Nidhi Sinha - Academia.edu (original) (raw)
Papers by Nidhi Sinha
Thin Solid Films, 2006
We report on the preparation and structural characterization of piezoelectric films of aluminium ... more We report on the preparation and structural characterization of piezoelectric films of aluminium nitride onto diamond substrates. The samples were fabricated by sequential radio frequency reactive diode sputtering processes, carried out at various temperatures, in a head vacuum system starting from stechiometric targets. The structural characterization of the films was performed by energy dispersive X-ray diffraction analysis. The deposition temperature was found to play a relevant role to obtain highly textured films with the c-axis perpendicular to the substrate surface, as required by surface-acoustic-wave applications. In particular, a minimum substrate temperature of 300 °C was needed in order to obtain any internal order along the c-axis while, increasing the temperature, the AlN orientation becomes preferential. The rocking curve analysis revealed a good crystalline quality of the AlN films whose degree of epitaxy can be well described by a linearly increasing function of the temperature at which the films are grown.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Journal of Crystal Growth, 2008
Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was... more Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was successfully grown from aqueous solution for the first time by slow evaporation method. The solubility of LHA was determined in water and good optical quality single crystal of dimensions up to 21 · 13 · 9 mm 3 was obtained. The grown crystals were characterized by X-ray diffraction, FTIR, UV-Vis-NIR, microhardness and DTA/TGA studies. The SHG efficiency is found to be higher than that of KDP crystal. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and the results are discussed. Photoconductivity studies of LHA reveal its positive photoconducting nature.
Physica B-condensed Matter, 2011
New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application wa... more New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Single crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency ($95%) with large band gap (4.57 eV) was analyzed by UV-vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 C) and melting point (242 C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].
Journal of Applied Physics, 2011
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2.36×1019 per cm3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Physics and Chemistry of Solids, 2010
Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the pres... more Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the presence of maleic acid by a slow evaporation technique. The structural parameters were determined using powder X-ray diffraction (XRD) and found to have monoclinic symmetry (space group P2 1 /m) with a ¼ 9.902, b ¼ 17.510, c ¼5.555Å and a¼g¼901, b¼96.461. The transparency and optical analysis were carried out using UV-vis analysis. The optical band gap is found to be 4.71 eV. The presence of various functional groups was confirmed by FTIR analysis. The samples have shown piezoelectric behavior with a fairly good piezoelectric charge coefficient (d 33 ) of 5 pC/N, when it is poled at 7 kV/cm. The hysteresis loop was plotted and the remnant polarization and coercive field were found to be 2.8 mC/cm 2 and 4 kV/cm, respectively. The dielectric analysis was carried out as a function of temperature at various frequencies and the results were also discussed.
Crystal Research and Technology, 2009
Single crystals of L-histidine tetrafluoroborate (C 6 H 10 N 3 O 2 BF 4, L-HFB) were grown by sol... more Single crystals of L-histidine tetrafluoroborate (C 6 H 10 N 3 O 2 BF 4, L-HFB) were grown by solution growth method using two different temperature profiles: conventional, in which the growth temperature was kept constant at 30 °C and rapid, in which it was increased in steps of 1 K per day while keeping the other growth conditions same. Crystals grew in nearly 30 and 10 days in the two methods, respectively. The crystals were transparent and showing its characteristic morphology. Both types of crystals were characterized by XRD for their structural comparison. Surface morphology and growth features of the crystals were studied by SEM. Features of two dimensional layer growth steps, rectangular etch pits, slip lines and bands, etc. were observed. The presence of various functional groups and their bonding were studied by FTIR in the range 4000-400 cm -1 . Thermal stability of the crystals was determined by thermo-gravimetric and differential thermal analysis. The generation of green light due to second harmonic generation for fundamental λ = 1064 nm has been confirmed in both cases. Dielectric constant measurement was carried out in the range 20 Hz-2 MHz. In the UV-Vis studies, high transmittance and a shorter 'lower cut off' value (232 nm) were observed. The effect of rapid growth on the structural, morphological and optical properties of the crystals were studied and compared to those of crystals grown in conventional way.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Materials Letters, 2010
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2:36 Â 10 19 per cm 3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Crystal Growth, 2008
Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was... more Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was successfully grown from aqueous solution for the first time by slow evaporation method. The solubility of LHA was determined in water and good optical quality single crystal of dimensions up to 21 · 13 · 9 mm 3 was obtained. The grown crystals were characterized by X-ray diffraction, FTIR, UV-Vis-NIR, microhardness and DTA/TGA studies. The SHG efficiency is found to be higher than that of KDP crystal. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and the results are discussed. Photoconductivity studies of LHA reveal its positive photoconducting nature.
