L. Chow | University of Central Florida (original) (raw)

Papers by L. Chow

The performance of CdTe/CdS/TCO/glass structure which is generally used as a solar cell depends o... more The performance of CdTe/CdS/TCO/glass structure which is generally used as a solar cell depends on the impurities incorporated in the system before and after electrodeposition of CdTe thin films. In this report we present a detailed investigation of this structure using secondary ion mass spectrometry(SIMS), x-ray microanalysis, x-ray diffraction(XRD), and scanning electron microscopy(SEM) to identify those impurities. We also discuss possible ways of minimizing or eliminating some of these impurities in order to improve the cell efficiency.

Thin Solid Films, 2008

A comprehensive study of the effect of cadmium sources on chemical bath deposited cadmium sulfide... more A comprehensive study of the effect of cadmium sources on chemical bath deposited cadmium sulfide thin films is reported. Four different cadmium sources; cadmium sulfate, cadmium chloride, cadmium iodide, and cadmium acetate have been used. The effect of cadmium sources on film optical/electrical properties as well as film thickness, composition, crystal structure, and surface morphology was studied. Film growth rate and band gap were found to be sensitive to the Cd source used. Films were found to be highly stoichiometric when cadmium chloride and cadmium iodide were used. The lowest resistivity and highest mobility and band gap obtained were in the case of cadmium sulfate. All films were found to be cubic, regardless of the Cd salt used.

Solar Energy Materials and Solar Cells, 2000

The potential of CdTe/CdS/Cd \V Zn V S structure as an alternative to CdTe/CdS structure in photo... more The potential of CdTe/CdS/Cd \V Zn V S structure as an alternative to CdTe/CdS structure in photovoltaic application has been demonstrated. The unoptimized solar cell structure grown on transparent conducting oxide coated soda lime glass of 3 mm thickness with no antire#ection coating yielded a 10% e$ciency. This e$ciency is the highest ever recorded in any Cd \V Zn V S "lm containing CdTe solar cells.

Thin Solid Films, 1999

We have obtained further insights into the CBD growth mechanisms of ZnS thin ®lms using an aqueou... more We have obtained further insights into the CBD growth mechanisms of ZnS thin ®lms using an aqueous medium containing an ammonium salt. At room temperature the optimum concentration of this salt has enabled us to increase the thickness of the ®lm by more than 400%. The optical transmission below the band edge of our best ®lm is also found to be excellent. q 1999 Elsevier Science S.A. All rights reserved.

Deposition of high quality zinc sulfide (ZnS) thin film over a large area is required if it is to... more Deposition of high quality zinc sulfide (ZnS) thin film over a large area is required if it is to be effectively used in electroluminescent devices, solar cells, and other optoelectronic devices. Of all deposition techniques, chemical bath deposition (CBD) is the least costly technique that meets the above requirements. Recently it is found that the growth of ZnS film, of thickness less than 100 nm in a single dip, by CBD is facilitated by the use of ammonia and hydrazine as complexing agents. Here we report that the thickness of the deposited ZnS film can be increased if ammonium salt is used as a buffer. We also present an analytical study to explain our results and to further understand the ZnS growth process in CBD.

ACS Symposium Series, 1997

Plasma-enhanced chemical vapor deposition has been used for the deposition of diamond and diamond... more Plasma-enhanced chemical vapor deposition has been used for the deposition of diamond and diamond-like thin films during the last decade with great success. Here we present experimental evidence that a chemical vapor deposition technique can also be used to synthesize ...

Journal of The Electrochemical Society, 1997

We report the optimization of CdS thin film grown by chemical bath deposition where homogenous re... more We report the optimization of CdS thin film grown by chemical bath deposition where homogenous reactions are minimized. The optimum parameters have enabled us to maximize the thickness of the deposited film in a single dip and to grow thicker films by periodically replenishing the concentration of reactants while the substrate remains continuously dipped in the reaction bath. Characterization results reveal the deposited CdS films exhibit improved optical and electrical properties. ABSTRACT We report the optimization of CdS thin film grown by chemical bath deposition where homogenous reactions are minimized. The optimum parameters have enabled us to maximize the thickness of the deposited film in a single dip and to grow thicker films by periodically replenishing the concentration of reactants while the substrate remains continuously dipped in the reaction bath. Characterization results reveal the deposited CdS films exhibit improved optical and electrical properties.

