A new transfer matrix method is further developed to analyze the electron transport in each dual channel under a back gate voltage, while the electronic density of states of graphene ribbons with transversal dislocations are calculated using the retarded Green’s function and a novel real-space renormalization method. In this article, GFETs are investigated within the tight-binding formalism, including quantum capacitance correction, the graphene ribbons with reconstructed armchair edges of which are mapped into a set of independent dual channels through a unitary transformation. ![]() Graphene field-effect transistors (GFETs) exhibit unique switch and sensing features. Copyright 2017, the American Association for the Advancement of Science. After 10 electrochemical cycles cleaning process, the GFET demonstrated a rather symmetric ambipolar behaviour with carrier mobility of 1100 cm 2 V −1 s −1. Lower panel shows the conductance of GFET vs gate potential V ref before electrochemical cleaning (gray line), with the first electrochemical cycle (green line), after 5 electrochemical cycles (blue line), and after 10 electrochemical cycles (red line). (h) The upper panel shows the conductance of GFET during electrochemical cleaning cycles in an operation range from −0.4 V to 0.6 V. The changes of gate voltages applied to the graphene channel are induced by electrooxidation of nitrite at gate electrodes. Copyright 2014, American Chemical Society. The tip potential is 0.4 V and the substrate potential is 0.11 V. (f) SECM images of the same defective graphene patterns. ![]() (e) Raman mapping of defective graphene patterns with various defect densities induced by irradiation. Copyright 2012, American Chemical Society. (d) SECM images of graphene with a mechanically induced defect on SiO 2 substrate. Copyright 2015, American Physical Society. A distinct D peak has emerged after the electrochemical reaction. (c) The Raman spectra of the graphene before gate potential were applied and after the electrochemical reaction occurred. Copyright 2011, American Chemical Society. Inset: the sensitivity of GFET to pH values. (a), (b) The conductance of source and drain vs gate potential V ref of fluorobenzene functionalized and Al 2 O 3 coated GFET device in different pH buffer solutions, respectively. Copyright 2019, American Chemical Society. ![]() Densitydependent graphene mobility at 9 k and room temperature. (d) Schematics of encapsulate graphene in h-BN through a wet transfer process. (c) The Kelvin probe microscopy image of the local electrostatic potential fluctuations on h-BN substrate and bare SiO 2 substrate. The annealing process has a restoring effect of the high electrical conductance and Dirac point of the graphene. (b) Histogram of mobility and the Dirac point of different graphene on bare SiO 2 substrate and on OTMS-modified SiO 2 substrate. Copyright 2010, American Chemical Society. The annealing process in vacuum at 140 ☌ for 1 h resulting in a shift in a shift of the Dirac Point to near-zero gate voltage. (a) Mobility and Dirac point of different graphene transfer to SiO 2 substrate with or without HDMS. (g) The geometrical capacitance, quantum capacitance, double layer capacitance of graphene as a function of the number of graphene layers. The equivalent circuit is shown on the left side of the scheme. The electric double layer is about 1 nm in thickness. (f) A cross-sectional scheme of graphene channel-electrolyte-gate electrode interface capacitance. (c)-(e) The current response of graphene FET is varied with the charged target biomolecules on the surface. The semimetallic nature makes graphene as a hole conductor when applied negative voltage while positive gate makes it an electron conductor. The work function of graphene is around 4.6 eV. The Ag/AgCl reference electrode with an electrochemical potential around 4.7 eV is used as the gate electrode. (b) A momentum-energy illustration of the graphene-solution interface. (a) The cross-sectional scheme of the graphene solution-gated FET biosensor.
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