Abstract We have deposited a large area (10 × 10 cm2) Sb-doped SnO2 (ATO) thin film transparent c... more Abstract We have deposited a large area (10 × 10 cm2) Sb-doped SnO2 (ATO) thin film transparent conducting electrode (TCE) using chemical spray pyrolysis method. The XRD analysis confirms tetragonal crystal structure of ATO thin film with significant preferred orientation. The XPS analysis clearly indicates the presence of Sb in +5 charge state when substituted into the SnO2 lattice. The UV–Vis transmittance spectra of the film showed average transmittance of 77.5% at 550 nm and the calculated direct band gap value was 3.82 eV. As-deposited ATO film exhibited lowest sheet resistivity and resistance of 6.715 × 10−4 Ω cm and 31.91 Ω/□ respectively due to Sb-dopant effect into the Sn lattice. Doping with Sb into SnO2 exhibits high carrier concentration of 7.899 × 1020 cm−3 and mobility of 28.45 cm2/Vs resulting in enhanced electrical transport properties. The variation of the sheet resistance of the large area deposited film is estimated across every 1 × 1 cm2 surface area. Variation of sheet resistance of the ATO film as a function of annealing temperature and duration was found to be appreciably stable. Kelvin probe study yielded a surface work function of 5.14 eV for the ATO film indicating the suitability to serve as an indium-free alternate TCE for optoelectronic device applications.
Journal of Atomic, Molecular, and Optical Physics, 2011
Bulk Zn0.95TM0.05O (TM=Cr, Mn, Fe, Co, and Ni) were synthesized by the standard ceramic method an... more Bulk Zn0.95TM0.05O (TM=Cr, Mn, Fe, Co, and Ni) were synthesized by the standard ceramic method and explored for variation in their band gap energies using Diffuse Reflectance Spectroscopy in the ultraviolet-visible region. Phase quantification and compositional studies were performed using Rietveld analysis of the X-Ray Diffraction patterns, Scanning Electron microscopy, and Energy Dispersive X-Ray Analysis. Due to 3d transition ion doping, the samples have brilliant colors, and the absorption edge of Zn0.95TM0.05O was found to shift towards the visible and ultraviolet-visible region. The blue and red shifts in band gaps observed for various transition metal ion-doped ZnO are discussed.
Non-local electrical properties of pulsed laser deposited La0.7Sr0.3MnO3/Bi2Sr2CaCu2O8/La0.7Sr0.3... more Non-local electrical properties of pulsed laser deposited La0.7Sr0.3MnO3/Bi2Sr2CaCu2O8/La0.7Sr0.3MnO3 (L-B-L) coplanar tri-layer is investigated under different wiring configurations. Long range super-current of Bi-2212 penetrating into LSMO is dependent on geometry of spin injection. From qualitative analysis of structural, magnetic and electrical data, long range super-current is suggested to pass through domain walls and/or grain boundaries of LSMO.
Transactions of the Indian Institute of Metals, 2011
Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis ... more Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to
ABSTRACT Undoped and lithium (Li) (1-5 wt%) doped MoO3 thin films were deposited over ITO coated ... more ABSTRACT Undoped and lithium (Li) (1-5 wt%) doped MoO3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325 °C. Undoped film was oriented along the <0 k 0> direction. The texture coefficient value of the undoped film was higher for the (0 2 0) plane compared to other planes of undoped and 'Li' doped films. The 100% peak (0 2 1) plane of orthorhombic MoO3 and hexagonal phase were induced upon doping with 'Li'. The crystallite size of the undoped film is less compared to the 'Li' doped films. The intense Raman peak at 996 cm-1 is due to the terminal oxygen (Mo6+ = O stretching mode) in the orthorhombic α-MoO3 phase. The characteristic Mo 3d5/2 and 3d3/2 doublet caused by spin-orbit coupling are clearly resolved with a splitting of 3.1 eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with 'Li' compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with 'Li' concentration. Cyclic voltammetry result shows that the presence of mixed phases in 'Li' doped films decreases the electrochemical performance. Transport study reveals that the carrier concentration and mobility of the 'Li' doped films are lower compared to the undoped film which is due to the evolution of hexagonal phase upon doping with 'Li'. A dye sensitized solar cell (DSSC) was fabricated using undoped MoO3 film as photoanode and its efficiency is calculated.
Advances in Materials Science and Engineering, 2010
Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic m... more Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, andα-Fe2O3having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also d...
