This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin f... more This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin films. Uniform TiO 2 and Nb 2 O 5 composites thin films were deposited on FTO coated glass substrate using electrophoretic deposition (EPD) technique. The EPD voltage of 35V (DC) and deposition time of 90s, were used for various volume fractions of Nb 2 O 5 in composites. Uniform and crack free composite films were successfully deposited using the EPD technique as shown by the SEM micrographs. The Hall Effect equipment was used to characterize the films through measurement of current and the Hall voltage. Current against Hall voltage plot for films of various volume fractions of Nb 2 O 5 were used to determine Hall coefficients and majority charge carrier density. The sign of Hall coefficient values revealed that TiO 2 /Nb 2 O 5 composite thin films had a net n-type polarity indicating electrons were the majority charge carrier in the composite films. The results showed that dye-sensitize...
International Journal of Materials Science and Applications, 2014
Pd-F:SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precurso... more Pd-F:SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precursor solution consisting of stannic chloride (SnCl 4 .5H 2 0), ammonium fluoride (NH 4 F) and palladium chloride (PdCl 2). Optimization on the deposition parameters has been done in order to obtain high quality thin films. The effect of varying the fluorine content on the optical properties of Pd-F:SnO 2 thin films were studied. Data for transmittance and reflectance in the wavelength range from 300nm-2500nm was measured using the solid spec 3700DUV spectrophotometer. The calculated optical band gap of the as prepared thin films has been found to range from 3.8eV to 4.11eV. Fluorine incorporation for Pd-F:SnO 2 has been found to have a narrowing effect on the band gap, but at its higher concentration the band gap has been seen to increase. The band gap narrowing is due to the incorporation of Fions in the crystal lattice therefore giving rise to donor levels in the SnO 2 band gap which is an essential characteristic for the gas sensor applications. Both annealing and passivation have been found to have very insignificant change in optical band gap of Pd-F:SnO 2 .
Different thin films samples made of SnO 2 , F:SnO 2 , Pd: SnO 2 and and co-doped Pd-F: SnO 2 wer... more Different thin films samples made of SnO 2 , F:SnO 2 , Pd: SnO 2 and and co-doped Pd-F: SnO 2 were deposited at a substrate temperature of 450 o C using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450 o C. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO 2 and 3.8014eV for F:SnO 2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO 2 thin film for Pd:SnO 2 while for F:SnO 2 has been due to incorporation of Fions in the crystal lattice of SnO 2 which gives rise to donor levels in the SnO 2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value. The electrical resistivity was done by measuring the sheet resistance of the SnO 2 , Pd:SnO 2 , F:SnO 2 and Pd-F:SnO 2 thin films. The undoped SnO 2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO 2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO 2 results from substitution incorporation of Fions in the crystal lattice of SnO 2 thin films, instead of Oions which lead to an increase in free carrier concentration. The Pd-F:SnO 2 gas sensor device was tested for CO 2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO 2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO 2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth. This causes a decrement in adsorption properties of COand Ospecies by the annealed Pd-F: SnO 2 thin film. The sensitivity of passivated Pd-F: SnO 2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO 2 thin film was found to be within the range for gas sensing applications.
This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin f... more This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin films. Uniform TiO 2 and Nb 2 O 5 composites thin films were deposited on FTO coated glass substrate using electrophoretic deposition (EPD) technique. The EPD voltage of 35V (DC) and deposition time of 90s, were used for various volume fractions of Nb 2 O 5 in composites. Uniform and crack free composite films were successfully deposited using the EPD technique as shown by the SEM micrographs. The Hall Effect equipment was used to characterize the films through measurement of current and the Hall voltage. Current against Hall voltage plot for films of various volume fractions of Nb 2 O 5 were used to determine Hall coefficients and majority charge carrier density. The sign of Hall coefficient values revealed that TiO 2 /Nb 2 O 5 composite thin films had a net n-type polarity indicating electrons were the majority charge carrier in the composite films. The results showed that dye-sensitize...
In this study doped SnO 2 thin films have been prepared by spray pyrolysis technique using an alc... more In this study doped SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precursor solution consisting of stannic chloride (SnCl 4 .5H 2 O), ammonium fluoride (NH 4 F) and palladium chloride (PdCl 2). Optimization on the deposition parameters was done so as to obtain high quality thin films. The effect of varying the Fluorine content on the optoelectronic properties of F: SnO 2 thin films was studied. Data for transmittance and reflectance in the wavelength range from 300nm – 2500nm was obtained using the solid spec 3700DUV spectrophotometer. Electrical characterization of the thin films was done using the four point probe method at room temperature. Post deposition treatment of the thin films by annealing in air then passivating in nitrogen gas environment was done in a tube furnace at 450 0 C. Sheet resistivity for the as prepared F: SnO 2 was found to be 0.4599 Ωcm and 0.00075 Ωcm being the highest and lowest sheet resistivity at 22.74 at% F and 16....
