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Proceedings of the 4th International Conference on

Nanostructures (ICNS4)12-14 March 2012, Kish Island, I.R. Iran

Abstract Book|INST| Sharif University of Technology| 173

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Intersubband transitions in quantum dots (QDs) for infrared light de-

tection have been the subject of much research. Usually QDs are pro -

duced by the Stranski-Krastanov growth method, but the sizes of QDs

fabricated by this method have a random distribution. The QDs absorp-

tion spectrum will therefore not be narrow enough. The main goal of

this paper is to study the effect of size on the major parameters of QD

photodetectors. We use a numerical method and one-band envelope

function formalism for electrons in the conduction band of QDs, with

a position-dependent effective mass. Assuming QDs to have a lens-like

shape, embedded in a cylindrical matrix, we calculate selection rules,

transition energies, and oscillator strengths for the rst Z-polarized and

in-plane polarized incident light transitions as a function of QD vol-

ume, base width, and height.

Keywords: Quantum dot; Intersubband transitions; Infrared photode-

trctors; GaN/AlN

M. H. Zarei*, M. J. Sharif

Faculty of Electrical and Computer Engineering, Shahid Beheshti Univer-

sity, Tehran, Iran

*zarei_mohammad_h@yahoo.com

The Eect of Size and Light Polarizaon on OscillatorStrengths and Intersubband Transions in GaN/AlN

Quantum Dot

Nucleation stage and bulk growth structure are simulated with oblique

angle deposition by Monte Carlo method. In nucleation and columns

growth, Lennard-Jones potential has been used for atoms interaction

with each other. The model based on deposition of incident particles

directly under certain incident angle and particles surface diffusion.

The particle surface diffusion was designed by random walk to rst

neighbour with probability due to potential. Our results show with in-

creasing temperature, cluster number reduces and at certain tempera-

ture, island largest size becomes maximum.

Keywords: Simulation; Temperature; Thin layer growth

M. Abdollahi, R. S. Dariani*

Department of Physics, Alzahra University, Tehran 1993891176, Iran

*dariani@physics.queensu.ca

Eect of Temperature Variaon on Thin Layer Growthby Monte Carlo Simulaon Method

The properties of nitrogen doped model of (5, 5) armchair beryllium

monoxide nanotubes (BeONTs) have been investigated by density

functional theory (DFT) and chemical shift parameters were calculat-

ed. A BeONT consisting of 60 Be, 60 atoms of O, and having a length

of 1.67 nm was studied. Each end of the nanotube was capped by tenhydrogen atoms. The calculated results indicate that by N-doping of

O atom, the chemical shift (CS) parameters of9Be and 17O atoms are

un-affected but N-doping of Be atom affects the CS parameters of O

atoms. These results imply that role of nitrogen as an electron acceptor

is more signicant in the structure for which it dopes for a Be atom.

Keywords:N-doped BeO Nanotubes, Density functional theory

G. Mohseni Roozbahani*, A. Seif

Department of Chemistry, Islamic Azad University, Boroujerd Branch,

Boroujerd, Iran

*Goodarz_mohseni@yahoo.com

The N-doped BeO Nanotubes: A Computaonal Study

the second order energy differences of clusters were calculated and

analysed that they are consistent with the experimental data. The clus-

ters with two and eight atoms are the most stable silver clusters.

Keywords: Density functional theory; Silver cluster; Numerical atomcentred orbitals; FHI-aims

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Theoretical electronic structure studies of the lowest three energy

structures of Tey clusters (y = 2 20) have been carried out using den-

sity functional theory. The results obtained using local density approx-

imation and generalized gradient approximation are compared on the

basis of binding energies, second order differences in total energies,

fragmentation energies and some chemical properties such as electron

afnity, vertical detachment energy etc. A transition from two-dimen-

H. A. Shafei Gol, A. Kshirsagar*

Department of Physics, University of Pune, Pune 411 007, India

*anjali@physics.unipune.ac.in

Ab inio Calculaons of Structural and Electronic

Properes of Te Clusters

sional to three-dimensional structures is observed at y = 5. Te clusters

are exible with dangling bonds, and the exibility increases with the

size of the cluster. Analysis of partial charge density and eigenvalue

spectrum for Tey clusters reveals that there is no s-p hybridization and

the highest occupied states are mostly non-bonding orbitals. Clusters

with even number of atoms show a charge distribution approximately

uniformly localized around each atom similar to the s anti-bonding

orbital in the Te2 dimer. A comparison of the structural and electronic

properties of the Tey clusters (y = 28) with isoelectronic sulfur and

selenium clusters, shows an increasing trend in bond lengths and a de-

creasing trend in bond angles and binding energies from SSeTe.

Keywords: Cluster; lowest energy structures; structural transition;

GGA; LDA