We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite... more We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite thin films (Y1Mn1O3, Y0.95Mn1.05O3, Y1Mn0.99Ti0.01O3, and Y0.94Mn1.05Ti0.01O3) by scanning electron microscopy (SEM) in secondary electron emission mode with a small acceleration voltage. Using SEM at an acceleration voltage of 1.0 kV otherwise homogenous surface charging effects are reduced, polarization charges can be observed and polarization directions (±Pz) of the ferroelectric domains in the polycrystalline thin films can be identified. Thin films of different chemical composition have been deposited by pulsed laser deposition on Pt/SiO2/Si structures under otherwise same growth conditions. Using SEM it has been shown that different charged domain density networks are existing in polycrystalline yttrium manganite thin films.
The magnetooptical (MO) response of Ru/Py/Ta thin film stacks with 4, 8, and 17 nm thick Ni81Fe19... more The magnetooptical (MO) response of Ru/Py/Ta thin film stacks with 4, 8, and 17 nm thick Ni81Fe19 permalloy (Py) films on a SiO2/Si and a ZnO substrate was measured by vector magnetooptical generalized ellipsometry. The MO response from VMOGE was modelled using a 4 × 4 Mueller matrix algorithm. The wavelength-dependent, substrate-independent and thickness-independent complex MO coupling constant ( Q ) of Py in the Ru/Py/Ta thin film stacks was extracted by fitting Mueller matrix difference spectra in the spectral range from 300 nm to 1000 nm. Although the composition-dependent saturation magnetization of Ni x Fe1−x alloys (x = 0.0…1.0), e.g. of Ni81Fe19, is predictable from the two saturation magnetization end points, the MO coupling constant of Ni x Fe1−x is not predictable from the two Q end points. However, in a small alloy range (0.0
ABSTRACT We report a simple and detailed simulation based analysis of an experimental field (FE) ... more ABSTRACT We report a simple and detailed simulation based analysis of an experimental field (FE) emission image formed on a phosphor coated indium tin oxide (ITO)/glass plate due to electron emission from a multiwalled carbon nanotube (MWCNT) film. Emission intensity versus effective emissive area, number of CNTs present in the film contributing emission process and number density of CNTs are determined, which agrees well with experimental results. The FE parameters, like turn on fields, threshold fields are calculated. This analysis renders a unique way to analyze field emission data and supports the theoretical formulation to evaluate the best possible values of FE parameters.
ABSTRACT The field emission (FE) properties of nickel nanoparticles embedded in thin silica matri... more ABSTRACT The field emission (FE) properties of nickel nanoparticles embedded in thin silica matrix irradiated with 100MeV Auþ7 ions at various fluences are studied here. A large increase in FE current density is observed in the irradiated films as compared to their as deposited counterpart. The dependence of FE properties on irradiation fluence is correlated with surface roughness, density of states of valence band and size distribution of nanoparticles as examined with atomic force microscope, X-ray photoelectron spectroscopy, and grazing incidence small angle x-ray scattering. A current density as high as 0.48mA/cm2 at an applied field 15V/lm has been found for the first time for planar field emitters in the film irradiated with fluence of 5.0�1013 ions/cm2. This significant enhancement in the current density is attributed to an optimized size distribution along with highest surface roughness of the same. This new member of field emission family meets most of the requirements of cold cathodes for vacuum micro/nanoelectronic devices.
Abstract: We present a simple, compact and low–cost fibre optic refractive index sensor based on ... more Abstract: We present a simple, compact and low–cost fibre optic refractive index sensor based on core diameter mismatch. The sensor has been made by etching out the whole cladding and some portion of the core of a SM 600 fibre. The etched out portion of the fibre makes the device sensitive to the external refractive index. We have carried out simulation and experimental study on the performance of proposed refractive index sensor. A good agreement between simulated and experimental results has been obtained.
ABSTRACT The present study describes the development of a simple approach to stabilize polycrysta... more ABSTRACT The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum–cerium borides were synthesized using hydroxide precursors. These precursors (La1−xCex(OH)3, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 °C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La0.5Ce0.5B6 shows excellent field emission characteristics with high field enhancement factor of 4502.
Cerium hexaboride is a well-known material for the filaments of electron microscopes due to its f... more Cerium hexaboride is a well-known material for the filaments of electron microscopes due to its field emission properties (high brightness electron source) and its long service life. The synthesis of cerium hexaboride (and most other borides) normally requires very high ...
ABSTRACT The present study describes the controlled synthesis of lanthanum hexaboride nanostructu... more ABSTRACT The present study describes the controlled synthesis of lanthanum hexaboride nanostructures with efficient field emission properties. The synthesis is mediated by a nanostructured lanthanum hydroxide precursor, which is controlled by varying the capping agent and pH using a hydrothermal route. The effect of charge on the capping agent (surfactant) strongly affects the shape and size of the precursor (neutral surfactants lead to the formation of nanorods while a cationic surfactant results in the formation of particles). This precursor mediated route leads to lanthanum hexaboride nanostructures at much lower temperatures (500 °C lower than the conventional solid state route) and allows for variation of morphology of nanostructured films. Vertically aligned nanorods (30 nm × 200–400 nm), nanoparticles (25 nm) and sub-micron particles (0.2–0.25 microns) could be precisely obtained. Field emission studies of these vertically aligned nanorods show a very high field enhancement factor (4191), which is required for an efficient field emitter.
