Nanosensing properties of hydrogenated edge armchair graphene nanoribbons (HAGNR) are investigated. Using non-equilibrium Green’s function method in the tight-binding approach, the effects of hydrogen and oxygen adsorption on current–voltage (I-V) characteristics and also the electrical conductivity of these systems are calculated. We found that theI-V curves of these systems change by the adsorption of hydrogen or oxygen molecules. Also, we found that conductivity of these systems at low adsorption concentrations increases, while at high adsorption, concentrations decrease. This could be explained in terms of semiconducting or metallic properties of the adsorbed system which was obtained from electronic properties of our clean HAGNR system. On the other hand, the local density of states of some sites has a metallic behavior, and that of other sites has a semiconducting behavior. Note that our results are investigated at a fixed temperature T=300 K, i.e., room temperature. By calibrating conductivity in terms of adsorbed gas molecules, one can make a gas nanosensor.

Graphene based optical devices are highly recommended and interested for integrated optical circuits. As a main component of an optical link, a photodetector based on graphene nano-ribbons is proposed and studied. A quantum transport model is presented for simulation of a graphene nano-ribbon (GNR) -based photo-transistor based on non-equilibrium Green’s function method. In the proposed model a self-energy matrix is introduced which takes the effect of optical absorption in GNR channel into account. The self-energy matrix is treated as a scattering matrix which leads to creation of carriers. The transition matrix element is calculated for optical absorption in graphene channel and is used to obtain the optical interaction self-energy. The resulting self-energy matrix is added to retarded Green’s function and is used in transport equations for calculation of current flow in the photo-transistor. By considering the effect of optical radiation, the dark and photocurrent of detector are calculated and results are used for calculation of responsivity.

The importance of constructing the appropriate Green function to solve a wide range of problems inelectromagnetics and partial differential equations is well-recognized by those dealing with classical electrodynamics and related fields. Although the subject of obtaining the Green function for certain geometries has been extensively studied and addressed in numerous sources, in this paper a systematic method using the Method of Separation of Variables has been employed to scrutinize the Green function with Dirichlet boundary condition for the interior region of a closed cylinder. With further rigorous elaboration, we have demonstrated clearly the path through which the Green function can be accomplished. Additional verifications both in analytical and computer-simulating problems have also been performed to demonstrate the validity of our analysis.

By virtue of a complete set of two displacement potentials, an analytical derivation of the elastostatic Green’s functions of an exponentially graded transversely isotropic bi-material full-space was presented. Three-dimensional point-load Green’s functions for stresses and displacements were given in line-integral representations. The formulation included a complete set of transformed stress-potential and displacement-potential relations, with the utilization of Fourier series and Hankel transform. As illustrations, the present Green’s functions were analytically degenerated into special cases, such as exponentially graded half-space and homogeneous full-space bi-material Green’s functions. Owing to the complicated integrand functions, the integrals were evaluated numerically, and in computing the integrals numerically, a robust and effective methodology was laid out which provided the necessary account of the presence of singularities of integration. Some typical numerical examples were also illustrated to demonstrate the general features of the exponentially graded bi-material Green’s functions which will be recognized by the effect of degree of variation of material properties.

In this work, we have performed first principle study on a single-molecule pentacene field effect transistor and studied various oxygen- and hydrogen-induced defects in the same device configuration. Further, we have investigated the effect of these defects on the various electronic transport properties of the device and compared them with those of the original device along with reporting the negative differential region window and the peak-to-valley ratio in different cases. For this purpose, we have applied the density functional theory in conjugation with non-equilibrium green’s function (NEGF) formalism on a 14.11 A pentacene device to obtain the I–V characteristics, conductance curves and transmission spectra in various device scenarios.