JOURNAL OF OPTOELECTRONICAL NANOSTRUCTURES
Year:2016 | Volume:1 | Issue:4|Papers Count:7

In this paper, the effect of the structural properties and morphology of iron oxide product, have been studied in co-precipitation and hydrothermal methods. Also, the effect of adding CCl4 impurities and final annealing of the materials is taken into account. The more homogeneous particle size in hydrothermal method has been explained by the effect of adding CCl4 as impurities to prevent the continuation of nucleation. It has also been observed that in co-precipitation sample additive has a key role for providing the bar shape particles by mediating of the anisotropic connection of nuclei. The difference in the crystal structure of the anneal samples has been related to the oxygen content.

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.

In this article, TiO2 nanotubes fabricated on three titanium foils with different surface morphologies are investigated. Nanotubes anodized on titanium foils with no polishing process (A sample), with electropolishing process (B sample) and with electropolishing process in ethanolic electrolyte (C sample). By electropolishing, the surface roughness decreases considerably. Also, by adding ethanol to the electropolish electrolyte, the surface roughness decreases more in comparison to previous one. By decreasing surface roughness, interesting results are observed: 1) nanotubes diameter size distribution becomes more uniform significantly, 2) ordering of nanotubes increases highly and 3) outer diameter of tubes decreases from 125nm to 92nm.

Numerical modeling of polycrystalline thin-film solar cell serves as an imperative procedure to test the suitability of proposed physical clarification and to anticipate the effect of physical changes on cell performance. All in all, this must be conducted with only partial knowledge of input parameters. In this paper, we evaluated the numerical simulation of CdS/CIGS tandem multi junction solar cells by applying the AMPS-1D software aiming at finding the optimum design of the new multi-junction tandem solar cell preparing the ground for its most efficient operation. We studied the effect of CIGS p-layer thickness on the output parameters of the CdS/CIGS tandem multi junction solar cells, such as the density of short-circuit current, open circuit voltage, fill factor and efficiency. By applying the results of the numerical simulation, it was concluded that the maximum efficiency of this solar cell was equal to 48.3%, which could be obtained with the CIGS p-layer thickness of 600 nm at a standard illumination of AM 1.5.

In this paper, we study the effect of single Boron/Nitrogen impurity atom on electronic properties of a silicene nano flake. Our calculations are based on density functional theory by using Gaussian package. Here, one Si atom in silicene nano flake substitutes with a Boron/Nitrogen atom. The results show that substitution of one Si atom with single Boron/Nitrogen atom increases distance of impurity atom with its nearest neighbors and changes hexagonal structure of silicene nano flake. Doping silicene nano flake with a Boron impurity atom makes its structure curved and causes to create a miniband in energy gap, which increases conductance consequently while doping with a Nitrogen atom causes to produce two spin dependent midbands in energy gap which leads to creating a controllable spin dependent conductance with electron energy for silicene nano flake. Therefore, Nitrogen doped silicene nano flake is good material for design of nano electronic and spintronic devices.

In this paper, we study two different Graded Index (GRIN) photonic crystal (PC) structures which are named as structure type I and type II. The PC structures are made of the square rod in an air background. To design a GRIN PC structure the lattice constant has been altered in the direction transverse to propagation. We investigated focusing effect and waveguiding behavior of electromagnetic waves propagating throughout the GRIN structures. Wide incident beam with a Gaussian profile is illuminated to the both GRIN structures. In the case of structure type I, the incident wave bend toward the central part of the structure and after getting out of it focuses on the narrow area. The designed structure shows the strong focusing effect and increase normalized intensity and decreases the width of the outgoing wave. In the case of structure type II, the incoming beam after traveling short distance becomes distracted to the central part and remains confine in the middle of the structure. The exiting wave can be coupled to a photonic crystal waveguide. Plane wave expansion method has been used for analyzing dispersion relation. Propagation of electromagnetic wave within the graded structure has been simulated using finite-difference time-domain method.

Among graphene-like family, phosphorene is a typical semiconducting layered material, which can also be a superconductor in low temperature. Applying pressure or tension on phosphorene lattice results in changing the hopping terms, which change the energy bands of the material. In this research we use the tight-binding Hamiltonian, including relevant hopping terms, to calculate energy bands of normal and under tension phosphorene. Our results show that the energy gap decreases by decreasing 𝒕𝟐/𝒕𝟏from 3 to 2, and finally the gap disappears.