene Films Prepared Using Energetic Physical Vapor Deposition Daniel T. Oldfield 1,2, Chi P. Huynh 3, Stephen C. Hawkins 3,4 and Dougal G. McCulloch1 1. 2. 3. 4.
Physics, School Sciences, RMIT University, Melbourne, Victoria 3000, Australia CSIRO Materials Science and Engineering, Bayview Ave, Clayton, Victoria 3168, Australia Department of Materials Engineering, Monash University, Clayton, Victoria 3800, Australia School of Mechanical and Aerospace Engineering, Queen's University Belfast, Belfast BT9 5AH, United Kingdom
ABSTRACT Carbon films were energetically deposited onto copper foil using the physical vapor deposition technique filtered cathodic vacuum arc. Raman spectroscopy and x-ray absorption spectroscopy showed that high quality graphene films of uniform thickness can be deposited onto copper foil at temperatures of 850 °C. The films can be prepared at high deposition rates (~1 nm/min) and were comparable to graphene films grown at 1050 °C using chemical vapor deposition. This lower growth temperature was made possible by the energetic carbon flux which assisted the arrangement of carbon atoms into graphene layers on the Cu growth surface. Floating substrate potential was found to produce the highest quality graphene and the addition of hydrogen gas during film growth resulted in more defective films. INTRODUCTION Graphene is a single layer of sp2 bonded carbon atoms which form a hexagonal lattice. It was first practically isolated from graphite in 2004 via mechanical exfoliation and has since attracted much attention due to its remarkable properties [1]. For example graphene has a room temperature electron mobility of 1.2 x 105 cm2V-1S-1 [2], the highest of any semiconductor or conductor. Graphene is also transparent, absorbing only 2.3% of incident light per layer over a 400 – 7000 nm range [3] and has been shown to have a thermal conductivity of 5.3 kW/m.K [4]. The outstanding properties of graphene make it a potential candidate for a range of applications such as organic solar cells, ultra capacitors, biosensors, nano-electronics and batteries. For a large-scale graphene application to be commercially viable, a fabrication method is needed that is controllable, scalable, cost effective and produces minimal defects. A range of methods are currently being employed to produce graphene, such as the sonication of thermally expanded graphite (as graphene oxide) [5], epitaxial growth on silicon carbide [6], exfoliation [7], chemical vapor deposition (CVD) [8] and plasma enhanced CVD [9]. CVD is considered to produce the highest quality large-area sheets of graphene at the lowest cost [10]. However CVD is very sensitive to growth conditions (e.g. gas concentration, deposition time, temperature and substrate) [11]. A less studied technique to produce graphene is physical vapor deposition (PVD). Despite it being widely used to produce carbon materials such as tetrahedral amorphous carbon and a range of nanostructured graphitic materials [12], there is relatively little published on graphene synthesis [13].
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