Gas Opto-Sensing by Graphene Nano-ribbon Photodetector Based on Asymmetric Electrodes

We show an armchair graphene nanoribbon (AGNR) channelof 30 unit cells long and 13 C-atoms wideconnected between asymmetric source-drain structures—i.e., p-type Au/graphene source and n-type Ti/graphenedrain—can operate as gas opto-sensor, under zero external biases at room temperature.The photocurrent spectrum anddensity of state (DOS) for CO and CO2 adsorption on the opto-sensor are calculated by non-equilibrium green function(NEGF) formalismunder monochromatic illuminations of various incident energies in the range of mid infrared (0.1eV) to solar blind ultra violet (5 eV). Under the assumption that the gas molecules adsorb on the AGNR sites withuniform probability distribution and with the scaling rule of tight binding hopping integrals, DOS's indicate that COand CO2 molecules adsorption increase the band gap of pristine AGNR and act as donor and acceptor respectively.Calculations illustrate the shift of the most probable transition between valance and conduction band to the largerphoton energy. These variations appear to be greater with increasing concentration. The results of this theory are ingood agreement with those obtained by density-functional theory calculations.Keywords: Gas photo-sensor; Photodetector; Asymmetric electrodes; Graphene nano-ribbon; Non- equilibrium greenfunction.

کلیدواژه ها:

Gas photo-sensor ، Photodetector ، Asymmetric electrodes ، Graphene nano-ribbon ، Non- equilibrium greenfunction