We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite... more We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite thin films (Y1Mn1O3, Y0.95Mn1.05O3, Y1Mn0.99Ti0.01O3, and Y0.94Mn1.05Ti0.01O3) by scanning electron microscopy (SEM) in secondary electron emission mode with a small acceleration voltage. Using SEM at an acceleration voltage of 1.0 kV otherwise homogenous surface charging effects are reduced, polarization charges can be observed and polarization directions (±Pz) of the ferroelectric domains in the polycrystalline thin films can be identified. Thin films of different chemical composition have been deposited by pulsed laser deposition on Pt/SiO2/Si structures under otherwise same growth conditions. Using SEM it has been shown that different charged domain density networks are existing in polycrystalline yttrium manganite thin films.
The magnetooptical (MO) response of Ru/Py/Ta thin film stacks with 4, 8, and 17 nm thick Ni81Fe19... more The magnetooptical (MO) response of Ru/Py/Ta thin film stacks with 4, 8, and 17 nm thick Ni81Fe19 permalloy (Py) films on a SiO2/Si and a ZnO substrate was measured by vector magnetooptical generalized ellipsometry. The MO response from VMOGE was modelled using a 4 × 4 Mueller matrix algorithm. The wavelength-dependent, substrate-independent and thickness-independent complex MO coupling constant ( Q ) of Py in the Ru/Py/Ta thin film stacks was extracted by fitting Mueller matrix difference spectra in the spectral range from 300 nm to 1000 nm. Although the composition-dependent saturation magnetization of Ni x Fe1−x alloys (x = 0.0…1.0), e.g. of Ni81Fe19, is predictable from the two saturation magnetization end points, the MO coupling constant of Ni x Fe1−x is not predictable from the two Q end points. However, in a small alloy range (0.0
ABSTRACT We report a simple and detailed simulation based analysis of an experimental field (FE) ... more ABSTRACT We report a simple and detailed simulation based analysis of an experimental field (FE) emission image formed on a phosphor coated indium tin oxide (ITO)/glass plate due to electron emission from a multiwalled carbon nanotube (MWCNT) film. Emission intensity versus effective emissive area, number of CNTs present in the film contributing emission process and number density of CNTs are determined, which agrees well with experimental results. The FE parameters, like turn on fields, threshold fields are calculated. This analysis renders a unique way to analyze field emission data and supports the theoretical formulation to evaluate the best possible values of FE parameters.
ABSTRACT The field emission (FE) properties of nickel nanoparticles embedded in thin silica matri... more ABSTRACT The field emission (FE) properties of nickel nanoparticles embedded in thin silica matrix irradiated with 100MeV Auþ7 ions at various fluences are studied here. A large increase in FE current density is observed in the irradiated films as compared to their as deposited counterpart. The dependence of FE properties on irradiation fluence is correlated with surface roughness, density of states of valence band and size distribution of nanoparticles as examined with atomic force microscope, X-ray photoelectron spectroscopy, and grazing incidence small angle x-ray scattering. A current density as high as 0.48mA/cm2 at an applied field 15V/lm has been found for the first time for planar field emitters in the film irradiated with fluence of 5.0�1013 ions/cm2. This significant enhancement in the current density is attributed to an optimized size distribution along with highest surface roughness of the same. This new member of field emission family meets most of the requirements of cold cathodes for vacuum micro/nanoelectronic devices.
Abstract: We present a simple, compact and low–cost fibre optic refractive index sensor based on ... more Abstract: We present a simple, compact and low–cost fibre optic refractive index sensor based on core diameter mismatch. The sensor has been made by etching out the whole cladding and some portion of the core of a SM 600 fibre. The etched out portion of the fibre makes the device sensitive to the external refractive index. We have carried out simulation and experimental study on the performance of proposed refractive index sensor. A good agreement between simulated and experimental results has been obtained.
ABSTRACT The present study describes the development of a simple approach to stabilize polycrysta... more ABSTRACT The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum–cerium borides were synthesized using hydroxide precursors. These precursors (La1−xCex(OH)3, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 °C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La0.5Ce0.5B6 shows excellent field emission characteristics with high field enhancement factor of 4502.
Cerium hexaboride is a well-known material for the filaments of electron microscopes due to its f... more Cerium hexaboride is a well-known material for the filaments of electron microscopes due to its field emission properties (high brightness electron source) and its long service life. The synthesis of cerium hexaboride (and most other borides) normally requires very high ...
ABSTRACT The present study describes the controlled synthesis of lanthanum hexaboride nanostructu... more ABSTRACT The present study describes the controlled synthesis of lanthanum hexaboride nanostructures with efficient field emission properties. The synthesis is mediated by a nanostructured lanthanum hydroxide precursor, which is controlled by varying the capping agent and pH using a hydrothermal route. The effect of charge on the capping agent (surfactant) strongly affects the shape and size of the precursor (neutral surfactants lead to the formation of nanorods while a cationic surfactant results in the formation of particles). This precursor mediated route leads to lanthanum hexaboride nanostructures at much lower temperatures (500 °C lower than the conventional solid state route) and allows for variation of morphology of nanostructured films. Vertically aligned nanorods (30 nm × 200–400 nm), nanoparticles (25 nm) and sub-micron particles (0.2–0.25 microns) could be precisely obtained. Field emission studies of these vertically aligned nanorods show a very high field enhancement factor (4191), which is required for an efficient field emitter.
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Papers by Rajkumar Patra