ECS Transactions, 2007

ABSTRACT A comprehensive study of the effect of the cadmium source on chemical bath deposited cad... more ABSTRACT A comprehensive study of the effect of the cadmium source on chemical bath deposited cadmium sulfide thin films is reported. Four different cadmium sources, namely cadmium sulfate, cadmium chloride, cadmium iodide, and cadmium acetate have been used. Single-dip, for 15 minutes, as well as multi-dip depositions (four successive depositions for 8-12 minutes each) were carried out at 70oC on quartz substrates. The effect of changing the cadmium source on the film optical/electrical properties as well as the film thickness was studied. Hall Effect measurements were carried out for all films as well as Rutherford Back Scattering (RBS), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM).

Materials Science and Engineering: B, 2009

2007 International Semiconductor Conference, 2007

Sn-doped ZnO nanorod arrays were synthesized by a novel method combining the aqueous solution pro... more Sn-doped ZnO nanorod arrays were synthesized by a novel method combining the aqueous solution process with post-growth rapid photothermal processing (RPP). The post-growth RPP of Sn-doped ZnO nanostrnctures at 700 degC in vacuum was found to result in a drastic decrease of the near-bandgap photoluminescence intensity. A comparison of the impact of RPP in Sn and AI doped samples is

2007 International Semiconductor Conference, 2007

A novel and efficient low-temperature aqueous chemical method has been used to synthesize a new g... more A novel and efficient low-temperature aqueous chemical method has been used to synthesize a new generation of smart and functional zinc oxide nanomaterials. The ZnO nanostructures are obtained and the physical and structural requirements of their applications in chemical sensors and solar cells are analyzed. Post-growth rapid photothermal annealing of nanostructures at 650°C in an atmosphere of N2 leads to the decrease in structure defects as compared to the as-grown nanostructures. The sensing behaviour of the nanostructured elements when exposed to 100 ppm ammonia is investigated

CAS 2011 Proceedings (2011 International Semiconductor Conference), 2011

For development of ZnO nanorods-based heterostructures an environmentally benign synthesis proces... more For development of ZnO nanorods-based heterostructures an environmentally benign synthesis process and fabrication route are required. Zinc oxide nanorod arrays have been grown on (0001) sapphire substrates by a rapid hydrothermal method (in 15 min) from a solution of zinc sulfate and sodium hydroxide. Two different synthesis regimes have been identified which give different morphologies of depositions shown by SEM. The structural properties of the depositions have been characterized by X-ray diffraction. Vibrational properties have been investigated by Micro-Raman spectroscopy. Detailed discussions of the experimental data are shown.

2009 International Semiconductor Conference, 2009

For development of individual ZnO microwire in hydrogen sensors an environmentally benign synthes... more For development of individual ZnO microwire in hydrogen sensors an environmentally benign synthesis process and fabrication route are required. Here we report a synthesis route for ZnO microwires using vapour phase process. Furthermore, our synthesis technique permits microwires to be transferred to other substrates. This offers the possibility of using focused ion beam instrument for handling. We fabricated a single microwire-based sensor and found ~4% sensitive hydrogen 200 ppm in the air at room temperature.

Thin Solid Films, 2011

We report a comparison of the role played by different sample treatments, namely, a low-temperatu... more We report a comparison of the role played by different sample treatments, namely, a low-temperature hydrothermal treatment by hot H 2 O vapor in an autoclave versus thermal annealing in air on the properties of ZnO films grown by electrochemical deposition (ECD). Scanning electron microscopy studies reveal a homogeneous micro-columnar morphology and changes in the film surface for the two different treatments. It is found that post-growth hydrothermal treatments of ECD ZnO films at 150°C under an aqueous environment enhance their structural and optical properties (photoluminescence, transmission, Raman spectra, etc.) similar to thermal annealing in air at higher temperatures (N 200°C). The modifications of the structural and optical properties of ZnO samples after thermal annealing in air in the temperature range of 150-600°C are discussed. The removal of chlorine from the films by the hydrothermal treatment was evidenced which could be the main reason for the improvement of the film quality. The observation of the enhanced photoluminescence peak at 380 nm demonstrates the superior properties of the hydrothermally treated ZnO films as compared to the films annealed in air ambient at the same or higher temperature. This post-growth hydrothermal treatment would be useful for the realization of high performance optoelectronic devices on flexible supports which might not withstand at high temperature annealing treatments.

