ZnO:In thin films were deposited by chemical spray pyrolysis from zinc acetate solutions containi... more ZnO:In thin films were deposited by chemical spray pyrolysis from zinc acetate solutions containing 3 at.% of InCl 3. The films were grown in the temperature region of 400-500 °C using solution spraying rates 0.6-7.1 ml/min. ZnO:In films were characterized by XRD, Hall and van der Pauw methods. The dependence of the film resistivity vs growth temperature is parabolic. ZnO:In films with resistivity minimum of 3x10-3 Ωcm can be deposited at 450 °C. The solution spraying rate has strong effect on the film resistivity, deposition rates below 3 ml/min result in high resistivities.
Excitation power and temperature dependences of the steady-state photoluminescence (PL) spectra a... more Excitation power and temperature dependences of the steady-state photoluminescence (PL) spectra are studied in polycrystalline Cu2CdGeSe4 (CCGSe) containing a mixture of orthorhombic and tetragonal phases. The low-temperature excitation power dependences of the PL peak shape with a peak position at about 1.17 eV indicate a state filling effect. Reflectivity measurements revealed band gap energies 1.257 eV and 1.223 eV at 10 K and 300 K, respectively. The temperature dependences of the peak energy and linewidth showed a 'S-shaped' and 'V-shaped' behavior, respectively, and are well explained by the localized carriers model where band gap fluctuations play a crucial role. The asymmetric PL band shape analysis indicates the presence of hot carriers having a temperature about 75 K higher than the lattice temperature. It is shown that the low-temperature PL emission is due to recombination of localized electrons with holes captured by the deep acceptor defect CuCd with a depth E A = 80 meV.
Preparation of electrocatalysts often relies on the use of multiple starting materials-inorganic ... more Preparation of electrocatalysts often relies on the use of multiple starting materials-inorganic salts or organometallic precursors, nanostructured carbon supports, organic additives, dopants and carbonization under modifying atmospheres (e.g. NH 3 or H 2)-with the examples of electrocatalysts arising from a single precursor being much less common. Herein, we have surveyed a series of heterobivalent scaffolds to identify an iron/benzimidazole-based metal-organic framework as a uniform starting material. By merging the catechol and imidazole units together, we get direct entry into a highly efficient bifunctional oxygen electrocatalyst, which alleviates the need for additional dopants and modifying conditions (ORR: E on = 1.01 V, E 1/2 = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm-2 in 0.1 M KOH; ∆E = 0.73 V). We demonstrate that by fine-tuning the chemical nature of an organic linker, one is able modulate the electrochemical properties of a single precursor-derived electrocatalyst material. File list (2) download file view on ChemRxiv Ping et al_v2.pdf (1.09 MiB) download file view on ChemRxiv Ping_et_al_SI_v2.pdf (2.83 MiB)
Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presen... more Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.
The sol-gel spray pyrolysis method was used to grow TiO 2 thin films onto silicon wafers at subst... more The sol-gel spray pyrolysis method was used to grow TiO 2 thin films onto silicon wafers at substrate temperatures between 315 and 500-C using pulsed spray solution feed followed by annealing in the temperature interval from 500 to 800-C in air. According to FTIR, XRD, and Raman, the anatase/rutile phase transformation temperature was found to depend on the film deposition temperature. Film thickness and refractive index were determined by Ellipsometry, giving the refractive indexes of 2.1-2.3 and 2.2-2.6 for anatase and rutile, respectively. According to AFM, film roughness increases with annealing temperature from 700 to 800-C from 0.60 to 1.10 nm and from 0.35 to 0.70 nm for the films deposited at 375 and 435-C, respectively. The effective dielectric constant values were in the range of 36 to 46 for anatase and 53 to 70 for rutile at 10 kHz. The conductivity activation energy for TiO 2 films with anatase and rutile structure was found to be 100 and 60 meV, respectively.
CuInS 2 (CIS) films were prepared by chemical spray pyrolysis (CSP) method in air using CuCl 2 , ... more CuInS 2 (CIS) films were prepared by chemical spray pyrolysis (CSP) method in air using CuCl 2 , InCl 3 and SC(NH 2) 2 as precursor materials. The effect of the absorber growth temperature in the interval of 240-350 °C and precursors' molar ratio in the spray solution on the CIS film properties and ZnO/In 2 S 3 /CIS-type CSP-deposited thin film solar cell output characteristics has been studied. CIS films were characterized by XRD and EDX, solar cells were characterized by IV curves in dark and under illumination, and junction barrier height (Φ b). The highest Φ b of 1170 meV and open circuit voltage (V oc) of 560 mV were recorded for the cell with CIS absorber grown at 250 °C. Increasing the CIS deposition temperature decreases Φ b and V oc , makes a component of solar cell photosensitive and increases current density. The precursors' molar ratio in spray solution becomes relevant at CIS growth temperatures higher than 300 °C as deposition of thiourea-rich solutions suppresses oxide formation in CIS layer and contributes to higher open circuit voltage.
