Umapada Pal - Academia.edu (original) (raw)

Papers by Umapada Pal

Research paper thumbnail of Indium doping induced defect structure evolution and photocatalytic activity of hydrothermally grown small SnO 2 nanoparticles

Well-crystalline SnO2 nanoparticles of 4-5 nm size with different In contents were synthesized by... more Well-crystalline SnO2 nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in SnO2 lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of SnO2 lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of SnO2 nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of SnO2 crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped SnO2 nanoparticles occurs through the production of intermediate byproduc...

Research paper thumbnail of Evaluation of thermally and chemically reduced graphene oxide films as counter electrodes on dye-sensitized solar cells

Graphene oxide (GO) was prepared by modified Hummer's method to produce reduced graphene oxid... more Graphene oxide (GO) was prepared by modified Hummer's method to produce reduced graphene oxide (RGO) following standard thermal and chemical reduction processes. Prepared RGO colloids were utilized to fabricate RGO films over glass and FTO coated glass substrates through drop-coating. A systematic study was performed to evaluate the effect of reduction degree on the optical and electrical properties of the RGO film. We demonstrate that both the reduction process (thermal and chemical) produce RGO films of similar optical and electrical behaviors. However, the RGO films fabricated using chemically reduced GO colloid render better performance in dye sensitized solar cells (DSSCs), when they are used as counter electrodes (CEs). It has been demonstrated that RGO films of optimum thicknesses fabricated using RGO colloids prepared using lower concentration of hydrazine reducer have better catalytic performance in DSSCs due to a better catalytic interaction with redox couple. The bett...

Research paper thumbnail of Performance of asymmetric supercapacitor fabricated with perovskite‐type Sr 2+ ‐incorporated LaMnO 3 (La 0. 7 Sr 0 . 3 MnO 3 ) nanostructures in neutral 1M Na 2 SO 4 aqueous electrolyte

International Journal of Energy Research, 2021

Research paper thumbnail of Waveguiding behavior of VLS-grown one-dimensional Ga-doped In 2 O 3 nanostructures

Current Applied Physics, 2018

Highly crystalline undoped and Ga-doped indium oxide nanorods with square-shaped faceted morpholo... more Highly crystalline undoped and Ga-doped indium oxide nanorods with square-shaped faceted morphology were fabricated through the vapor-liquid-solid process at moderate temperature. Effects of Ga incorporation on the growth rate, morphology, and crystallinity of the nanostructures were evaluated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Defect structure and waveguiding behavior of the 1-D In 2 O 3 nanostructures have been studied using microRaman and micro photoluminescence spectroscopies. The appearance of several resonant modes superposed over the broad room temperature micro-photoluminescence spectra of the nanostructures demonstrates their waveguiding behaviors. While the pristine or undoped In 2 O 3 nanostructures of 20-150 nm widths revealed Fabry-Pérot resonance modes, the Ga-incorporated nanostructures of 20-100 nm width revealed whispering gallery modes due to their smaller widths. The quality factor (Q) of the resonators was estimated to be about 20.86 and 188.79 for the pristine and Ga-incorporated nanostructures, respectively, indicating a huge enhancement due to Ga incorporation. The increment in the Q factor on Ga incorporation in In 2 O 3 nanorods opens up the possibility of their utilization for the development of new optical transmitters and resonators, and fabrication of nanoscopic lasing devices.

Research paper thumbnail of Borohydride-Assisted Surface Activation of Co3O4/CoFe2O4 Composite and Its Catalytic Activity for 4-Nitrophenol Reduction