This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin f... more This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin films. Uniform TiO 2 and Nb 2 O 5 composites thin films were deposited on FTO coated glass substrate using electrophoretic deposition (EPD) technique. The EPD voltage of 35V (DC) and deposition time of 90s, were used for various volume fractions of Nb 2 O 5 in composites. Uniform and crack free composite films were successfully deposited using the EPD technique as shown by the SEM micrographs. The Hall Effect equipment was used to characterize the films through measurement of current and the Hall voltage. Current against Hall voltage plot for films of various volume fractions of Nb 2 O 5 were used to determine Hall coefficients and majority charge carrier density. The sign of Hall coefficient values revealed that TiO 2 /Nb 2 O 5 composite thin films had a net n-type polarity indicating electrons were the majority charge carrier in the composite films. The results showed that dye-sensitize...
International Journal of Materials Science and Applications, 2014
Pd-F:SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precurso... more Pd-F:SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precursor solution consisting of stannic chloride (SnCl 4 .5H 2 0), ammonium fluoride (NH 4 F) and palladium chloride (PdCl 2). Optimization on the deposition parameters has been done in order to obtain high quality thin films. The effect of varying the fluorine content on the optical properties of Pd-F:SnO 2 thin films were studied. Data for transmittance and reflectance in the wavelength range from 300nm-2500nm was measured using the solid spec 3700DUV spectrophotometer. The calculated optical band gap of the as prepared thin films has been found to range from 3.8eV to 4.11eV. Fluorine incorporation for Pd-F:SnO 2 has been found to have a narrowing effect on the band gap, but at its higher concentration the band gap has been seen to increase. The band gap narrowing is due to the incorporation of Fions in the crystal lattice therefore giving rise to donor levels in the SnO 2 band gap which is an essential characteristic for the gas sensor applications. Both annealing and passivation have been found to have very insignificant change in optical band gap of Pd-F:SnO 2 .
Different thin films samples made of SnO 2 , F:SnO 2 , Pd: SnO 2 and and co-doped Pd-F: SnO 2 wer... more Different thin films samples made of SnO 2 , F:SnO 2 , Pd: SnO 2 and and co-doped Pd-F: SnO 2 were deposited at a substrate temperature of 450 o C using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450 o C. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO 2 and 3.8014eV for F:SnO 2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO 2 thin film for Pd:SnO 2 while for F:SnO 2 has been due to incorporation of Fions in the crystal lattice of SnO 2 which gives rise to donor levels in the SnO 2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value. The electrical resistivity was done by measuring the sheet resistance of the SnO 2 , Pd:SnO 2 , F:SnO 2 and Pd-F:SnO 2 thin films. The undoped SnO 2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO 2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO 2 results from substitution incorporation of Fions in the crystal lattice of SnO 2 thin films, instead of Oions which lead to an increase in free carrier concentration. The Pd-F:SnO 2 gas sensor device was tested for CO 2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO 2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO 2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth. This causes a decrement in adsorption properties of COand Ospecies by the annealed Pd-F: SnO 2 thin film. The sensitivity of passivated Pd-F: SnO 2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO 2 thin film was found to be within the range for gas sensing applications.
This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin f... more This paper reports the results of electrical characterization of TiO 2 /Nb 2 O 5 composite thin films. Uniform TiO 2 and Nb 2 O 5 composites thin films were deposited on FTO coated glass substrate using electrophoretic deposition (EPD) technique. The EPD voltage of 35V (DC) and deposition time of 90s, were used for various volume fractions of Nb 2 O 5 in composites. Uniform and crack free composite films were successfully deposited using the EPD technique as shown by the SEM micrographs. The Hall Effect equipment was used to characterize the films through measurement of current and the Hall voltage. Current against Hall voltage plot for films of various volume fractions of Nb 2 O 5 were used to determine Hall coefficients and majority charge carrier density. The sign of Hall coefficient values revealed that TiO 2 /Nb 2 O 5 composite thin films had a net n-type polarity indicating electrons were the majority charge carrier in the composite films. The results showed that dye-sensitize...
In this study doped SnO 2 thin films have been prepared by spray pyrolysis technique using an alc... more In this study doped SnO 2 thin films have been prepared by spray pyrolysis technique using an alcoholic precursor solution consisting of stannic chloride (SnCl 4 .5H 2 O), ammonium fluoride (NH 4 F) and palladium chloride (PdCl 2). Optimization on the deposition parameters was done so as to obtain high quality thin films. The effect of varying the Fluorine content on the optoelectronic properties of F: SnO 2 thin films was studied. Data for transmittance and reflectance in the wavelength range from 300nm – 2500nm was obtained using the solid spec 3700DUV spectrophotometer. Electrical characterization of the thin films was done using the four point probe method at room temperature. Post deposition treatment of the thin films by annealing in air then passivating in nitrogen gas environment was done in a tube furnace at 450 0 C. Sheet resistivity for the as prepared F: SnO 2 was found to be 0.4599 Ωcm and 0.00075 Ωcm being the highest and lowest sheet resistivity at 22.74 at% F and 16....
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