ABSTRACT In this work, we report observation of two superconducting transitions and their respons... more ABSTRACT In this work, we report observation of two superconducting transitions and their response to an external field in pulsed laser deposited YBa2Cu3O7/La0.7Sr0.3MnO3/YBa2Cu3O7 (Y-L-Y) hetero-epitaxial tri-layer. Magnetization data of Y-L-Y tri-layer in “out-plane” geometry showed a single Meissner transition indicating superconductivity of the top and bottom YBa2Cu3O7 layers to be magnetically coupled. In contradiction, the magneto-transport data unusually showed two transition onsets Tcon1 and Tcon2 implying electrically decoupled superconductivity. The Tcon1 decreased systematically with field, whereas Tcon2 showed anomalous behavior with substantial increase in transition width due to the local stray field induced vortex states.
Hydrothermally synthesized mesoporous carbon coated SnO2 nanoparticles (NPs) with numerous oxygen... more Hydrothermally synthesized mesoporous carbon coated SnO2 nanoparticles (NPs) with numerous oxygen vacancies as a promising anode for lithium ion battery applications.
ZnO substituted with transitional metal ions at the cationic site present interesting magnetic pr... more ZnO substituted with transitional metal ions at the cationic site present interesting magnetic properties due to the strong sp-d exchange interaction which are expected to play a vital role in SPINTRONICS applications. The preparation route plays a vital role in the synthesis of single phase oxide diluted magnetic semiconductors (DMS). Zn 0.95 Ni 0.05 O prepared by both co-precipitation and ceramic methods were analyzed in detail by powder X-ray diffraction. Pelleted samples examined for their magnetic property using vibrating sample magnetometer indicated ferromagnetic-like behavior at 300 K. Comparing the results of measurements performed on both the samples, we conclude co-precipitation method to be more effective in obtaining single phase compound with desirable properties by the relatively low temperature processing of the precipitated hydroxides.
ZnO substituted with transitional metal ions at the cationic site presents interesting magnetic p... more ZnO substituted with transitional metal ions at the cationic site presents interesting magnetic properties arising due to the strong sp-d exchange interaction. They are intensively explored for spintronics applications. The preparation route plays a vital role in the synthesis of single phase oxide Diluted Magnetic Semiconductor (DMS). Single phase Zn 0.95 Mn 0.05 O prepared by co-precipitation and standard ceramic methods was confirmed by powder X-ray diffraction measurements. The sample prepared by co-precipitation method was pelleted and examined for its magnetic property using Vibrating Sample Magnetometer (VSM) indicated ferromagnetic-like behavior at 300 K. Spin-glass state was observed at 77 K. Mn substitution in ZnO affects the transparency considerably in the visible region. Comparing the results of measurements performed on samples prepared by both the methods we conclude co-precipitation method to be more effective than ceramic method in obtaining single phase compound with desirable properties. D
Studies on spray deposited transparent conducting Li doped SnO 2 thin films are scarce. Li (0 to ... more Studies on spray deposited transparent conducting Li doped SnO 2 thin films are scarce. Li (0 to 5 wt.%) doped SnO 2 thin films spray deposited onto glass substrates at 773 K in air from chloride precursors were studied for their structural, optical and temperature dependent electrical behaviors. X-ray diffraction patterns indicated single phase with polycrystalline nature. Systematic variation in surface morphology on Li doping was examined by scanning electron microscopy and atomic force microscopy. Film thickness, optical band gap (direct and indirect), sheet resistance and figure of merit were computed from spectral transmittance and temperature dependent resistivity data. Lithium doping was found to decrease the value of sheet resistance by an order in magnitude. Activation energy was computed from temperature dependent electrical resistivity data measured in the range 300 to 448 K. The 4 wt.% Li doped SnO 2 film was found to have a high value of figure of merit among other films. The results are discussed.
Nb 2 O 5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolys... more Nb 2 O 5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to be 70-80% transparent in the visible region. Direct, indirect band gap and phonon energy are also estimated. Cyclic voltammetry measurement indicate distinct anodic peak during negative potential of the scan due to Li extraction. A reversible colour change from transparent to grey has been observed. The photo-electrochemical characteristic of the dye sensitized solar cell is studied by recording the I-V characteristics of the unsealed type cell under illumination of 40 mW/cm 2 using a solar simulator.
