p H determination is a strong prerequisite for many biochemical and biological processes. We used... more p H determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D=300 nm and L=10 μm, to 58 mV/pH for D=50 nm and L=1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer and NaCl solutions.
... Muzaffer Çakar, Nezir Yıldırım, Şukru Karataş, Cabir Temirci, Abdulmecit Türüt. ... Therefore... more ... Muzaffer Çakar, Nezir Yıldırım, Şukru Karataş, Cabir Temirci, Abdulmecit Türüt. ... Therefore, the SBH determined from the zero bias intercept, assuming thermionic emission as the current transport ... CJHuang, S.Han, D.Groze, A.Turak, and ZHLu, Organic light-emitting devices with ...
An overview of our recent results on characterization and modification of high-resistivity n-type... more An overview of our recent results on characterization and modification of high-resistivity n-type bulk zinc oxide samples, grown by hydrothermal techniques, is given. Three specific topics are addressed; (i) the role of lithium (Li) as an electrically compensating impurity, (ii) extrinsic n-type doping by hydrogen implantation, and (iii) influence of annealing conditions on deep band emission. In (i), furnace annealing of as-grown samples at temperatures above ∼800 °C is shown to cause out-diffusion of residual Li impurities and concurrently, the resistivity decreases. After annealing at 1400 °C, a resistivity close to 10−1 Ωcm is obtained and the Li content is reduced from above 1017 cm−3 to the mid 1015 cm−3 range, providing evidence for the crucial role of Li as an electrically compensating impurity. For ion-implanted samples, vacancy clusters evolve during post-implant flash lamp annealing (20 ms duration) and these clusters appear to trap and deactivate Li with a resulting improvement of the n-type conductivity. However, these clusters have a limited stability and start to dissociate already after 1h at 900 °C, accompanied by a decrease in the conductivity. For topic (ii), n-type doping by hydrogen implantation is shown to enhance the conductivity by about 5 orders of magnitude already in the as-implanted state. Despite substantial loss of hydrogen, the conductivity remains stable, or even increases, after annealing up to ≥600 °C, and necessary conditions for doping by hydrogen are discussed. In (iii), the origin of the commonly observed deep band emission from monocrystalline zinc oxide is investigated using a concept of annealing as-grown samples in different atmospheres. A strong influence by the atmosphere and temperature is observed and the results can be interpreted in terms of dominant effects on the emission by vacancy-related defects.
ABSTRACT Energy levels and wave functions of ground and excited states of an exciton are calculat... more ABSTRACT Energy levels and wave functions of ground and excited states of an exciton are calculated by the method of imaginary time. Energy levels as functions of radius of single and double wall nanotube are studied. Asymptotic behavior of energy levels at large and small values of the radius using perturbation theory and adiabatic approximation is considered. Spatially indirect exciton in semiconductor nanowire is also investigated. Experimental result from high quality reproducible ZnO nanowires grown by low temperature chemical engineering is presented. State of the art high brightness white light emitting diodes (HB-LEDs) are demonstrated from the grown ZnO nano-wires. The color temperature and color rendering index (CRI) of the HB-LEDs values was found to be (3250 K, 82), and (14000 K, 93), for the best LEDs, which means that the quality of light is superior to one obtained from GaN LEDs available on the market today. The role of VZn and VO on the emission responsible for the white light band as well as the peak position of this important wide band is thoroughly investigated in a systematic way.
ABSTRACT ZnO nanostructures were grown by thermal evaporation technique on (001) Si substrate and... more ABSTRACT ZnO nanostructures were grown by thermal evaporation technique on (001) Si substrate and were characterized by photoluminescence measurements, scanning electron microscope and x-ray measurements. The results show that the formation of ZnO nanostructures is strongly influenced by the growth conditions. By optimizing the growth conditions, orientated ZnO nanorods with a diameter of around 300 nm and lengths of 20–35 μm have been achieved, and they show excellent optical properties. The laser action is observed at room temperature by using optical pumping.
A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in... more A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc-and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are ...
Recently zinc oxide (ZnO) has drawn attention as it exhibits promising properties for making opto... more Recently zinc oxide (ZnO) has drawn attention as it exhibits promising properties for making optoelectronic devices, biosensors. In this paper we will present our recent results from research work on the fabrication of light emitting diodes (LEDs) based on n-ZnO nanorods grown on p-Si by a low temperature chemical approach. The ideality factor of the p- Si/n-ZnO junctions was found
An overview of our recent results on characterization and modification of high-resistivity n-type... more An overview of our recent results on characterization and modification of high-resistivity n-type bulk zinc oxide samples, grown by hydrothermal techniques, is given. Three specific topics are addressed; (i) the role of lithium (Li) as an electrically compensating impurity, (ii) extrinsic n-type doping by hydrogen implantation, and (iii) influence of annealing conditions on deep band emission. In (i), furnace annealing of as-grown samples at temperatures above ∼800 °C is shown to cause out-diffusion of residual Li impurities and concurrently, the resistivity decreases. After annealing at 1400 °C, a resistivity close to 10−1 Ωcm is obtained and the Li content is reduced from above 1017 cm−3 to the mid 1015 cm−3 range, providing evidence for the crucial role of Li as an electrically compensating impurity. For ion-implanted samples, vacancy clusters evolve during post-implant flash lamp annealing (20 ms duration) and these clusters appear to trap and deactivate Li with a resulting impr...
A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in... more A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc-and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are ...
p H determination is a strong prerequisite for many biochemical and biological processes. We used... more p H determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D=300 nm and L=10 μm, to 58 mV/pH for D=50 nm and L=1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer ...
p H determination is a strong prerequisite for many biochemical and biological processes. We used... more p H determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D=300 nm and L=10 μm, to 58 mV/pH for D=50 nm and L=1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer and NaCl solutions.
