David M. A. Mackenzie: High-speed debris-free laser fabrication of wafer-scale graphene devices

David M. A. Mackenzie, Jonas D. Buron, Patrick R Whelan, Bjarke S. Jessen, Adnan Silajdzic, Amaia Pesquera, Alba Centeno, Amaia Zurutuza, Peter Bøggild, Dirch H. Petersen Department of Micro & Nanotechnology, Technical University of Denmark, Building 345E, 2800 Kgs. Lyngby, Denmark As graphene is up-scaled to wafer-sized production, it is important to have a robust, fast and accurate method for routine characterization of the electrical properties on large scale. Here we consider a fabrication procedure involving wafer-scale laser fabrication of graphene devices to serve this purpose. The inherent advantages of this method include the high speed of device fabrication and the prevention of degradation of the electrical properties associated with traditional lithographic methods:  i.e. avoiding contact to polymers/liquids, known to adversely affect the electrical properties [1].  Commercially purchased CVD graphene (covering a 4-inch Si wafer on SiO2) has metal electrodes (Ti/Au) deposited using electron-beam evaporation through a stencil shadow mask. The graphene is then patterned via ablation (see Figure 1) with a pulsed laser to define large devices (Hall bars or van der Pauw geometries), enabling the large-scale electrical properties to be tested.  Optical microscopy and Raman Spectroscopy were used to assess ablation of the graphene, as well as stylus profilometery indicating no damage of the SiO2 substrate. CVD graphene devices were electrically characterized and showed comparable field-effect mobility, doping level, on-off ratio, and conductance minimum before and after laser ablation fabrication. Further details can be found here [2]. [1] A. M. Goossens et al, Appl. Phys. Lett. 100, 073110 (2012) [2] David M A Mackenzie et al 2015 2D Mater. 2 045003 David Mackenzie is a researcher in the Nanocarbon group based at the Department of Micro & Nanotechnology, Technical University of Denmark. Research interests include fabricating graphene devices, electrical and gas sensing measurements.