R. Chandramohan

Preparation and characterization of Mn-doped ZnS nanoparticles

Mn-doped ZnS nanoparticles are synthesized by simple and cost effective chemical precipitation method. This diluted magnetic semiconductor is characterized by various techniques such as energy dispersive X-ray analysis, scanning electron microscopy, X-ray diffraction, photoluminescence and UV–Vis spectroscopy. High purity of the sample is confirmed by energy dispersive X-ray analysis. Sub-micrometer nanocrystals are observed using scanning electron microscope. Hexagonal phase of the material is confirmed by X-ray diffraction studies, and the micro-structural properties such as grain size, strain, dislocation density and texture coefficient are examined. High value of texture coefficient indicates the well-crystalline nature of the material. The band gap, Urbach energy and steepness parameter are calculated from the absorption spectrum. The band gap is also calculated from photoluminescence. The Stokes’s shift, Urbach energy and steepness parameter are reported in the case of Mn-doped ZnS for the first time.

Effect of ‘Al’ concentration on spin-dependent resonant tunnelling in InAs/Ga1−yAlyAs symmetrical double-barrier heterostructures

The effect of ‘Al’ concentration on spin-dependent tunnelling in strained non-magnetic symmetric double-barrier semiconductor has been theoretically investigated. The separation between spin-up and spin-down components, barrier transparency, polarization efficiency and tunnelling lifetime were calculated using the transfer matrix approach. The separation between spin-up and spin-down resonances and tunnelling lifetime were reported for the first time in the case of InAs/Ga1−yAlyAs heterostructures for various ‘Al’ concentrations and for various barrier widths. Cent percentage polarization can be obtained in this strained non-magnetic double-barrier semiconductor even without any external field.

Preparation and Characterization of Mn Doped ZnO Nanorods

Mn doped ZnO nanorods were prepared by chemical precipitation method. The micro-structural and structural properties of the nanorods were calculated from the X-ray diffraction technique. The formed nanorods was seen in the scanning electron microscopy. The purity of the sample was confirmed by the energy dispersive X-ray analysis (EDX). The optical properties were studied using UV-Vis spectroscopy and photoluminescence. In the photoluminescence spectrum, the peaks due to recombination of free electrons, oxygen vacancy and intrinsic defects were observed. The magnetic properties were studied using vibrating sample magnetometer (VSM) and the paramagnetic nature of the material was confirmed.