In this contribution we present work on rapid thermal annealing of as-electrodeposited thin films... more In this contribution we present work on rapid thermal annealing of as-electrodeposited thin films of Cu2ZnSnS4. The treatment was carried out in cold wall tubular reactor in dynamic conditions with variations of temperature, speed and time of the specific elements of the process. The effect of annealing was investigated by X-ray diffractometry, Raman scattering and Scanning Electron Microscopy (SEM). The phase composition of the films in dependence on conditions of treatment was analysed and have been shown that in slow and prolonged high-temperature process the low temperature binaries react completely and only Kesterite and ZnS is left. In addition, structural investigations by XRD have shown gradual decrease of crystallite sizes when the temperature level and duration of the high-temperature segment increases and respectively increase in the strain, due to formation of the phases in non-equilibrium conditions. In opposite, when the speed of dynamic segments in the process decreas...
The deposition of nickel oxide (NiOx) thin film from an acetylacetonate source using many solutio... more The deposition of nickel oxide (NiOx) thin film from an acetylacetonate source using many solution-based techniques has been avoided owing to its poor solubility in alcohol solvents. From this perspective, this work provides a systematic investigation of the development of NiOx thin film, using a combinative approach of ultrasonic spray pyrolysis (USP) and Li dopant for the synthesis and optimization of structural and optoelectronic properties of the films. An in-depth comparative analysis of nickel acetylacetonate-based precursor, employing acetonitrile and methanol as solvents, is provided. It is demonstrated that USP from acetylacetonate precursor yielded uniform, well-compact, and transparent films, with polycrystalline cubic NiOx crystal structures. By screening the deposition temperature in the range of 300–450°C, a temperature of 400°C was identified as an optimal processing temperature leading to uniform, compact, highly transparent, and p-type conductive films. At optimized...
Enhanced photocatalytic oxidation of indoor VOC mixtures on transparent polycrystalline spray-dep... more Enhanced photocatalytic oxidation of indoor VOC mixtures on transparent polycrystalline spray-deposited TiO2 thin films under ultraviolet and visible light.
We describe a unique amorphous cobalt metal–organic framework derived material that acts both as ... more We describe a unique amorphous cobalt metal–organic framework derived material that acts both as a recyclable heterogeneous catalyst for organic transformations and as a trifunctional electrocatalyst.
doped TiO2 thin film by spray pyrolysis, characterization of the film, analysis of results, and m... more doped TiO2 thin film by spray pyrolysis, characterization of the film, analysis of results, and major role in writing. II Deposition of ZrOx thin film by spray pyrolysis, characterization of the thin film, analysis of results, and major role in writing. III Deposition of ZrOx thin film by spray; deposition of the ZTO layer by spin coating, characterization of the layers, fabrication device, characterization of TFTs, analysis of results, and major role in writing. IV Deposition of ZrOx thin film by spray, UV-Ozone surface treatment, thin film characterizations, fabrication of TFT, analysis of the device, and major role in writing. LED
Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor e... more Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor elemental powders, followed by in-situ synthesis of tungsten carbide. This approach promotes formation of ultrafine microstructure favored in many cemented carbide applications. Our study focuses on the effect of mechanical activation (high-energy milling) on the properties of powder and following thermal activation (sintering) on the microstructure characteristics and phase composition. Reactive sintering proved effective – an ultrafine grained microstructure of cemented carbides with Co and Fe binders was achieved. Formation of tungsten carbide grains was complete at low temperature during reactive spark plasma sintering, resulting in textured microstructure with anisotropic grain formation and growth.
The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduc... more The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduce or even avoid the usage of conventional binder metals – nickel and cobalt. Commonly, austenitic Fe-Ni alloys have been preferred choice for substituting Co. Similar to Ni, manganese acts as austenite stabilizer and studies have shown that Fe-Mn alloys offer alternative binder metal to Co and Ni in cemented tungsten carbides. In addition, Fe-Mn as a binder potentially offers improved wear resistance due to the well-known wear properties of Fe-Mn-C steels. Addition of chromium to the binder composition increases corrosion performance of composite. Cemented carbides bonded with austenitic FeCrNi binder have demonstrated promising performance. In present work the possibility of achieving austenitic binder phase through substitution of nickel by manganese as an austenite stabilizer is investigated. Structure formation, phase composition and mechanical performance of WC-FeMn and WC-FeCrMn ce...