ACS Omega, 2019

Surface activation of catalysts is known to be an efficient process to enhance their activity in ... more Surface activation of catalysts is known to be an efficient process to enhance their activity in catalytic processes. The activation process includes the generation of oxygen vacancies, changing the nature of the catalyst surface from acidic to basic and vice versa, and the reduction of catalyst surface by H 2. On the other hand, magnetically separable catalysts are highly beneficial for their utilization in water or biological fluid-based catalytic processes, as they can be easily guided to the target site and recovered. Here, we present the fabrication of CoFe 2 O 4 and composites of Co 3 O 4 / CoFe 2 O 4 /α-Fe 2 O 3 and Co/CoFe 2 O 4 /α-Fe 2 O 3 through solution combustion process to utilize them as catalysts for 4-nitrophenol (4-NP) reduction. Although none of the asprepared CoFe 2 O 4 and Co 3 O 4 /CoFe 2 O 4 was seen to be active in 4-NP reduction reaction, the surface of the composite gets activated by borohydride (NaBH 4) treatment to act as a highly active catalyst for 4-NP reduction. X-ray photoelectron spectroscopy of the composite revealed the formation of metal-hydroxide (M−O−H) species of both Co and Fe at its surface due to borohydride treatment. The mechanism of the surface activation and the dynamics of 4-NP reduction of the surfaceactivated composite have been studied, proposing a possible pathway for the reduction of 4-NP.

Research paper thumbnail of Structural, Magnetic, and Catalytic Evaluation of Spinel Co, Ni, and Co–Ni Ferrite Nanoparticles Fabricated by Low-Temperature Solution Combustion Process

ACS Omega, 2018

Here, we present the low-temperature (∼600°C) solution combustion method for the fabrication of C... more Here, we present the low-temperature (∼600°C) solution combustion method for the fabrication of CoFe 2 O 4 , NiFe 2 O 4 , and Co 0.5 Ni 0.5 Fe 2 O 4 nanoparticles (NPs) of 12−64 nm range in pure cubic spinel structure, by adjusting the oxidant (nitrate ions)/reductant (glycine) ratio in the reaction mixture. Although nitrate ions/glycine (N/G) ratios of 3 and 6 were used for the synthesis, phase-pure NPs could be obtained only for the N/G ratio of 6. For the N/G ratio 3, certain amount of Ni 2+ cations was reduced to metallic nickel. The NH 3 gas generated during the thermal decomposition of the amino acid (glycine, H 2 NCH 2 COOH) induced the reduction reaction. X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy techniques were utilized to characterize the synthesized materials. XRD analyses of the samples indicate that the Co 0.5 Ni 0.5 Fe 2 O 4 NPs have lattice parameter larger than that of NiFe 2 O 4 , but smaller than that of CoFe 2 O 4 NPs. Although the saturation magnetization (M s) of Co 0.5 Ni 0.5 Fe 2 O 4 NPs lies in between the saturation magnetization values of CoFe 2 O 4 and NiFe 2 O 4 NPs, high coercivity (H c , 875 Oe) of the NPs indicate their hard ferromagnetic behavior. Catalytic behavior of the fabricated spinel NPs revealed that the samples containing metallic Ni are active catalysts for the degradation of 4-nitrophenol in aqueous medium.

Research paper thumbnail of Fabrication of Monodispersed Au@SiO2 Nanoparticles with Highly Stable Silica Layers by Ultrasound-Assisted Stöber Method

The Journal of Physical Chemistry C, 2017

Research paper thumbnail of Au 0 –Au 3+ bifunctional site mediated enhanced catalytic activity of Au/ZnO composite in diesel particulate matter oxidation

Journal of Catalysis, 2017

Hydrogen-reduced air-calcined 1%Au/ZnO composite synthesized by gold impregnation in ZnO has been... more Hydrogen-reduced air-calcined 1%Au/ZnO composite synthesized by gold impregnation in ZnO has been utilized as catalyst for diesel particulate matter (DPM) oxidation. The catalyst was characterized by UVvis optical absorption, X-ray photoelectron spectroscopy and transmission electronic microscopy. The composite catalyst showed excellent activity for the oxidation of DPM at temperature as low as 230°C. The activity of the catalyst does not change up to 6 oxidation cycles. The high catalytic activity of the composite has been attributed to the formation of stable Au 0-Au 3+ bifunctional catalytic sites at the gold-ZnO interface, which enhances the contact efficiency of solid particulate matter on Au 3+ and the generation of superoxide species on Au 0. The high stability of the bifunctional Au 0-Au 3+ sites is associated with the electronic interactions between gold and n-type semiconductor ZnO at their interface.