Integrated Ferroelectrics, 2010
Flower like & Urchin-like ZnO nanorods were grown along two different growth directions (002) and... more Flower like & Urchin-like ZnO nanorods were grown along two different growth directions (002) and (100) by a simple low temperature solution technique using NaOH and KOH. The products were characterized with scanning electron microscopy, X-ray powder diffraction, UV-Vis spectrometer and Impedance analyzer. In the temperature variation of dielectric constant a ferroelectric phase transition at 343 K was observed at 1 KHz in ZnO: KOH while no phase transition was observed in ZnO:NaOH. In piezoelectric characterization, the piezoelectric charge coefficient (d33) was measured and slight variations in absorption edge cutoff were found in UV spectra in both the ZnO samples.
Physica B-condensed Matter, 2011
New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application wa... more New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Single crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency ($95%) with large band gap (4.57 eV) was analyzed by UV-vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 C) and melting point (242 C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].
![Research paper thumbnail of Flux growth and low temperature dielectric relaxation in piezoelectric Pb[(Zn 1/3 Nb 2/3 ) 0.91 Ti 0.09 ]O 3 single crystals](https://attachments.academia-assets.com/48541393/thumbnails/1.jpg)
](Crystal Research and Technology, 2009
Single crystals of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) have been grown by flux method after ... more Single crystals of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) have been grown by flux method after modifications in temperature profile, flux ratio and addition of excess ZnO/B2O3 which resulted in enhanced perovskite yield (more than 95%). Only a few crystals showed the presence of pyrochlore phase/variation in composition. A comparative characterization of these crystals were carried out in respect of piezoelectric charge coefficient d33, dielectric constant, ac conductivity and hysteresis loop after cutting and poling the crystals along [001] direction. The total activation energy for conduction has been found to increase with Ti-content in the sample. The effect of ZnO on growth behavior has been analyzed. A detailed analysis of PZNT (91:9) has been carried out at low temperature in respect of the various thermodynamic parameters related to the dielectric relaxation mechanism, like optical dielectric constant, static dielectric constant, free energy of activation for dipole relaxation, enthalpy of activation and relaxation time, have been calculated in the vicinity of transition temperature in the lower temperature region. The activation energy for relaxation at -10 and -49 °C have been found to be 0.09 and 0.02 eV respectively. The results were analyzed and a detailed dielectric analysis and low temperature relaxation behavior of PZNT crystals were interpreted. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Journal of Applied Physics, 2011
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2.36×1019 per cm3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Crystal Growth, 2009
Crystal Research and Technology, 2005
Undoped and PbI2-doped dendritic single crystals were grown by vapour growth technique. The basal... more Undoped and PbI2-doped dendritic single crystals were grown by vapour growth technique. The basal surfaces of the as grown crystals were examined by optical and electron microscopy to observe wide variety of growth and defect features. Apart from typical features of dendritic growth, features of overgrowth, slip bands, growth steps and their bunching, etc. were observed. The basal surfaces of the crystals were then etched by controlled condensation of water vapour, after optimizing the etching condition, and the microscopic studies were repeated. Etch pits of hexagonal and triangular shape, both symmetric and asymmetric, and of different density, were observed in the case of undoped and doped crystals, respectively. In some cases, crystallographic hillocks were also observed. The crystals were also examined by X-ray diffraction for their polytypism and related behaviour. The results are analyzed to elicit information on the correlation of structure, defects and surface features of the crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Journal of Physics and Chemistry of Solids, 2010
Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the pres... more Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the presence of maleic acid by a slow evaporation technique. The structural parameters were determined using powder X-ray diffraction (XRD) and found to have monoclinic symmetry (space group P2 1 /m) with a ¼ 9.902, b ¼ 17.510, c ¼5.555Å and a¼g¼901, b¼96.461. The transparency and optical analysis were carried out using UV-vis analysis. The optical band gap is found to be 4.71 eV. The presence of various functional groups was confirmed by FTIR analysis. The samples have shown piezoelectric behavior with a fairly good piezoelectric charge coefficient (d 33 ) of 5 pC/N, when it is poled at 7 kV/cm. The hysteresis loop was plotted and the remnant polarization and coercive field were found to be 2.8 mC/cm 2 and 4 kV/cm, respectively. The dielectric analysis was carried out as a function of temperature at various frequencies and the results were also discussed.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Materials Letters, 2009
Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Z... more Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Zn 2+ /OH − ratio. The morphology and structural studies confirmed the formation of nano structure, revealing the [0001] oriented growth of the ZnO nanorods. The variation of ...
Thin Solid Films, 2006
We report on the preparation and structural characterization of piezoelectric films of aluminium ... more We report on the preparation and structural characterization of piezoelectric films of aluminium nitride onto diamond substrates. The samples were fabricated by sequential radio frequency reactive diode sputtering processes, carried out at various temperatures, in a head vacuum system starting from stechiometric targets. The structural characterization of the films was performed by energy dispersive X-ray diffraction analysis. The deposition temperature was found to play a relevant role to obtain highly textured films with the c-axis perpendicular to the substrate surface, as required by surface-acoustic-wave applications. In particular, a minimum substrate temperature of 300 °C was needed in order to obtain any internal order along the c-axis while, increasing the temperature, the AlN orientation becomes preferential. The rocking curve analysis revealed a good crystalline quality of the AlN films whose degree of epitaxy can be well described by a linearly increasing function of the temperature at which the films are grown.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Journal of Crystal Growth, 2008
Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was... more Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was successfully grown from aqueous solution for the first time by slow evaporation method. The solubility of LHA was determined in water and good optical quality single crystal of dimensions up to 21 · 13 · 9 mm 3 was obtained. The grown crystals were characterized by X-ray diffraction, FTIR, UV-Vis-NIR, microhardness and DTA/TGA studies. The SHG efficiency is found to be higher than that of KDP crystal. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and the results are discussed. Photoconductivity studies of LHA reveal its positive photoconducting nature.
Physica B-condensed Matter, 2011
New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application wa... more New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Single crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency ($95%) with large band gap (4.57 eV) was analyzed by UV-vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 C) and melting point (242 C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].
Journal of Applied Physics, 2011
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2.36×1019 per cm3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Physics and Chemistry of Solids, 2010
Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the pres... more Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the presence of maleic acid by a slow evaporation technique. The structural parameters were determined using powder X-ray diffraction (XRD) and found to have monoclinic symmetry (space group P2 1 /m) with a ¼ 9.902, b ¼ 17.510, c ¼5.555Å and a¼g¼901, b¼96.461. The transparency and optical analysis were carried out using UV-vis analysis. The optical band gap is found to be 4.71 eV. The presence of various functional groups was confirmed by FTIR analysis. The samples have shown piezoelectric behavior with a fairly good piezoelectric charge coefficient (d 33 ) of 5 pC/N, when it is poled at 7 kV/cm. The hysteresis loop was plotted and the remnant polarization and coercive field were found to be 2.8 mC/cm 2 and 4 kV/cm, respectively. The dielectric analysis was carried out as a function of temperature at various frequencies and the results were also discussed.
