Physics

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Shiv Nadar University

Lead sulfide (PbS) nanoparticle films were chemically grown on glass, quartz and silicon substrates. Structure and size of PbS nanoparticles were characterized by X-ray diffraction and transmission electron microscopy (TEM), respectively. Large optical band gap has been observed in these films. The decreases in dc-conductivity, Hall mobility and carrier concentration with reducing grain size were also examined. Heterojunctions of p-PbS/n-Si were fabricated and photovoltaic effect was observed in these self-assembled heterojunctions. © 2003 Elsevier B.V. All rights reserved.

World University root node

(SoNS) School of Natural Sciences

Applied Surface Science

Solution grown PbS nanoparticle films

The solid-phase epitaxial regrowth of Rb-irradiated α-quartz during annealing was investigated. The depth distribution of Rb atoms and the thickness of the amorphous layers calculated using Rutherford backscattering and Channeling (RBCS) spectrometry. It was observed that the chemically guided epitaxy in α-quartz demonstrated the correlations which governed the epitaxial regrowth, the Rb out-diffusion, and the oxygen exchange between the silica matrix and annealing gas. The results show that the swelling of the SiO2 matrix during implantation and recompaction during epitaxy was proven by the surface topography measurements.

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Journal of Applied Physics

Chemically guided epitaxy of Rb-irradiated α-quartz

The effect of swift-heavy-ion irradiation on a very stable and well-studied Al62Cu25.5Fe12.5 icosahedral quasicrystalline system is discussed here. The experiments are performed in the pure electronic excitation regime, where various ranges of energy (1.2 to ∼2.5 keV/Å) are systematically deposited in to the system, causing electronic excitations in them. The choice of ions was generally dependent on calculations based on Monte-Carlo simulations and some existing literature studies on metals/metallic alloys. Samples were irradiated at fluences of 1011 to a few 1013 ions/cm2, and a homogeneous irradiation was ensured. The effect of these electronic excitations on the electronic structure of the quasicrystals is analyzed by doing in situ resistivity vs. fluence and ex situ resistivity vs. temperature measurements, made on the irradiated pieces. © 2004 Published by Elsevier B.V.

Journal of Non-Crystalline Solids

Swift-heavy-ion irradiation on Al62Cu25.5Fe 12.5 quasicrystals

This article reports on the formation of iron nitrides during nitrogen ion irradiation of Fe/Si bilayers at room temperature. The 30 nm 57 Fe/Si bilayers were prepared by pulsed laser ablation and irradiated with 22 keV N 2+ ions at fluences of (0.6-2)×10 17 ions/cm 2 . The structural changes and phases formed by irradiation were analyzed by Rutherford backscattering spectroscopy (RBS), X-ray diffraction analysis (XRD) and conversion electron Mössbauer spectroscopy (CEMS). The results clearly show the formation of several iron nitrides. At the lower fluences, the samples contain a mixture of ε-Fe 2+x N and α-Fe with nitrogen interstitials. For the highest fluence, the paramagnetic ε-Fe 2 N (61%) phase predominated. It can be concluded that the elemental iron almost fully transforms to an iron-nitride layer, but that no iron silicides are formed. © 2003 Elsevier B.V. All rights reserved.

Thin Solid Films

Formation of iron-nitrides by irradiation of 57 Fe/Si bilayers with N 2+ ions

The magnetic behavior of (Al,Ge)65CuMn quasicrystalline samples with ∼22 and 24 at.% Mn was investigated. High disordered magnetism was observed for these quaternary alloys. Short-range ferromagnetism in samples with high Ge and high Mn content along with the oscillatory magnetization were also observed. A double transition at T&lt;75 K was observed in the sample with 0 at. % Ge. The results indicate that with the increase in the concentration of icosahedral phase in the alloys, magnetic disorder increases.

Magnetic behavior of (Al,Ge)65CuMn quaternary alloy quasicrystals

The doping single-crystalline α-quartz with 120 keV Ge +-ion implantation under the condition of dynamic solid phase epitaxial regrowth was discussed. The light emitting properties possibly suitable for optoelectronic devices were analyzed by measuring cathodoluminescence spectra. It was found that the Ge implantation produced amorphous layers varying in depth with temperature. Analysis shows that at a fluence of 7×10 14 Ge-ions/cm 2 and an implantation temperature of 1073 K, Ge implantation was accompanied by a strong increase in the luminescence.

Stable violet cathodoluminescence of α-quartz after Ge + implantation at elevated temperature

A systematic procedure to study one-dimensional Schrödinger equation with a position-dependent effective mass (PDEM) in the kinetic energy operator is explored. The conventional free-particle problem reveals a new and interesting situation in that, in the presence of a mass background, formation of bound states is signalled. We also discuss coordinate-transformed, constant-mass Schrödinger equation, its matching with the PDEM form and the consequent decoupling of the ambiguity parameters. This provides a unified approach to many exact results known in the literature, as well as to a lot of new ones.

Modern Physics Letters A

A general scheme for the effective-mass schrödinger equation and the generation of the associated potentials

The complete dynamic epitaxy of α-quartz during barium ion implantation is discussed. The nonimplanted sample is characterized by a very weak and broad peak at 2 electron volt in the red region. The Barium can be incorporated via dynamic SPEG in single-crystalline α-quartz hardly affecting the crystalline structure. The results show that the visible and ultraviolet peaks occurs at 2.42, 2.79, 3.4 and 4.2 electron volt respectively.

Applied Physics Letters

Cathodoluminescence versus dynamical epitaxy of Ba-ion irradiated alpha;-quartz

In this paper we present the accelerated reliability testing of MgZnO based UV detectors. The UV detectors are fabricated on glass, quartz and sapphire substrates by Pulsed Laser Deposition (PLD) technique. The films are highly oriented and show sharp transmission at 350nm and 330nm for Mg composition of 10% and 20% in ZnO, respectively. The device response has been studied and life expectancy of the devices has been estimated from the accelerated tests.

Materials Research Society Symposium - Proceedings

Accelerated reliability test inputs in analyzing the device response of MgZnO based UV detector

The optical band gap (Eg) of Pb1-xFexS solution-grown nanoparticle films was varied from 2.65 to 2.22 eV with an increase in iron concentration 0.25 ≤ × ≤ 0.75 in films grown at fixed pH and temperature by the chemical bath deposition method. The presence of excitonic structure in the ternary Pb1-xFexS for x ≥ 0.50 suggests increasing binding energy with increase in iron concentration in the films. A shift of excitonic peak towards higher energy with an increase in iron concentration is also observed.