M. Shobana

Bio: M. Shobana is an academic researcher. The author has contributed to research in topics: Band gap & Doping. The author has an hindex of 3, co-authored 5 publications receiving 58 citations.

Structural and Magnetic Properties of Ni Doped

Abstract: Nickel (Ni) doped SnO2 powder samples were prepared using solid-state reaction with dopant concentrations in the range of 3 at.% to 15 at.%. The influence of Ni doping on structural, optical, and magnetic properties of the powder samples has been investigated. All the Ni doped powder samples exhibited tetragonal structure of SnO2. A decrease in optical band gap was observed with increase of Ni doping levels. The vibrating sample magnetometer measurements revealed that the Ni doped SnO2 powder samples were ferromagnetic at room temperature.

Effect of Substrate Temperature on Structural and Optical Properties of Nanocrystalline CdTe Thin Films Deposited by Electron Beam Evaporation

Abstract: Nanocrystalline Cadmium Telluride (CdTe) thin films were deposited onto glass substrates using electron beam evaporation technique. The effect of substrate temperature on the structural, morphological and optical properties of CdTe thin films has been investigated. All the CdTe films exhibited zinc blende structure with (111) preferential orientation. The crystallite size of the films increased from 35 nm to 116 nm with the increase of substrate temperature and the band gap of the films decreased from 2.87 eV to 2.05 eV with the increase of the crystallite size.

Structural, Optical, and Magnetic Properties of Co Doped CdTe Alloy Powders Prepared by Solid-State Reaction Method

Abstract: Co doped CdTe powder samples were prepared by solid-state reaction method In the present work effect of Co doping on structural, optical, and magnetic properties has been studied X-ray diffraction studies confirm zinc blend structure for all the samples The lattice parameter showed linear increase with the increase in Co content The elemental constituents were characterized by EDAX Optical studies showed the increase in band gap with increase in Co level The samples were diluted magnetic semiconductors and exhibited clear hysteresis loop showing room temperature ferromagnetism as confirmed by vibrating sample magnetometer

Structural, Optical and Magnetic properties of Cu doped ZnSe powders

Abstract: Cu doped ZnSe powder samples were prepared via solid-state reaction route. In the present study the effect of Cu doping on structural, optical and magnetic properties has been explored. X-ray diffra ction studies confirmed the formation of cubic phase in a ll the samples. Optical studies showed that with th e increase of Cu concentration, the band gap of the samples al so increased. The Cu doped ZnSe samples exhibited ferromagnetism at room temperature and proved Cu doped ZnSe samples are diluted magnetic semiconductors. Keywords : Solid state reaction, X-ray diffraction, Optical s tudies, Room temperature ferromagnetism, Cu doped ZnSe.

Structural, Optical and Magnetic properties of Co doped CdSe powders

Abstract: Co doped CdSe powder samples were prepared via solid-state reaction route. In the present study the effect of Co doping on structural, optical and magnetic properties has been studied. X-ray diffrac tion studies showed the formation of hexagonal phase of wurtzite structure for all the samples. Optical studies sho wed an increase in the band gap with increasing Co concent ration. Magnetization measurements showed a hysteresis loop and confirmed room temperature ferromagnetism in Co doped CdSe powders.

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

Abstract: This work reports the study concerning the structure and magnetic properties of undoped CeO2 and Fe-doped CeO2 (Ce1 xFexO2, 0.01 � x � 0.07) nanospheres with diameters of 100�200 nm prepared by hydrothermal method using polyvinylpyrrolidone (PVP) as surfactant. The prepared samples were studied by using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray absorption near-edge structure (XANES), and vibrating sample magnetometry (VSM). The XRD results showed that Fe-doped CeO2 was single-phased with a cubic structure, and with Fe 3+ successfully substituting in Ce 4+ sites. Raman spectra showed a redshift of F2g mode that caused by the Fe doping. The samples of both undoped CeO2 and Fe-doped CeO2 exhibited room temperature ferromagnetism, and the saturated magnetization (Ms) increased with increasing Fe content until x = 0.05, and then the samples displayed ferromagnetic loops as well as paramagnetic behavior. The roles of Ce 3+ and Fe 3+ spin electrons are discussed for the ferromagnetism in the Fe-doped CeO2.

