Satyabrata Mohapatra
Abstract
We report on the gettering behavior of Au at end-of-range (EOR) defects in float-zone grown Si(111), implanted with 1.5 MeV Au 2+ ions at room temperature. The effects of implantation dose and annealing temperature on the thermal evolution of gettering behavior of EOR defects have been investigated using ...
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We report on the gettering behavior of Au at end-of-range (EOR) defects in float-zone grown Si(111), implanted with 1.5 MeV Au 2+ ions at room temperature. The effects of implantation dose and annealing temperature on the thermal evolution of gettering behavior of EOR defects have been investigated using Rutherford backscattering spectrometry, while the microstructural evolution of Au implanted Si(111) has been studied using cross-sectional transmission electron microscopy combined with high resolution transmission electron microscopy. The gettering efficiency of EOR defects, comprising of dislocation loops, has been found to increase with increase in implantation dose up to 1.2 x 10 15 ions cm -2 , beyond which it was found to saturate at about 5 x 10 14 atoms cm -2 for annealing at 850 o C. We have observed that the gettering efficiency of the EOR defects for Au increased with increase in annealing temperature and reached 9 x 10 14 atoms cm -2 for annealing at 950 o C. The observed enhanced gettering efficiency of EOR defects is very promising for gettering applications in Si devices.
Jaspal Singh; Kavita Sahu; Sini Kuriakose; Nishant Tripathi; D. K. Avasthi; Satyabrata Mohapatra
Abstract
Nanostructured TiO2 thin films with highly enhanced photocatalytic activity were prepared by atom beam sputtering technique. The effects of thermal annealing on the structural, morphological and photocatalytic properties of TiO2 thin films were investigated using X-ray diffraction, atomic force microscopy, ...
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Nanostructured TiO2 thin films with highly enhanced photocatalytic activity were prepared by atom beam sputtering technique. The effects of thermal annealing on the structural, morphological and photocatalytic properties of TiO2 thin films were investigated using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, Raman spectroscopy and UV-visible absorption spectroscopy. X-ray diffraction studies showed that the as-deposited TiO2 thin films made up of anatase TiO2 nanoparticles transformed into anatase/ rutile mixed-phase TiO2 nanoparticles upon annealing. Field emission scanning electron microscopy and atomic force microscopy studies revealed growth of TiO2 nanoparticles from 16 nm to 29 nm upon annealing at 600 o C. The photocatalytic activities of the nanostructured TiO2 thin films were studied by monitoring photocatalytic degradation of methylene blue in water. Our results showed that the as-deposited nanostructured TiO2 thin films exhibited highly enhanced photocatalytic efficiency as compared to the annealed samples. The mechanism underlying the enhanced photocatalytic activity of nanostructured TiO2 thin film is tentatively proposed.
Sini Kuriakose; Biswarup Satpati; Satyabrata Mohapatra
Abstract
ZnO nanostructures were synthesized by a facile wet chemical method using water, ethanol and propanol as solvents. X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been used to study the structural properties of the synthesized ZnO ...
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ZnO nanostructures were synthesized by a facile wet chemical method using water, ethanol and propanol as solvents. X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been used to study the structural properties of the synthesized ZnO nanostructures, while their optical properties have been studied using UV-visible absorption spectroscopy and Raman spectroscopy. The photocatalytic activities of the as-synthesized ZnO nanostructures were evaluated by monitoring sunlight driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water and it was observed that ZnO nanostructures prepared using propanol as a solvent exhibit highly enhanced photocatalytic activity as compared to those prepared using other solvents. The mechanism underlying the photocatalytic activity of ZnO nanostructures towards photocatalytic degradation of dyes is proposed. We attribute the highly enhanced photocatalytic activity of ZnO nanostructures prepared in propanol to the high surface area of nanosheets-like structures formed, which lead to enhanced adsorption of dye molecules resulting in efficient photocatalytic degradation of dyes upon sunlight irradiation.
Jaspal Singh; Satyabrata Mohapatra
Abstract
Nanostructures of TiO2 were synthesized by a facile sol-gel method using pentanol as solvent. The effects of thermal annealing on the structural, optical and photocatalytic properties of as-synthesized TiO2 nanostructures have been studied using X-ray diffraction (XRD), atomic force microscopy (AFM), ...