ZnO:In thin films were deposited by chemical spray pyrolysis from zinc acetate solutions containi... more ZnO:In thin films were deposited by chemical spray pyrolysis from zinc acetate solutions containing 3 at.% of InCl 3. The films were grown in the temperature region of 400-500 °C using solution spraying rates 0.6-7.1 ml/min. ZnO:In films were characterized by XRD, Hall and van der Pauw methods. The dependence of the film resistivity vs growth temperature is parabolic. ZnO:In films with resistivity minimum of 3x10-3 Ωcm can be deposited at 450 °C. The solution spraying rate has strong effect on the film resistivity, deposition rates below 3 ml/min result in high resistivities.
Excitation power and temperature dependences of the steady-state photoluminescence (PL) spectra a... more Excitation power and temperature dependences of the steady-state photoluminescence (PL) spectra are studied in polycrystalline Cu2CdGeSe4 (CCGSe) containing a mixture of orthorhombic and tetragonal phases. The low-temperature excitation power dependences of the PL peak shape with a peak position at about 1.17 eV indicate a state filling effect. Reflectivity measurements revealed band gap energies 1.257 eV and 1.223 eV at 10 K and 300 K, respectively. The temperature dependences of the peak energy and linewidth showed a 'S-shaped' and 'V-shaped' behavior, respectively, and are well explained by the localized carriers model where band gap fluctuations play a crucial role. The asymmetric PL band shape analysis indicates the presence of hot carriers having a temperature about 75 K higher than the lattice temperature. It is shown that the low-temperature PL emission is due to recombination of localized electrons with holes captured by the deep acceptor defect CuCd with a depth E A = 80 meV.
Preparation of electrocatalysts often relies on the use of multiple starting materials-inorganic ... more Preparation of electrocatalysts often relies on the use of multiple starting materials-inorganic salts or organometallic precursors, nanostructured carbon supports, organic additives, dopants and carbonization under modifying atmospheres (e.g. NH 3 or H 2)-with the examples of electrocatalysts arising from a single precursor being much less common. Herein, we have surveyed a series of heterobivalent scaffolds to identify an iron/benzimidazole-based metal-organic framework as a uniform starting material. By merging the catechol and imidazole units together, we get direct entry into a highly efficient bifunctional oxygen electrocatalyst, which alleviates the need for additional dopants and modifying conditions (ORR: E on = 1.01 V, E 1/2 = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm-2 in 0.1 M KOH; ∆E = 0.73 V). We demonstrate that by fine-tuning the chemical nature of an organic linker, one is able modulate the electrochemical properties of a single precursor-derived electrocatalyst material. File list (2) download file view on ChemRxiv Ping et al_v2.pdf (1.09 MiB) download file view on ChemRxiv Ping_et_al_SI_v2.pdf (2.83 MiB)
Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presen... more Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.
The sol-gel spray pyrolysis method was used to grow TiO 2 thin films onto silicon wafers at subst... more The sol-gel spray pyrolysis method was used to grow TiO 2 thin films onto silicon wafers at substrate temperatures between 315 and 500-C using pulsed spray solution feed followed by annealing in the temperature interval from 500 to 800-C in air. According to FTIR, XRD, and Raman, the anatase/rutile phase transformation temperature was found to depend on the film deposition temperature. Film thickness and refractive index were determined by Ellipsometry, giving the refractive indexes of 2.1-2.3 and 2.2-2.6 for anatase and rutile, respectively. According to AFM, film roughness increases with annealing temperature from 700 to 800-C from 0.60 to 1.10 nm and from 0.35 to 0.70 nm for the films deposited at 375 and 435-C, respectively. The effective dielectric constant values were in the range of 36 to 46 for anatase and 53 to 70 for rutile at 10 kHz. The conductivity activation energy for TiO 2 films with anatase and rutile structure was found to be 100 and 60 meV, respectively.
CuInS 2 (CIS) films were prepared by chemical spray pyrolysis (CSP) method in air using CuCl 2 , ... more CuInS 2 (CIS) films were prepared by chemical spray pyrolysis (CSP) method in air using CuCl 2 , InCl 3 and SC(NH 2) 2 as precursor materials. The effect of the absorber growth temperature in the interval of 240-350 °C and precursors' molar ratio in the spray solution on the CIS film properties and ZnO/In 2 S 3 /CIS-type CSP-deposited thin film solar cell output characteristics has been studied. CIS films were characterized by XRD and EDX, solar cells were characterized by IV curves in dark and under illumination, and junction barrier height (Φ b). The highest Φ b of 1170 meV and open circuit voltage (V oc) of 560 mV were recorded for the cell with CIS absorber grown at 250 °C. Increasing the CIS deposition temperature decreases Φ b and V oc , makes a component of solar cell photosensitive and increases current density. The precursors' molar ratio in spray solution becomes relevant at CIS growth temperatures higher than 300 °C as deposition of thiourea-rich solutions suppresses oxide formation in CIS layer and contributes to higher open circuit voltage.