... Muzaffer Çakar, Nezir Yıldırım, Şukru Karataş, Cabir Temirci, Abdulmecit Türüt. ... Therefore... more ... Muzaffer Çakar, Nezir Yıldırım, Şukru Karataş, Cabir Temirci, Abdulmecit Türüt. ... Therefore, the SBH determined from the zero bias intercept, assuming thermionic emission as the current transport ... CJHuang, S.Han, D.Groze, A.Turak, and ZHLu, Organic light-emitting devices with ...
An overview of our recent results on characterization and modification of high-resistivity n-type... more An overview of our recent results on characterization and modification of high-resistivity n-type bulk zinc oxide samples, grown by hydrothermal techniques, is given. Three specific topics are addressed; (i) the role of lithium (Li) as an electrically compensating impurity, (ii) extrinsic n-type doping by hydrogen implantation, and (iii) influence of annealing conditions on deep band emission. In (i), furnace annealing of as-grown samples at temperatures above ∼800 °C is shown to cause out-diffusion of residual Li impurities and concurrently, the resistivity decreases. After annealing at 1400 °C, a resistivity close to 10−1 Ωcm is obtained and the Li content is reduced from above 1017 cm−3 to the mid 1015 cm−3 range, providing evidence for the crucial role of Li as an electrically compensating impurity. For ion-implanted samples, vacancy clusters evolve during post-implant flash lamp annealing (20 ms duration) and these clusters appear to trap and deactivate Li with a resulting improvement of the n-type conductivity. However, these clusters have a limited stability and start to dissociate already after 1h at 900 °C, accompanied by a decrease in the conductivity. For topic (ii), n-type doping by hydrogen implantation is shown to enhance the conductivity by about 5 orders of magnitude already in the as-implanted state. Despite substantial loss of hydrogen, the conductivity remains stable, or even increases, after annealing up to ≥600 °C, and necessary conditions for doping by hydrogen are discussed. In (iii), the origin of the commonly observed deep band emission from monocrystalline zinc oxide is investigated using a concept of annealing as-grown samples in different atmospheres. A strong influence by the atmosphere and temperature is observed and the results can be interpreted in terms of dominant effects on the emission by vacancy-related defects.
ABSTRACT Energy levels and wave functions of ground and excited states of an exciton are calculat... more ABSTRACT Energy levels and wave functions of ground and excited states of an exciton are calculated by the method of imaginary time. Energy levels as functions of radius of single and double wall nanotube are studied. Asymptotic behavior of energy levels at large and small values of the radius using perturbation theory and adiabatic approximation is considered. Spatially indirect exciton in semiconductor nanowire is also investigated. Experimental result from high quality reproducible ZnO nanowires grown by low temperature chemical engineering is presented. State of the art high brightness white light emitting diodes (HB-LEDs) are demonstrated from the grown ZnO nano-wires. The color temperature and color rendering index (CRI) of the HB-LEDs values was found to be (3250 K, 82), and (14000 K, 93), for the best LEDs, which means that the quality of light is superior to one obtained from GaN LEDs available on the market today. The role of VZn and VO on the emission responsible for the white light band as well as the peak position of this important wide band is thoroughly investigated in a systematic way.
ABSTRACT ZnO nanostructures were grown by thermal evaporation technique on (001) Si substrate and... more ABSTRACT ZnO nanostructures were grown by thermal evaporation technique on (001) Si substrate and were characterized by photoluminescence measurements, scanning electron microscope and x-ray measurements. The results show that the formation of ZnO nanostructures is strongly influenced by the growth conditions. By optimizing the growth conditions, orientated ZnO nanorods with a diameter of around 300 nm and lengths of 20–35 μm have been achieved, and they show excellent optical properties. The laser action is observed at room temperature by using optical pumping.
A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in... more A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc-and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are ...
Recently zinc oxide (ZnO) has drawn attention as it exhibits promising properties for making opto... more Recently zinc oxide (ZnO) has drawn attention as it exhibits promising properties for making optoelectronic devices, biosensors. In this paper we will present our recent results from research work on the fabrication of light emitting diodes (LEDs) based on n-ZnO nanorods grown on p-Si by a low temperature chemical approach. The ideality factor of the p- Si/n-ZnO junctions was found
An overview of our recent results on characterization and modification of high-resistivity n-type... more An overview of our recent results on characterization and modification of high-resistivity n-type bulk zinc oxide samples, grown by hydrothermal techniques, is given. Three specific topics are addressed; (i) the role of lithium (Li) as an electrically compensating impurity, (ii) extrinsic n-type doping by hydrogen implantation, and (iii) influence of annealing conditions on deep band emission. In (i), furnace annealing of as-grown samples at temperatures above ∼800 °C is shown to cause out-diffusion of residual Li impurities and concurrently, the resistivity decreases. After annealing at 1400 °C, a resistivity close to 10−1 Ωcm is obtained and the Li content is reduced from above 1017 cm−3 to the mid 1015 cm−3 range, providing evidence for the crucial role of Li as an electrically compensating impurity. For ion-implanted samples, vacancy clusters evolve during post-implant flash lamp annealing (20 ms duration) and these clusters appear to trap and deactivate Li with a resulting impr...
A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in... more A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc-and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are ...
p H determination is a strong prerequisite for many biochemical and biological processes. We used... more p H determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D=300 nm and L=10 μm, to 58 mV/pH for D=50 nm and L=1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer ...
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