Abstract We have deposited a large area (10 × 10 cm2) Sb-doped SnO2 (ATO) thin film transparent c... more Abstract We have deposited a large area (10 × 10 cm2) Sb-doped SnO2 (ATO) thin film transparent conducting electrode (TCE) using chemical spray pyrolysis method. The XRD analysis confirms tetragonal crystal structure of ATO thin film with significant preferred orientation. The XPS analysis clearly indicates the presence of Sb in +5 charge state when substituted into the SnO2 lattice. The UV–Vis transmittance spectra of the film showed average transmittance of 77.5% at 550 nm and the calculated direct band gap value was 3.82 eV. As-deposited ATO film exhibited lowest sheet resistivity and resistance of 6.715 × 10−4 Ω cm and 31.91 Ω/□ respectively due to Sb-dopant effect into the Sn lattice. Doping with Sb into SnO2 exhibits high carrier concentration of 7.899 × 1020 cm−3 and mobility of 28.45 cm2/Vs resulting in enhanced electrical transport properties. The variation of the sheet resistance of the large area deposited film is estimated across every 1 × 1 cm2 surface area. Variation of sheet resistance of the ATO film as a function of annealing temperature and duration was found to be appreciably stable. Kelvin probe study yielded a surface work function of 5.14 eV for the ATO film indicating the suitability to serve as an indium-free alternate TCE for optoelectronic device applications.
Journal of Atomic, Molecular, and Optical Physics, 2011
Bulk Zn0.95TM0.05O (TM=Cr, Mn, Fe, Co, and Ni) were synthesized by the standard ceramic method an... more Bulk Zn0.95TM0.05O (TM=Cr, Mn, Fe, Co, and Ni) were synthesized by the standard ceramic method and explored for variation in their band gap energies using Diffuse Reflectance Spectroscopy in the ultraviolet-visible region. Phase quantification and compositional studies were performed using Rietveld analysis of the X-Ray Diffraction patterns, Scanning Electron microscopy, and Energy Dispersive X-Ray Analysis. Due to 3d transition ion doping, the samples have brilliant colors, and the absorption edge of Zn0.95TM0.05O was found to shift towards the visible and ultraviolet-visible region. The blue and red shifts in band gaps observed for various transition metal ion-doped ZnO are discussed.
Non-local electrical properties of pulsed laser deposited La0.7Sr0.3MnO3/Bi2Sr2CaCu2O8/La0.7Sr0.3... more Non-local electrical properties of pulsed laser deposited La0.7Sr0.3MnO3/Bi2Sr2CaCu2O8/La0.7Sr0.3MnO3 (L-B-L) coplanar tri-layer is investigated under different wiring configurations. Long range super-current of Bi-2212 penetrating into LSMO is dependent on geometry of spin injection. From qualitative analysis of structural, magnetic and electrical data, long range super-current is suggested to pass through domain walls and/or grain boundaries of LSMO.
Transactions of the Indian Institute of Metals, 2011
Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis ... more Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to
ABSTRACT Undoped and lithium (Li) (1-5 wt%) doped MoO3 thin films were deposited over ITO coated ... more ABSTRACT Undoped and lithium (Li) (1-5 wt%) doped MoO3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325 °C. Undoped film was oriented along the <0 k 0> direction. The texture coefficient value of the undoped film was higher for the (0 2 0) plane compared to other planes of undoped and 'Li' doped films. The 100% peak (0 2 1) plane of orthorhombic MoO3 and hexagonal phase were induced upon doping with 'Li'. The crystallite size of the undoped film is less compared to the 'Li' doped films. The intense Raman peak at 996 cm-1 is due to the terminal oxygen (Mo6+ = O stretching mode) in the orthorhombic α-MoO3 phase. The characteristic Mo 3d5/2 and 3d3/2 doublet caused by spin-orbit coupling are clearly resolved with a splitting of 3.1 eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with 'Li' compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with 'Li' concentration. Cyclic voltammetry result shows that the presence of mixed phases in 'Li' doped films decreases the electrochemical performance. Transport study reveals that the carrier concentration and mobility of the 'Li' doped films are lower compared to the undoped film which is due to the evolution of hexagonal phase upon doping with 'Li'. A dye sensitized solar cell (DSSC) was fabricated using undoped MoO3 film as photoanode and its efficiency is calculated.
Advances in Materials Science and Engineering, 2010
Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic m... more Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, andα-Fe2O3having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM) measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature () was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also d...