Research paper thumbnail of Electronic state of silver in Ag/SiO 2 and Ag/ZnO catalysts and its effect on diesel particulate matter oxidation: An XPS study

Applied Catalysis B: Environmental, 2017

Research paper thumbnail of Low temperature wet-chemical synthesis of spherical hydroxyapatite nanoparticles and their in situ cytotoxicity study

Advances in nano research, 2016

Research paper thumbnail of Structure and optical properties of vapor grown In<sub>2</sub>O<sub>3</sub>: Ga nano-/microcrystals

Advances in nano research, 2015

Research paper thumbnail of Large Scale Synthesis of ZnO Nanostructures of Different Morphologies through Solvent-free Mechanochemical Synthesis and their Application in Photocatalytic Dye Degradation

American Journal of Engineering and Applied Sciences, 2016

Research paper thumbnail of Mixed titanium, silicon, and aluminum oxide nanostructures as novel adsorbent for removal of rhodamine 6G and methylene blue as cationic dyes from aqueous solution

Chemosphere, Jan 13, 2016

Mixed oxide nanoparticles containing Ti, Si, and Al of 8-15 nm size range were synthesized using ... more Mixed oxide nanoparticles containing Ti, Si, and Al of 8-15 nm size range were synthesized using a combined sol-gel - hydrothermal method. Effects of composition on the structure, morphology, and optical properties of the nanoparticles were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microRaman spectroscopy, and diffuse reflectance spectroscopy (DRS). Dye removal abilities of the nanoparticles from aqueous solutions were tested for different cationic dyes. While all the mixed oxide nanoparticles revealed high and fast adsorption of cationic dyes, the particles containing Ti and Si turned out to be the best. The adsorption kinetics and equilibrium adsorption behavior of the adsorbate - adsorbent systems could be well described by pseudo-second-order kinetics and Langmuir isotherm model, respectively. Estimated thermodynamic parameters revealed the adsorption process is spontaneous, driven mainly by the electrostat...

Research paper thumbnail of Optimizing the electric field around solid and core-shell alloy nanostructures for near-field applications

Nanoscale, 2016

Understanding the variations of the near electric field around plasmonic nanoparticles is very im... more Understanding the variations of the near electric field around plasmonic nanoparticles is very important for several applications where the interactions occur close to the surface of the nanoparticle.

Research paper thumbnail of Influence of morphology on the performance of ZnO-based dye-sensitized solar cells

RSC Adv., 2016

The relation between the morphological and textural properties and the performance of ZnO-based d... more The relation between the morphological and textural properties and the performance of ZnO-based dye-sensitized solar cells is explored using ZnO materials prepared by a sonochemical method as a function of pH.

Research paper thumbnail of Morphology and defect evolution in vapor-grown In2O3:Sn micro-/nanoparticles

Materials Science in Semiconductor Processing, 2015

Research paper thumbnail of Photoluminesence and FTIR study of ZnO nanoparticles: the impurity and defect perspective

physica status solidi (c), 2006

Research paper thumbnail of PREPARATION AND CHARACTERIZATION OF Cu/ZnO NANOCOMPOSITES

Modern Physics Letters B, 2001

The Cu/ZnO composite films of different Cu contents were prepared on quartz substrates by r.f. co... more The Cu/ZnO composite films of different Cu contents were prepared on quartz substrates by r.f. co-sputtering technique. The as-grown films were annealed at different temperatures in argon atmosphere to study the effect of annealing on the growth of particles. TEM images revaled the formation of nanometric particles in the matrix. For the films prepared with lower Cu contents, the size of the particles did not increase significantly on annealing them up to 400°C. Whereas, for the films grown with higher Cu contents, the cluster size increased with the increase of amlealing temperature. Optical absorption spectra of the films revealed a peak at about 560 nm correspond to the plasmon resonance absorption in small Cu particles. XRD and TED patterns revealed that the copper in the composites remain in partially oxidized state.

