ABSTRACT
Molecular sensor development requires the fabrication of structures with nanometer precision. Recently, graphene or few-layer graphene (FLG) has been proposed as a material for making advanced electronic devices. The transport properties of graphene, a single-atom-thick layer of graphite (~0.35 nm) [1], are influenced by atomic-scale defects, and, more importantly from a sensor perspective, by adsorbates [2,3] and the local electronic environment. Highly oriented pyrolytic graphite (HOPG) is one of the best precursors for generating high-quality, crystalline graphene [1], which fortuitously is also an ideal substrate material for high-resolution atomic force microscope (AFM) studies [4]. Several approaches have been used to produce graphene for large-area electronics, including epitaxial growth [5–8], transfer-printing [9,10], electrostatic deposition [1,11], and solution-based deposition [12,13]. At the same time, efforts have been made to tailor graphene sheets into nanoscale features [9,14–17]. Keun et al. developed chemical vapor deposition (CVD) to grow a graphene layer on nickel films and transferred them to polydimethylsiloxane (PDMS) using an etching method [18,19]. However, the incompatibility between PDMS and the mechanical properties of graphene usually causes breaks during the fabrication process, especially during the etching step [20]. For large-scale production, CVD is a promising technique; however, the quality of the graphene layers (roughness) requires improvement. Novoselov et al. described a very simple sticky tape method [21]. First, press the adhesive tape onto a sample of graphite and pull. Then, repeatedly stick the carbon-covered tape against itself and peel away. Thereby, the first carbon flake breaks up further into thin, hundred-micron-wide fragments. Then, press this carbon-coated tape onto an Si surface and carefully remove the tape. Some single- or few-layer graphene will adhere to the Si substrate. However, one cannot mass-produce graphene with the sticky tape method. Liu et al. used a chemically modified silicon wafer to covalently attach graphene [22]. For graphene-based 384electronics, fabrication on chemically modified silicon will be difficult to control. To prepare a few hundred microns long graphene wires and to avoid the wet etching or chemical step, in this chapter, the authors demonstrate a different process for patterning HOPG, producing ordered features at the micron and ~100 nanometer scales. Two different methods are used to transfer the patterned graphene onto substrates for characterization, a thermal tape (T-tape) method to transfer onto glass and direct transfer onto a PDMS substrate, both performed without applying any electrostatic force [11].
