Mukannan Arivanandhan

Role of SDS surfactant concentrations on the structural, morphological, dielectric and magnetic properties of CoFe2O4 nanoparticles

In this work, we report on the preparation of sodium dodecyl sulfate (SDS) surfactant added cobalt ferrite (CoFe2O4) magnetic nanoparticles by a co-precipitation method at various concentrations (0.04, 0.08, 0.12, 0.16 and 0.20 M) of SDS. The formation of a single phase cubic spinel structure is confirmed by XRD analysis. FTIR study confirms the presence of Fe–O symmetrical stretching vibrations in the tetrahedral site. TEM images imply that the SDS surfactant significantly limits the agglomeration of CoFe2O4 nanoparticles. A dielectric study reveals that the SDS added CoFe2O4 has a higher dielectric constant than that of pure CoFe2O4 nanoparticles. Magnetic measurements showed the enhanced saturation magnetization (138.75 emu g−1), coercivity (775.69 Oe) and retentivity (60.23 emu g−1) for 0.08 M SDS added CoFe2O4 nanoparticles. Further, the results obtained in the present study suggest that the surfactant can significantly modify the size and morphology of the prepared CoFe2O4 nanoparticles.

Structural and magnetic properties of cobalt-doped iron oxide nanoparticles prepared by solution combustion method for biomedical applications

Cobalt-doped iron oxide nanoparticles were prepared by solution combustion technique. The structural and magnetic properties of the prepared samples were also investigated. The average crystallite size of cobalt ferrite (CoFe2O4) magnetic nanoparticle was calculated using Scherrer equation, and it was found to be 16±5 nm. The particle size was measured by transmission electron microscope. This value was found to match with the crystallite size calculated by Scherrer equation corresponding to the prominent intensity peak (311) of X-ray diffraction. The high-resolution transmission electron microscope image shows clear lattice fringes and high crystallinity of cobalt ferrite magnetic nanoparticles. The synthesized magnetic nanoparticles exhibited the saturation magnetization value of 47 emu/g and coercivity of 947 Oe. The anti-microbial activity of cobalt ferrite nanoparticles showed better results as an anti-bacterial agent. The affinity constant was determined for the nanoparticles, and the cytotoxicity studies were conducted for the cobalt ferrite nanoparticles at different concentrations and the results are discussed.

The impact of Ge codoping on the enhancement of photovoltaic characteristics of B-doped Czochralski grown Si crystal

The effect of Ge codoping on minority carrier lifetime in boron (B)-doped Czochralski-silicon (CZ-Si) crystals was investigated. The minority carrier lifetime increased from 110 to 176 µs as Ge concentration was increased from zero to 1 × 1020 cm−3 in B/Ge codoped CZ-Si crystals. Light-induced degradation (LID) experiments showed that B-doped CZ-Si degrades rapidly, while B/Ge codoped CZ-Si degrades more slowly. Moreover, the flow pattern defect (FPD) density of grown-in micro-defects (GMD) in as-grown B/Ge codoped CZ-Si decreased with increasing Ge concentration. From the infrared (IR) absorption studies, it was observed that the interstitial oxygen (Oi) concentration decreased as Ge concentration increased in the crystal. The suppressed LID effect in the B/Ge codoped CZ-Si appears to be related to the low concentration of B-O associated defects, possibly because Ge doping retards the Oi diffusion in addition to the low Oi concentration present (evidenced from IR studies). The mechanism by which the Ge c...

Growth of In x Ga 1− x Sb alloy semiconductor at the International Space Station (ISS) and comparison with terrestrial experiments

Background:InxGa1−xSb is an important material that has tunable properties in the infrared (IR) region and is suitable for IR-device applications. Since the quality of crystals relies on growth conditions, the growth process of alloy semiconductors can be examined better under microgravity (μG) conditions where convection is suppressed.Aims:To investigate the dissolution and growth process of InxGa1−xSb alloy semiconductors via a sandwiched structure of GaSb(seed)/InSb/GaSb(feed) under normal and μG conditions.Methods:InxGa1−xSb crystals were grown at the International Space Station (ISS) under μG conditions, and a similar experiment was conducted under terrestrial conditions (1G) using the vertical gradient freezing (VGF) method. The grown crystals were cut along the growth direction and its growth properties were studied. The indium composition and growth rate of grown crystals were calculated.Results:The shape of the growth interface was nearly flat under μG, whereas under 1G, it was highly concave with the initial seed interface being nearly flat and having facets at the peripheries. The quality of the μG crystals was better than that of the 1G samples, as the etch pit density was low in the μG sample. The growth rate was higher under μG compared with 1G. Moreover, the growth started at the peripheries under 1G, whereas it started throughout the seed interface under μG.Conclusions:Kinetics played a dominant role under 1G. The suppressed convection under μG affected the dissolution and growth process of the InxGa1−xSb alloy semiconductor.