Research paper thumbnail of The anomalous photovoltaic effect in polycrystalline zinc telluride films

Journal of Applied Physics, 1991

Research paper thumbnail of New conducting polymers, 3. Doping, stability, electrical, and optical characteristics of poly-(P-phenylphosphoethynediyl)

Colloid & Polymer Science, 1991

Research paper thumbnail of Indium doping induced defect structure evolution and photocatalytic activity of hydrothermally grown small SnO 2 nanoparticles

Well-crystalline SnO2 nanoparticles of 4-5 nm size with different In contents were synthesized by... more Well-crystalline SnO2 nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in SnO2 lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of SnO2 lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of SnO2 nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of SnO2 crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped SnO2 nanoparticles occurs through the production of intermediate byproduc...

Research paper thumbnail of Evaluation of thermally and chemically reduced graphene oxide films as counter electrodes on dye-sensitized solar cells

Graphene oxide (GO) was prepared by modified Hummer's method to produce reduced graphene oxid... more Graphene oxide (GO) was prepared by modified Hummer's method to produce reduced graphene oxide (RGO) following standard thermal and chemical reduction processes. Prepared RGO colloids were utilized to fabricate RGO films over glass and FTO coated glass substrates through drop-coating. A systematic study was performed to evaluate the effect of reduction degree on the optical and electrical properties of the RGO film. We demonstrate that both the reduction process (thermal and chemical) produce RGO films of similar optical and electrical behaviors. However, the RGO films fabricated using chemically reduced GO colloid render better performance in dye sensitized solar cells (DSSCs), when they are used as counter electrodes (CEs). It has been demonstrated that RGO films of optimum thicknesses fabricated using RGO colloids prepared using lower concentration of hydrazine reducer have better catalytic performance in DSSCs due to a better catalytic interaction with redox couple. The bett...

Research paper thumbnail of Performance of asymmetric supercapacitor fabricated with perovskite‐type Sr 2+ ‐incorporated LaMnO 3 (La 0. 7 Sr 0 . 3 MnO 3 ) nanostructures in neutral 1M Na 2 SO 4 aqueous electrolyte

International Journal of Energy Research, 2021

Research paper thumbnail of Waveguiding behavior of VLS-grown one-dimensional Ga-doped In 2 O 3 nanostructures

Current Applied Physics, 2018

Highly crystalline undoped and Ga-doped indium oxide nanorods with square-shaped faceted morpholo... more Highly crystalline undoped and Ga-doped indium oxide nanorods with square-shaped faceted morphology were fabricated through the vapor-liquid-solid process at moderate temperature. Effects of Ga incorporation on the growth rate, morphology, and crystallinity of the nanostructures were evaluated by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Defect structure and waveguiding behavior of the 1-D In 2 O 3 nanostructures have been studied using microRaman and micro photoluminescence spectroscopies. The appearance of several resonant modes superposed over the broad room temperature micro-photoluminescence spectra of the nanostructures demonstrates their waveguiding behaviors. While the pristine or undoped In 2 O 3 nanostructures of 20-150 nm widths revealed Fabry-Pérot resonance modes, the Ga-incorporated nanostructures of 20-100 nm width revealed whispering gallery modes due to their smaller widths. The quality factor (Q) of the resonators was estimated to be about 20.86 and 188.79 for the pristine and Ga-incorporated nanostructures, respectively, indicating a huge enhancement due to Ga incorporation. The increment in the Q factor on Ga incorporation in In 2 O 3 nanorods opens up the possibility of their utilization for the development of new optical transmitters and resonators, and fabrication of nanoscopic lasing devices.

Research paper thumbnail of Borohydride-Assisted Surface Activation of Co3O4/CoFe2O4 Composite and Its Catalytic Activity for 4-Nitrophenol Reduction

