Graphene Based-Biosensor: Graphene Based Electrolyte Gated Graphene Field Effect Transistor

Background of Graphene Based-Biosensor

Graphene is a monolayer of sp² bonded carbon atom, this sp² bond makes the graphene structure apparently looks like honeycomb crystal as shown in Figure 1. Graphene is called the mother of graphite (many layers of graphene), because it can act as basic building block of these allotropes(Enoki, Kobayashi, & Fukui, 2007). Graphene is theoretically discovered back in the 1940s, however at that time graphene (a 2D layer crystal) are believed thermodynamically too unstable to be produced in real world(Wang & Hu, 2012). After Andre Geim and Konstanstin Novoselov successful production of graphene by scotch tape in 2004 the research attention has been moved forward on graphene strongly(Wang & Hu, 2012).

Figure 1.

Monolayer graphene structure with one atom thickness

There are few ways to produce graphene other than mechanical exfoliation, the common ways are Epitaxial grown, Reduced Graphene Oxide and Chemical Vaporization Deposition (CVD) (J.-L. Chen & Yan, 2010). The main reason to focus on graphene production is its promising electrical property and applications (Liu, Tian, Wang, & Sun, 2011). Intrinsic graphene actually has no band gap, which is unfawerable but we can produce a tune-able band gap of graphene. Firstly is to make it bilayer, then induced E-field to the bilayer or by doping the graphene chemically (M. J. A. Kiani, M T. Rahmani, M. Harun, FK Che, 2013; Mak, Lui, Shan, & Heinz, 2009).

Different layers of graphene indicate different electrical properties. In this part two diverse stacking structures (AA and AB) for bilayer graphene nanoribbons (BGNs) with armchair edge are studied (Barbier, Vasilopoulos, Peeters, & Pereira, 2009). The AA-stacked configuration is metallic, but the AB-stacked which is in our focus behaves like a semiconductor material (with a band gap of 0.02 eV). In the AB structure of bilayer graphene with hexagonal carbon lattice the atoms where located on the top layer of BGNs called A1 and B1, whereas atoms on bottom layer of BGN are A2 and B2as shown in Figure 2 (Fiori & Iannaccone, 2009).

Figure 2.

Schematic of AB bilayer graphene lattice configuration

By applying an exact electric field on BGNs can open a gap on its band energy(Mousavi, Ahmadi, & Sadeghi, 2011; Sadeghi, Ahmadi, Ishak, Mousavi, & Ismail, 2011). In addition, value of band gap energy by applying voltage can be controlled. Theoretical study on BGNs still is a novel and velocity characteristic based on band structure are unexplored yet.