Showing 2 results for Razi
A. Asgari, S. Razi, F. Ghasemi,
Volume 4, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 4, No. 2, Summer-Fall 2010)
Abstract
In this paper, we present calculations for different parameters of quantum dot infrared photodetectors. We considered a structure which includes quantum dots with large conduction-band-offset materials (GaN/AlGaN). Single band effective mass approximation has been applied in order to calculate the electronic structure. Throughout the modeling, we tried to consider the limiting factors which decline high temperature performance of these devices. Temperature dependent behavior of the responsivity and dark current were presented and discussed for different applied electric fields. Specific detectivity used as figure of merit, and its peak was calculated in different temperatures. This paper indicates the state of the art in the use of the novel III-N materials in infrared detectors, with their special properties such as spontaneous and piezoelectric polarizations. It was found that, III- nitride Quantum dots have a good potential to depress the thermal effects in the dark current which yields the specific detectivity up to~ 2107 CmHz 1/ 2/W at room temperature.
Sepehr Razi, Mahmoud Mollabashi, Khosro Madanipour,
Volume 9, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 9, No 1, Winter-Spring 2015)
Abstract
In this work, potential of the nanosecond laser processing technique on manipulating the surface wettability of 316L bio grade stainless steel is investigated. Results show that the steel wettability toward water, improves significantly after the laser treatment. Different analyses are assessed in correlation with wettability using Scanning Electron Microscope (SEM), Scanning Tunneling Microscope (STM) and Energy Dispersive X-ray spectroscopy (EDX). It is found that the improvement in the wettability relates to the combined effects of the increase in the surface roughness, oxygen content and the form of the created surface morphologies. Laser fluence is found as the most dominant processing parameter and the higher the incident fluence results in the higher surface roughness and improvement of the wettability. However, measurements indicate that all the treated surfaces become hydrophobic after air exposure for a few days. It is shown that the time dependency of the surface wettability relates to the chemical activity and the reduction of the Oxygen/Carbon (O/C) ratio on the treated surfaces. The behaviors are further studied with investigating the effects of the keeping environment. The long-term wettability alteration differs for the samples that are kept in different mediums. Results indicate that the nanosecond pulsed laser treatment is a versatile approach to create either hydrophobic or hydrophilic steel surfaces for industrial and medical applications.