In this contribution we present work on rapid thermal annealing of as-electrodeposited thin films... more In this contribution we present work on rapid thermal annealing of as-electrodeposited thin films of Cu2ZnSnS4. The treatment was carried out in cold wall tubular reactor in dynamic conditions with variations of temperature, speed and time of the specific elements of the process. The effect of annealing was investigated by X-ray diffractometry, Raman scattering and Scanning Electron Microscopy (SEM). The phase composition of the films in dependence on conditions of treatment was analysed and have been shown that in slow and prolonged high-temperature process the low temperature binaries react completely and only Kesterite and ZnS is left. In addition, structural investigations by XRD have shown gradual decrease of crystallite sizes when the temperature level and duration of the high-temperature segment increases and respectively increase in the strain, due to formation of the phases in non-equilibrium conditions. In opposite, when the speed of dynamic segments in the process decreas...
The deposition of nickel oxide (NiOx) thin film from an acetylacetonate source using many solutio... more The deposition of nickel oxide (NiOx) thin film from an acetylacetonate source using many solution-based techniques has been avoided owing to its poor solubility in alcohol solvents. From this perspective, this work provides a systematic investigation of the development of NiOx thin film, using a combinative approach of ultrasonic spray pyrolysis (USP) and Li dopant for the synthesis and optimization of structural and optoelectronic properties of the films. An in-depth comparative analysis of nickel acetylacetonate-based precursor, employing acetonitrile and methanol as solvents, is provided. It is demonstrated that USP from acetylacetonate precursor yielded uniform, well-compact, and transparent films, with polycrystalline cubic NiOx crystal structures. By screening the deposition temperature in the range of 300–450°C, a temperature of 400°C was identified as an optimal processing temperature leading to uniform, compact, highly transparent, and p-type conductive films. At optimized...
Enhanced photocatalytic oxidation of indoor VOC mixtures on transparent polycrystalline spray-dep... more Enhanced photocatalytic oxidation of indoor VOC mixtures on transparent polycrystalline spray-deposited TiO2 thin films under ultraviolet and visible light.
We describe a unique amorphous cobalt metal–organic framework derived material that acts both as ... more We describe a unique amorphous cobalt metal–organic framework derived material that acts both as a recyclable heterogeneous catalyst for organic transformations and as a trifunctional electrocatalyst.
doped TiO2 thin film by spray pyrolysis, characterization of the film, analysis of results, and m... more doped TiO2 thin film by spray pyrolysis, characterization of the film, analysis of results, and major role in writing. II Deposition of ZrOx thin film by spray pyrolysis, characterization of the thin film, analysis of results, and major role in writing. III Deposition of ZrOx thin film by spray; deposition of the ZTO layer by spin coating, characterization of the layers, fabrication device, characterization of TFTs, analysis of results, and major role in writing. IV Deposition of ZrOx thin film by spray, UV-Ozone surface treatment, thin film characterizations, fabrication of TFT, analysis of the device, and major role in writing. LED
Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor e... more Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor elemental powders, followed by in-situ synthesis of tungsten carbide. This approach promotes formation of ultrafine microstructure favored in many cemented carbide applications. Our study focuses on the effect of mechanical activation (high-energy milling) on the properties of powder and following thermal activation (sintering) on the microstructure characteristics and phase composition. Reactive sintering proved effective – an ultrafine grained microstructure of cemented carbides with Co and Fe binders was achieved. Formation of tungsten carbide grains was complete at low temperature during reactive spark plasma sintering, resulting in textured microstructure with anisotropic grain formation and growth.
The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduc... more The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduce or even avoid the usage of conventional binder metals – nickel and cobalt. Commonly, austenitic Fe-Ni alloys have been preferred choice for substituting Co. Similar to Ni, manganese acts as austenite stabilizer and studies have shown that Fe-Mn alloys offer alternative binder metal to Co and Ni in cemented tungsten carbides. In addition, Fe-Mn as a binder potentially offers improved wear resistance due to the well-known wear properties of Fe-Mn-C steels. Addition of chromium to the binder composition increases corrosion performance of composite. Cemented carbides bonded with austenitic FeCrNi binder have demonstrated promising performance. In present work the possibility of achieving austenitic binder phase through substitution of nickel by manganese as an austenite stabilizer is investigated. Structure formation, phase composition and mechanical performance of WC-FeMn and WC-FeCrMn ce...
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