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Nanostructures of TiO2 were synthesized by a facile sol-gel method using pentanol as solvent. The effects of thermal annealing on the structural, optical and photocatalytic properties of as-synthesized TiO2 nanostructures have been studied using X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy and UV-visible absorption spectroscopy. XRD and Raman spectroscopy results revealed that the synthesized TiO2 nanostructures exist in anatase phase for annealing at temperatures up to 300 o C, while annealing at 600 o C led to the formation of TiO2 nanostructures in anatase/rutile mixed-phase. AFM studies revealed the presence of TiO2 nanorods, which showed a small decrease in aspect ratio upon annealing. The photocatalytic activity of nanostructured TiO2 samples was evaluated through sun light driven degradation of methylene blue (MB) dye in water. TiO2 nanorods in anatase/rutile mixed-phase in the sample annealed at 600 o C were found to exhibit the highest photocatalytic activity towards degradation of MB dye. The mechanism underlying the enhanced photocatalytic activity of TiO2 nanostructures in anatase/rutile mixed-phase is tentatively proposed.
Sini Kuriakose; Biswarup Satpati; Satyabrata Mohapatra
Abstract
Highly photocatalytically active nanodisks of ZnO and Co doped ZnO were synthesized by a facile wet chemical method. The structural, optical and photocatalytic properties of ZnO and Co doped ZnO nanodisks were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic ...
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Highly photocatalytically active nanodisks of ZnO and Co doped ZnO were synthesized by a facile wet chemical method. The structural, optical and photocatalytic properties of ZnO and Co doped ZnO nanodisks were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and UV-visible absorption spectroscopy. FESEM, AFM and TEM studies revealed the presence of ZnO nanodisks. Sun light driven degradation of aqueous methyl orange (MO) dye was used for evaluating the photocatalytic activity of as-synthesized ZnO and Co doped ZnO nanodisks. Co doped ZnO nanodisks showed very high photocatalytic efficiency and lead to almost complete degradation of MO dye in just 8 minutes. A tentative mechanism of the photocatalytic degradation of MO by Co doped ZnO nanodisks is proposed. We attribute the enhanced photocatalytic activity of Co doped ZnO nanodisks to their high specific surface area and efficient charge carrier separation due Co doping, which improves suppression of recombination of photogenerated electrons and holes. Development of sun light active highly efficient and stable photocatalysts is very promising for environmental remediation leading to safe and clean water.
Bandita Mohapatra; Reena Kaintura; Jaspal Singh; Sini Kuriakose; Satyabrata Mohapatra
Abstract
Stable aqueous dispersions with high concentration of silver nanoparticles were synthesized by a facile and green synthetic route by treating silver ions with aqueous Citrus limon extract, used as a reducing and capping agent. The formation and growth of silver nanoparticles, prepared by this simple ...
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Stable aqueous dispersions with high concentration of silver nanoparticles were synthesized by a facile and green synthetic route by treating silver ions with aqueous Citrus limon extract, used as a reducing and capping agent. The formation and growth of silver nanoparticles, prepared by this simple and convenient method, was monitored using UV-visible absorption spectroscopy. The effects of Ag concentration, Citrus limon extract concentration, in-situ and ex-situ pH variations upon NaOH addition on the structural, optical and plasmonic properties of the synthesized Ag nanoparticles were investigated. X-ray diffraction studies revealed the formation of Ag nanoparticles, whose morphology was studied using atomic force microscopy. UV-visible absorption studies revealed surface plasmon resonance (SPR) peak around 465 nm, confirming the presence of Ag nanoparticles. The SPR peak blue shifted along with significant enhancement in intensity with increase in Ag concentration and pH, due to the growth and increased aggregation of Ag nanoparticles. We have shown that addition of NaOH is a key to rapid biosynthesis of stable aqueous dispersions of high concentration of silver nanoparticles. This green synthetic route provides faster synthesis of silver nanoparticles with improved colloidal stability, which can be used in foods, cosmetics and biomedical applications.
Neha Bhardwaj; Satyabrata Mohapatra
Abstract
Three dimensional (3D) complex microcrystal chains of SnO2 have been fabricated by simple carbothermal reduction based vapour deposition method. The structural and optical properties of the as-synthesized materials were well characterized by field emission scanning electron microscopy (FESEM) with energy ...
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Three dimensional (3D) complex microcrystal chains of SnO2 have been fabricated by simple carbothermal reduction based vapour deposition method. The structural and optical properties of the as-synthesized materials were well characterized by field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), Raman spectroscopy and photoluminescence spectroscopy. FESEM studies revealed the formation of 3D complex chains of microcrystals of SnO2 of varying shape and size. The SnO2 microcrystals have been found to be inter-connected through oriented attachment, leading to the formation of 3D complex chains of microcrystals. XRD studies showed the presence of SnO2 and Sn in the synthesized material. Photoluminescence studies on SnO2 microcrystal chains revealed peaks at 361, 407, 438 and 465 nm. A tentative mechanism of formation of the 3D complex chains of SnO2 microcrystals is proposed. These SnO2 microcrystal chains have potential applications as building blocks in novel functional devices.