ACS Omega, 2019

Surface activation of catalysts is known to be an efficient process to enhance their activity in ... more Surface activation of catalysts is known to be an efficient process to enhance their activity in catalytic processes. The activation process includes the generation of oxygen vacancies, changing the nature of the catalyst surface from acidic to basic and vice versa, and the reduction of catalyst surface by H 2. On the other hand, magnetically separable catalysts are highly beneficial for their utilization in water or biological fluid-based catalytic processes, as they can be easily guided to the target site and recovered. Here, we present the fabrication of CoFe 2 O 4 and composites of Co 3 O 4 / CoFe 2 O 4 /α-Fe 2 O 3 and Co/CoFe 2 O 4 /α-Fe 2 O 3 through solution combustion process to utilize them as catalysts for 4-nitrophenol (4-NP) reduction. Although none of the asprepared CoFe 2 O 4 and Co 3 O 4 /CoFe 2 O 4 was seen to be active in 4-NP reduction reaction, the surface of the composite gets activated by borohydride (NaBH 4) treatment to act as a highly active catalyst for 4-NP reduction. X-ray photoelectron spectroscopy of the composite revealed the formation of metal-hydroxide (M−O−H) species of both Co and Fe at its surface due to borohydride treatment. The mechanism of the surface activation and the dynamics of 4-NP reduction of the surfaceactivated composite have been studied, proposing a possible pathway for the reduction of 4-NP.

Research paper thumbnail of Structural, Magnetic, and Catalytic Evaluation of Spinel Co, Ni, and Co–Ni Ferrite Nanoparticles Fabricated by Low-Temperature Solution Combustion Process

ACS Omega, 2018

Here, we present the low-temperature (∼600°C) solution combustion method for the fabrication of C... more Here, we present the low-temperature (∼600°C) solution combustion method for the fabrication of CoFe 2 O 4 , NiFe 2 O 4 , and Co 0.5 Ni 0.5 Fe 2 O 4 nanoparticles (NPs) of 12−64 nm range in pure cubic spinel structure, by adjusting the oxidant (nitrate ions)/reductant (glycine) ratio in the reaction mixture. Although nitrate ions/glycine (N/G) ratios of 3 and 6 were used for the synthesis, phase-pure NPs could be obtained only for the N/G ratio of 6. For the N/G ratio 3, certain amount of Ni 2+ cations was reduced to metallic nickel. The NH 3 gas generated during the thermal decomposition of the amino acid (glycine, H 2 NCH 2 COOH) induced the reduction reaction. X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometry, and X-ray photoelectron spectroscopy techniques were utilized to characterize the synthesized materials. XRD analyses of the samples indicate that the Co 0.5 Ni 0.5 Fe 2 O 4 NPs have lattice parameter larger than that of NiFe 2 O 4 , but smaller than that of CoFe 2 O 4 NPs. Although the saturation magnetization (M s) of Co 0.5 Ni 0.5 Fe 2 O 4 NPs lies in between the saturation magnetization values of CoFe 2 O 4 and NiFe 2 O 4 NPs, high coercivity (H c , 875 Oe) of the NPs indicate their hard ferromagnetic behavior. Catalytic behavior of the fabricated spinel NPs revealed that the samples containing metallic Ni are active catalysts for the degradation of 4-nitrophenol in aqueous medium.

Research paper thumbnail of Fabrication of Monodispersed Au@SiO2 Nanoparticles with Highly Stable Silica Layers by Ultrasound-Assisted Stöber Method

The Journal of Physical Chemistry C, 2017

Research paper thumbnail of Au 0 –Au 3+ bifunctional site mediated enhanced catalytic activity of Au/ZnO composite in diesel particulate matter oxidation

Journal of Catalysis, 2017

Hydrogen-reduced air-calcined 1%Au/ZnO composite synthesized by gold impregnation in ZnO has been... more Hydrogen-reduced air-calcined 1%Au/ZnO composite synthesized by gold impregnation in ZnO has been utilized as catalyst for diesel particulate matter (DPM) oxidation. The catalyst was characterized by UVvis optical absorption, X-ray photoelectron spectroscopy and transmission electronic microscopy. The composite catalyst showed excellent activity for the oxidation of DPM at temperature as low as 230°C. The activity of the catalyst does not change up to 6 oxidation cycles. The high catalytic activity of the composite has been attributed to the formation of stable Au 0-Au 3+ bifunctional catalytic sites at the gold-ZnO interface, which enhances the contact efficiency of solid particulate matter on Au 3+ and the generation of superoxide species on Au 0. The high stability of the bifunctional Au 0-Au 3+ sites is associated with the electronic interactions between gold and n-type semiconductor ZnO at their interface.

