H. Ghamlouche

Fabrication of size-selected Pd nanoclusters using a magnetron plasma sputtering source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. Plasma sputtering vaporizes the target’s material forming nanoclusters by inert gas condensation. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters’ size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters’ size distribution on various source parameters, such as the sputtering discharge power, inert gas flow rate, and aggregation length have been investigated. This work demonstrates the ability of tuning the palladium nanoclusters’ size by proper optimization of the source operation conditions. The experimental nanocluster sizes are compared with a theoretical model that reveals the growth of large nanoclusters from “embryos” by a two-body collision. The model is valid for a specific range of deposition parameters (low inert gas flow rates and aggregation lengths equal or below 70 mm).

Electrical properties of Se2Sb2Te6 thin films

The electrical properties of Se2Sb2Te6 thin films are investigated using dc resistance, impedance spectroscopy and capacitance–voltage (C–V) measurements. The amorphous–crystalline transition temperature, Tc, is estimated to be 60 °C using dc resistance measurements. The impedance spectroscopy measurements are performed at different temperatures ranging from 25 to 95 °C. The impedance spectroscopy data give an estimation of the activation energy, Ev = 0.5 eV. The amorphous–crystalline interface is electrically characterized by measuring the capacitance of the film as a function of bias voltage at different temperatures ranging from 25 to 85 °C. The C–V measurements show temperature dependence and nonlinear behaviour of the capacitance with the applied bias voltages that could be attributed to the crystallization growth as the temperature gets close to Tc.

Electrical and optical properties of indium-modified Se 2 Sb 2 Te 6 films

The electrical and optical characteristics of indium-doped Se2Sb2Te6 phase-change alloy are studied in this paper. It is found that adding indium to Se2Sb2Te6 alloy increases its amorphous‐crystalline transition temperature, TC, and reduces the electrical conduction activation energy. The capacitance‐temperature measurements showed a drastic change in the capacitance of the modified film as the temperature approaches TC and eventually the capacitance becomes negative and nonlinear. The negativity and nonlinearity in the capacitance‐voltage dependence can be attributed to the growth of conductive crystalline islands with increasing temperature.

Production and Growth Mechanisms of Pd Nanoclusters

Size-selected palladium nanoclusters have been produced by dc sputtering and inert gas condensation technique using mixtures of argon and helium gases. By controlling the source parameters, it was possible to produce Pd nanoclusters with size in the range of 2-10 nm. Transmission electron microscopy (TEM) images were used to confirm the produced sizes of nanocluster. It was found that increas- ing the percentage of helium to argon have two main effects: i) decreases the nanocluster size as a result of the high drift velocity of he- lium, and ii) decreases the number of measured nanoclusters due to the low sputtering yield of helium. Since He gas is primarily respon- sible for the cluster-condensation process, its partial pressure can be used to control the nanoclusters growth. The source parameters and their effects on the size and number of nanoclusters are of great importance in understanding the Pd nanoclusters growth mechanism.

Investigation of the Formation Mechanisms of Pd Nanoclusters Produced Using a Magnetron Sputtering Source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters’ size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters’ size distribution on various source parameters, such as the inert gas flow rate, and aggregation length have been investigated in details. This work demonstrates the ability of tuning the palladium nanoclusters’ size by proper optimization of the source operation conditions.

Simulation of Microwave Losses of Superconductive Microstrip Line Resonators and Filters Using Commercial Software

The microwave losses of double-sided superconducting YBa2Cu3O7 − x thin films is presented. The films were grown on both sides of LaAlO3 substrates. The microstrip resonators and the filters were patterned and etched using the technique of photolithography. The performance of high frequency microstrip resonator was studied for a resonance frequency of 5 GHz and for a temperature range of 17–100 K. The power dependence of the quality factor measured and the shift in the resonant peak with respect to temperature are also reported. We performed simulations using two phenomenological models. These models were confirmed by our experimental results. Several commercial software were used in our simulations, with appropriate modifications. We were able to reproduce our experimental results using the models mentioned above. The physical parameters used in the model were chosen from among those reported and accepted in literature. In order to validate these models we designed a band-pass filter. Theoretical simulation was performed on a two-pole filter using the models mentioned above. Then two real filters have been prepared using the technique of photolithography. Experimental measurements have been performed on these filters. Comparison between the experimental and simulation results are presented. The goal of this paper is to demonstrate that it is possible to use commercial software to design planar microwave devices by performing only few appropriate modifications.

Electrical and Optical Properties of Indium-Modified SeSbTe Thin Films for Low Power Memory Devices

The electrical and optical characteristics of indium doped Se2Sb2Te6 phase-change alloy are studied. It is found that adding indium to Se2Sb2Te6 alloy (In0.3Se2Sb2Te6) increased the crystallization temperature and reduced the electrical conduction activation energy. The capacitance-temperature measurements showed a drastic change in the capacitance of the modified film when the temperature approaches the crystallization temperature, and eventually the capacitance becomes negative and nonlinear. The negativity and nonlinearity in the capacitancevoltage dependence can be attributed to the growth of conductive crystalline islands by increasing the temperature.