ABSTRACT In this work, we report observation of two superconducting transitions and their respons... more ABSTRACT In this work, we report observation of two superconducting transitions and their response to an external field in pulsed laser deposited YBa2Cu3O7/La0.7Sr0.3MnO3/YBa2Cu3O7 (Y-L-Y) hetero-epitaxial tri-layer. Magnetization data of Y-L-Y tri-layer in “out-plane” geometry showed a single Meissner transition indicating superconductivity of the top and bottom YBa2Cu3O7 layers to be magnetically coupled. In contradiction, the magneto-transport data unusually showed two transition onsets Tcon1 and Tcon2 implying electrically decoupled superconductivity. The Tcon1 decreased systematically with field, whereas Tcon2 showed anomalous behavior with substantial increase in transition width due to the local stray field induced vortex states.
Hydrothermally synthesized mesoporous carbon coated SnO2 nanoparticles (NPs) with numerous oxygen... more Hydrothermally synthesized mesoporous carbon coated SnO2 nanoparticles (NPs) with numerous oxygen vacancies as a promising anode for lithium ion battery applications.
ZnO substituted with transitional metal ions at the cationic site present interesting magnetic pr... more ZnO substituted with transitional metal ions at the cationic site present interesting magnetic properties due to the strong sp-d exchange interaction which are expected to play a vital role in SPINTRONICS applications. The preparation route plays a vital role in the synthesis of single phase oxide diluted magnetic semiconductors (DMS). Zn 0.95 Ni 0.05 O prepared by both co-precipitation and ceramic methods were analyzed in detail by powder X-ray diffraction. Pelleted samples examined for their magnetic property using vibrating sample magnetometer indicated ferromagnetic-like behavior at 300 K. Comparing the results of measurements performed on both the samples, we conclude co-precipitation method to be more effective in obtaining single phase compound with desirable properties by the relatively low temperature processing of the precipitated hydroxides.
ZnO substituted with transitional metal ions at the cationic site presents interesting magnetic p... more ZnO substituted with transitional metal ions at the cationic site presents interesting magnetic properties arising due to the strong sp-d exchange interaction. They are intensively explored for spintronics applications. The preparation route plays a vital role in the synthesis of single phase oxide Diluted Magnetic Semiconductor (DMS). Single phase Zn 0.95 Mn 0.05 O prepared by co-precipitation and standard ceramic methods was confirmed by powder X-ray diffraction measurements. The sample prepared by co-precipitation method was pelleted and examined for its magnetic property using Vibrating Sample Magnetometer (VSM) indicated ferromagnetic-like behavior at 300 K. Spin-glass state was observed at 77 K. Mn substitution in ZnO affects the transparency considerably in the visible region. Comparing the results of measurements performed on samples prepared by both the methods we conclude co-precipitation method to be more effective than ceramic method in obtaining single phase compound with desirable properties. D
Studies on spray deposited transparent conducting Li doped SnO 2 thin films are scarce. Li (0 to ... more Studies on spray deposited transparent conducting Li doped SnO 2 thin films are scarce. Li (0 to 5 wt.%) doped SnO 2 thin films spray deposited onto glass substrates at 773 K in air from chloride precursors were studied for their structural, optical and temperature dependent electrical behaviors. X-ray diffraction patterns indicated single phase with polycrystalline nature. Systematic variation in surface morphology on Li doping was examined by scanning electron microscopy and atomic force microscopy. Film thickness, optical band gap (direct and indirect), sheet resistance and figure of merit were computed from spectral transmittance and temperature dependent resistivity data. Lithium doping was found to decrease the value of sheet resistance by an order in magnitude. Activation energy was computed from temperature dependent electrical resistivity data measured in the range 300 to 448 K. The 4 wt.% Li doped SnO 2 film was found to have a high value of figure of merit among other films. The results are discussed.
Nb 2 O 5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolys... more Nb 2 O 5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to be 70-80% transparent in the visible region. Direct, indirect band gap and phonon energy are also estimated. Cyclic voltammetry measurement indicate distinct anodic peak during negative potential of the scan due to Li extraction. A reversible colour change from transparent to grey has been observed. The photo-electrochemical characteristic of the dye sensitized solar cell is studied by recording the I-V characteristics of the unsealed type cell under illumination of 40 mW/cm 2 using a solar simulator.
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