Bulk Growth of InGaSb Alloy Semiconductor under Terrestrial Conditions: A Preliminary Study for Microgravity Experiments at ISS

As a preliminary experiment for the growth of InGaSb alloy crystals under microgravity at International Space Station (ISS), bulk crystal was grown under terrestrial condition using the same gradient heating furnace (GHF). Czochralski grown GaSb <111>B single crystal was used as a seed and feed crystals for the growth of InGaSb bulk crystals. During the growth, heat pulses were intentionally introduced periodically to create the growth striations. From the striations, the growth rate of the grown crystal was estimated. The results show that the growth rate was gradually increased from the beginning of the growth and became stable. On the other hand the In composition of the grown crystal decreased along the growth direction. From the In composition, the temperature gradient in the solution was estimated and it was almost the same of that fixed during the growth.

Investigation of directionally solidified InGaSb ternary alloys from Ga and Sb faces of GaSb(111) under prolonged microgravity at the International Space Station

InGaSb ternary alloys were grown from GaSb (111)A and B faces (Ga and Sb faces) under microgravity conditions on board the International Space Station by a vertical gradient freezing method. The dissolution process of the Ga and Sb faces of GaSb and orientation-dependent growth properties of InGaSb were analysed. The dissolution of GaSb(111)B was greater than that of (111)A, which was found from the remaining undissolved seed and feed crystals. The higher dissolution of the Sb face was explained based on the number of atoms at that face, and its bonding with the next atomic layer. The growth interface shape was almost flat in both cases. The indium composition in both InGaSb samples was uniform in the radial direction and it gradually decreased along the growth direction because of segregation. The growth rate of InGaSb from GaSb (111)B was found to be higher than that of GaSb (111)A because of the higher dissolution of GaSb (111)B.

Enhancement of saturation magnetization of NiO nanorods via microwave assisted route

Nickel oxide nanorods (NiO) have been synthesized successfully by microwave assisted method using CTAB as a surfactant. The cubic phase NiO nanorods have been examined from X-ray diffraction. Morphological studies reveals rod like nanostructures by scanning electron microscope. Optical studies have been performed by UV -Vis analysis and it reveals the blue shift due to quantum confinement effect. The ferromagnetic nature of NiO nanorods has been observed from vibrating sample magnetometer with enhanced saturation magnetization (1.2 emu/g) and this enhancement shows the suitability of this material for magnetic applications.

Room temperature ethanol sensing property of cubic nanostructure tungsten oxide (WO3)

The gas sensing property of Tungsten oxide (WO3) nanostructures films have been grown on indium tin oxide (ITO) coated glass substrates by thermal evaporation technique without vacuum and catalyst. Tungsten trioxide (WO3) powder has been used as a source material and then by subsequent O2/Ar flow rate. High density with uniform morphology WO3 film was obtained. Morphology and phase structure of the nanostructure film have been characterized by Scanning electron microscope (SEM), X-ray diffraction (XRD) and Laser Raman spectroscopy. The samples were investigated as resistive gas sensor of ethanol gases.

Alloy Semiconductor Crystal Growth Under Microgravity

Microgravity studies on the dissolution and crystallization of InxGa1‐xSb have been done using a sandwich combination of InSb and GaSb as the starting material using the Chinese recoverable satellite. The same type of experiment was performed under 1G gravity condition for comparison. From these experiments and the numerical simulation, it is found that the shape of the solid/liquid interface and composition profile in the solution was found to be significantly affected by gravity. GaSb seed was dissolved faster than GaSb feed even though the GaSb feed temperature was higher than that of GaSb seed temperature. These results clearly indicate that solute transport due to gravity affects dissolution and growth processes of alloy semiconductor bulk crystals.