Crystal Research and Technology, 2009
Single crystals of L-histidine tetrafluoroborate (C 6 H 10 N 3 O 2 BF 4, L-HFB) were grown by sol... more Single crystals of L-histidine tetrafluoroborate (C 6 H 10 N 3 O 2 BF 4, L-HFB) were grown by solution growth method using two different temperature profiles: conventional, in which the growth temperature was kept constant at 30 °C and rapid, in which it was increased in steps of 1 K per day while keeping the other growth conditions same. Crystals grew in nearly 30 and 10 days in the two methods, respectively. The crystals were transparent and showing its characteristic morphology. Both types of crystals were characterized by XRD for their structural comparison. Surface morphology and growth features of the crystals were studied by SEM. Features of two dimensional layer growth steps, rectangular etch pits, slip lines and bands, etc. were observed. The presence of various functional groups and their bonding were studied by FTIR in the range 4000-400 cm -1 . Thermal stability of the crystals was determined by thermo-gravimetric and differential thermal analysis. The generation of green light due to second harmonic generation for fundamental λ = 1064 nm has been confirmed in both cases. Dielectric constant measurement was carried out in the range 20 Hz-2 MHz. In the UV-Vis studies, high transmittance and a shorter 'lower cut off' value (232 nm) were observed. The effect of rapid growth on the structural, morphological and optical properties of the crystals were studied and compared to those of crystals grown in conventional way.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Materials Letters, 2010
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2:36 Â 10 19 per cm 3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Crystal Growth, 2008
Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was... more Bulk single crystals of L-histidine acetate dihydrate (LHA), a new organic nonlinear material was successfully grown from aqueous solution for the first time by slow evaporation method. The solubility of LHA was determined in water and good optical quality single crystal of dimensions up to 21 · 13 · 9 mm 3 was obtained. The grown crystals were characterized by X-ray diffraction, FTIR, UV-Vis-NIR, microhardness and DTA/TGA studies. The SHG efficiency is found to be higher than that of KDP crystal. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and the results are discussed. Photoconductivity studies of LHA reveal its positive photoconducting nature.
Integrated Ferroelectrics, 2010
Flower like & Urchin-like ZnO nanorods were grown along two different growth directions (002) and... more Flower like & Urchin-like ZnO nanorods were grown along two different growth directions (002) and (100) by a simple low temperature solution technique using NaOH and KOH. The products were characterized with scanning electron microscopy, X-ray powder diffraction, UV-Vis spectrometer and Impedance analyzer. In the temperature variation of dielectric constant a ferroelectric phase transition at 343 K was observed at 1 KHz in ZnO: KOH while no phase transition was observed in ZnO:NaOH. In piezoelectric characterization, the piezoelectric charge coefficient (d33) was measured and slight variations in absorption edge cutoff were found in UV spectra in both the ZnO samples.
Physica B-condensed Matter, 2011
New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application wa... more New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Single crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency ($95%) with large band gap (4.57 eV) was analyzed by UV-vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 C) and melting point (242 C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].