Enhanced room temperature ferromagnetism in Ni doped SnO2 nanoparticles: A comprehensive study

Abstract: We emphasized on a detailed investigation of the structural, optical, and magnetic properties of pure and Ni-doped SnO2 nanoparticles (NPs) synthesized by a sol-gel process. An extensive structural study has been carried out using various characterization techniques. The X-ray Diffraction (XRD) spectra show the formation of the single phase tetragonal structure of pure and Ni-doped SnO2 NPs without any noticeable impurity phase such as NiO. XRD results indicate that the crystallite size of SnO2 is found to be decreased with Ni doping, which has also been confirmed by the Field Emission Scanning Electron Microscopy study. X-ray Photoelectron Spectroscopy (XPS) measurements displayed a clear sign for Ni2+ ions occupying the lattice sites of Sn4+ in the SnO2 host which also gives clear evidence for the formation of single phase Sn1-xNixO2 NPs. The optical analysis shows a significant decrease in the energy gap of SnO2, i.e., (from 3.71 eV to 3.28 eV) as Ni concentration increases which may be correlated with...

Preparation and microwave absorption properties of multi-walled carbon nanotubes decorated with Ni-doped SnO2 nanocrystals

Abstract: In this work, Ni-doped SnO2@MWCNTs composites were synthesized by a facile one-step hydrothermal method. The morphology and structure of the as-prepared composites were characterized by XRD, SEM, TEM, XPS, FT-IR and Raman. It was found that the SnO2 nanoparticles were successfully anchored on the MWCNTs with a diameter of 3–5 nm and Ni2+ was successfully doped into the SnO2@MWCNTs. Moreover, the effect of the doped Ni molar percentage on the electromagnetic parameters and microwave absorbing properties of the Ni-doped SnO2@MWCNTs composites was studied in the 2–18 GHz frequency range. The results showed that the composites with 28.2% doped Ni content exhibited the best microwave absorbing properties. The maximum RL reached −39.2 dB at 8.2 GHz with a thickness of 2.5 mm, and the bandwidth of RL lower than −10 dB was 3.6 GHz (from 12.6 to 16.2 GHz) with a thickness of 1.5 mm. The excellent microwave absorbing properties could be attributed to the good impedance match, Debye relaxation, interfacial polarization and high conductivity of the MWCNTs component. It was believed that the Ni-doped SnO2@MWCNTs composites could be used as a new type of microwave absorbing materials against electromagnetic pollution.

Thermal evolution of physical properties of vacuum evaporated polycrystalline CdTe thin films for solar cells

Abstract: This paper reports the change in optical, structural, morphological and electrical properties of CdTe thin films with post-deposition thermal treatment in air atmosphere. The polycrystalline cadmium telluride (CdTe) thin films of thickness 850 nm were deposited on glass and ITO coated glass substrates by thermal vacuum evaporation technique followed by annealing at different temperature 150, 250 and 350 °C. The physical properties have been investigated using characterization tools like UV–Vis spectrophotometer, X-ray diffraction, scanning electron microscopy coupled with EDS and source meter. The optical transmittance was observed to increase with post-deposition heat treatment which revealed the systematic reduction in optical energy band gap from 1.78 to 1.54 eV. The Swanepoel and Herve–Vandamme models as well as the dielectric theory were used to calculate various optical and dielectric constants. The thermal annealing enhances the crystallinity (zinc blende cubic structure) of films with preferred orientation (111). A number of crystallographic parameters were also evaluated and studied in depth with heat treatment. The surface morphology studies indicate that the films are homogeneous, densely packed, uniform and free from crystal defects. The current–voltage measurements exhibited ohmic behavior and the conductivity was found to increase with annealing temperature.