Research paper thumbnail of Electronic state of silver in Ag/SiO 2 and Ag/ZnO catalysts and its effect on diesel particulate matter oxidation: An XPS study

Applied Catalysis B: Environmental, 2017

Research paper thumbnail of Low temperature wet-chemical synthesis of spherical hydroxyapatite nanoparticles and their in situ cytotoxicity study

Advances in nano research, 2016

Research paper thumbnail of Structure and optical properties of vapor grown In<sub>2</sub>O<sub>3</sub>: Ga nano-/microcrystals

Advances in nano research, 2015

Research paper thumbnail of Large Scale Synthesis of ZnO Nanostructures of Different Morphologies through Solvent-free Mechanochemical Synthesis and their Application in Photocatalytic Dye Degradation

American Journal of Engineering and Applied Sciences, 2016

Research paper thumbnail of Mixed titanium, silicon, and aluminum oxide nanostructures as novel adsorbent for removal of rhodamine 6G and methylene blue as cationic dyes from aqueous solution

Chemosphere, Jan 13, 2016

Mixed oxide nanoparticles containing Ti, Si, and Al of 8-15 nm size range were synthesized using ... more Mixed oxide nanoparticles containing Ti, Si, and Al of 8-15 nm size range were synthesized using a combined sol-gel - hydrothermal method. Effects of composition on the structure, morphology, and optical properties of the nanoparticles were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microRaman spectroscopy, and diffuse reflectance spectroscopy (DRS). Dye removal abilities of the nanoparticles from aqueous solutions were tested for different cationic dyes. While all the mixed oxide nanoparticles revealed high and fast adsorption of cationic dyes, the particles containing Ti and Si turned out to be the best. The adsorption kinetics and equilibrium adsorption behavior of the adsorbate - adsorbent systems could be well described by pseudo-second-order kinetics and Langmuir isotherm model, respectively. Estimated thermodynamic parameters revealed the adsorption process is spontaneous, driven mainly by the electrostat...

Research paper thumbnail of Optimizing the electric field around solid and core-shell alloy nanostructures for near-field applications

Nanoscale, 2016

Understanding the variations of the near electric field around plasmonic nanoparticles is very im... more Understanding the variations of the near electric field around plasmonic nanoparticles is very important for several applications where the interactions occur close to the surface of the nanoparticle.

Research paper thumbnail of Influence of morphology on the performance of ZnO-based dye-sensitized solar cells

RSC Adv., 2016

The relation between the morphological and textural properties and the performance of ZnO-based d... more The relation between the morphological and textural properties and the performance of ZnO-based dye-sensitized solar cells is explored using ZnO materials prepared by a sonochemical method as a function of pH.

Research paper thumbnail of Morphology and defect evolution in vapor-grown In2O3:Sn micro-/nanoparticles

Materials Science in Semiconductor Processing, 2015

Research paper thumbnail of Photoluminesence and FTIR study of ZnO nanoparticles: the impurity and defect perspective

physica status solidi (c), 2006

Research paper thumbnail of PREPARATION AND CHARACTERIZATION OF Cu/ZnO NANOCOMPOSITES

Modern Physics Letters B, 2001

The Cu/ZnO composite films of different Cu contents were prepared on quartz substrates by r.f. co... more The Cu/ZnO composite films of different Cu contents were prepared on quartz substrates by r.f. co-sputtering technique. The as-grown films were annealed at different temperatures in argon atmosphere to study the effect of annealing on the growth of particles. TEM images revaled the formation of nanometric particles in the matrix. For the films prepared with lower Cu contents, the size of the particles did not increase significantly on annealing them up to 400°C. Whereas, for the films grown with higher Cu contents, the cluster size increased with the increase of amlealing temperature. Optical absorption spectra of the films revealed a peak at about 560 nm correspond to the plasmon resonance absorption in small Cu particles. XRD and TED patterns revealed that the copper in the composites remain in partially oxidized state.

Research paper thumbnail of The anomalous photovoltaic effect in polycrystalline zinc telluride films

Journal of Applied Physics, 1991

Research paper thumbnail of New conducting polymers, 3. Doping, stability, electrical, and optical characteristics of poly-(P-phenylphosphoethynediyl)

Colloid & Polymer Science, 1991