Crystal Research and Technology, 2009
Single crystals of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) have been grown by flux method after ... more Single crystals of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) have been grown by flux method after modifications in temperature profile, flux ratio and addition of excess ZnO/B2O3 which resulted in enhanced perovskite yield (more than 95%). Only a few crystals showed the presence of pyrochlore phase/variation in composition. A comparative characterization of these crystals were carried out in respect of piezoelectric charge coefficient d33, dielectric constant, ac conductivity and hysteresis loop after cutting and poling the crystals along [001] direction. The total activation energy for conduction has been found to increase with Ti-content in the sample. The effect of ZnO on growth behavior has been analyzed. A detailed analysis of PZNT (91:9) has been carried out at low temperature in respect of the various thermodynamic parameters related to the dielectric relaxation mechanism, like optical dielectric constant, static dielectric constant, free energy of activation for dipole relaxation, enthalpy of activation and relaxation time, have been calculated in the vicinity of transition temperature in the lower temperature region. The activation energy for relaxation at -10 and -49 °C have been found to be 0.09 and 0.02 eV respectively. The results were analyzed and a detailed dielectric analysis and low temperature relaxation behavior of PZNT crystals were interpreted. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Journal of Applied Physics, 2011
Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-c... more Single crystalline p-type K-doped ZnO nanorods (NR) have been synthesized by convenient and low-cost solution technique. X-ray diffraction analysis confirmed the hexagonal system of K-doped ZnO nanorods and a preferred a axis orientation. The diameter and length were found to be 30-50 nm and 150-200 nm, respectively, in electron microscopic studies. The p-type nature and high hole density of 2.36×1019 per cm3 was demonstrated by Hall studies. A sharp lower cutoff and reduction in the bandgap was observed in UV-Vis study which is linked to its smaller size and p-type conduction in NR. In Photoluminescence studies, a near band emission in the UV range and a yellow emission with a blueshift were detected in the visible region in K-doped ZnO NR. The variation in intensity of peaks is correlated with the dimensions of NR. The redshift observed in Raman peaks is explained in terms of the stress developed in ZnO nanostructure due to lattice mismatch by K doping. These results provide better insight of K-doped ZnO nanostructures for both fundamental research and technological applications in optoelectronic devices.
Journal of Crystal Growth, 2009
Crystal Research and Technology, 2005
Undoped and PbI2-doped dendritic single crystals were grown by vapour growth technique. The basal... more Undoped and PbI2-doped dendritic single crystals were grown by vapour growth technique. The basal surfaces of the as grown crystals were examined by optical and electron microscopy to observe wide variety of growth and defect features. Apart from typical features of dendritic growth, features of overgrowth, slip bands, growth steps and their bunching, etc. were observed. The basal surfaces of the crystals were then etched by controlled condensation of water vapour, after optimizing the etching condition, and the microscopic studies were repeated. Etch pits of hexagonal and triangular shape, both symmetric and asymmetric, and of different density, were observed in the case of undoped and doped crystals, respectively. In some cases, crystallographic hillocks were also observed. The crystals were also examined by X-ray diffraction for their polytypism and related behaviour. The results are analyzed to elicit information on the correlation of structure, defects and surface features of the crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Journal of Physics and Chemistry of Solids, 2010
Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the pres... more Urea-succinic acid crystals have been grown at room temperature from aqueous solution in the presence of maleic acid by a slow evaporation technique. The structural parameters were determined using powder X-ray diffraction (XRD) and found to have monoclinic symmetry (space group P2 1 /m) with a ¼ 9.902, b ¼ 17.510, c ¼5.555Å and a¼g¼901, b¼96.461. The transparency and optical analysis were carried out using UV-vis analysis. The optical band gap is found to be 4.71 eV. The presence of various functional groups was confirmed by FTIR analysis. The samples have shown piezoelectric behavior with a fairly good piezoelectric charge coefficient (d 33 ) of 5 pC/N, when it is poled at 7 kV/cm. The hysteresis loop was plotted and the remnant polarization and coercive field were found to be 2.8 mC/cm 2 and 4 kV/cm, respectively. The dielectric analysis was carried out as a function of temperature at various frequencies and the results were also discussed.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Physica B-condensed Matter, 2011
Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation me... more Pure and ZnCl 2 doped anthracene (AN & ANZ) single crystals were grown by the slow evaporation method. In XRD studies a shift in peaks towards higher theta value and change in preferred orientation from (0 0 1) to (0 0 2) were observed as a result of doping. UV-vis spectra show a blueshift of various peaks in ANZ. Remarkable increases in dielectric constant and AC conductivity were observed along with a structure related phase transition at 40 1C in ANZ at atmospheric pressure itself. Good fluorescence properties with a strong green emission were observed in photoluminescence studies.
Materials Letters, 2009
Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Z... more Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Zn 2+ /OH − ratio. The morphology and structural studies confirmed the formation of nano structure, revealing the [0001] oriented growth of the ZnO nanorods. The variation of ...