Thin Solid Films, 2008

Undoped and Sn, Ni-doped nanostructured ZnO thin films were deposited on glass substrates using a... more Undoped and Sn, Ni-doped nanostructured ZnO thin films were deposited on glass substrates using a successive ionic layer adsorption and reaction (SILAR) method at room temperature. The SILAR deposited zinc oxide films have been rapid photothermal processing (RPP) at various temperatures to study the effect of annealing on the sensing properties. Structural, electrical and sensing properties were investigated by means of X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy, scanning electron microscopy, electrical resistivity, and sensitivity measurements. Microstructures of the deposited films were studied for different concentrations of dopants and zinc-complex solution and temperatures. The results of influence of growth processes, doping, and RPP on phase structure, surface morphology, particles size and resistivity values are presented and discussed. The average grain size determined from XRD patterns was 240, 220 and 265 Å for ZnO, Sn-ZnO and Ni-ZnO films, respectively. Moreover, electrical characterization of the sensors prepared from SILAR deposited nanostructured zinc oxide thin film has been carried out. The variation in resisitivity of the ZnO film sensors was obtained with doping and post-deposition rapid photothermal processing in vacuum and N 2 ambient. Electrical resistivity measurements showed semiconducting nature with room temperature resistivity 1.5 × 10 5 , 6.1 × 10 2 , 70 Ω cm for as-deposited ZnO, 4 at.% Ni-ZnO and 4 at.% Sn-ZnO, respectively. These values decreased to 1 × 10 4 , 2×10 2 , 30 Ω cm for RPP annealed films. The types of doping and temperatures of RPP were found to have an important role in determining the sensitivity and resolution of the NO 2 , NH 3 ZnO-based sensors. While the nanostructured ZnO sensor showed higher ammonia sensitivity than that of NO 2 , an enhanced NO 2 sensitivity was noticed with the ZnO films doped with 4 at.% Sn and higher NH 3 sensitivity was obtained by 4 at.% Ni doping of zinc oxide thin films.

The Journal of Physical Chemistry C, 2010

ZnO nanorods doped with Ag and Sb have been synthesized by a facile hydrothermal technique. Cryst... more ZnO nanorods doped with Ag and Sb have been synthesized by a facile hydrothermal technique. Crystal quality, morphology, chemical/electronic composition, local structure, and vibrational mode properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and micro-Raman spectroscopy. Evidence of dopant incorporation is demonstrated in the XPS measurements of both Sb-doped and Ag-doped ZnO nanorods. From XRD data, it was found that the doped ZnO nanorods have a lower degree of crystallinity. The lattice constants of doped ZnO nanorods were slightly larger than that of the pure samples.

Superlattices and Microstructures, 2008

We have investigated three-dimensional (3-D) architectures -microspheres and radial structures -b... more We have investigated three-dimensional (3-D) architectures -microspheres and radial structures -based on biopolymer-assisted self-assembly from one-dimensional ZnO nanorods. The developed method is simple, rapid and cost-effective and can be used for self-assembly of different complex superstructures. A possible model of 3-D architectures self-assembled with biopolymer assistance is presented using minimum energy considerations. Scanning electron microscopy, X-ray diffraction, energy dispersive Xray spectroscopy, transmission electron microscopy, micro-Raman spectroscopy and cathode luminescence investigations show that the novel 3-D architectures are built from high-purity ZnO nanorods with a wurtzite structure. The resulting radial structures show an intense ultraviolet (UV) cathode luminescence emission suggesting applications as UV light emitting diodes or lasers. Their structural characteristics endow them with a broad area of applications and offer a possibility to be used as fundamental low-dimensional building units. These building units open opportunities for the self-assembly of multifunctional nanostructured systems with applications in bioscience and nanomedicine, electronics and photonics.

Solid State Sciences, 2011

In this paper, a single ZnO microwire-based photodetector for the monitoring of ultraviolet (UV) ... more In this paper, a single ZnO microwire-based photodetector for the monitoring of ultraviolet (UV) radiation is described. Single crystal ZnO microwires were synthesized using a chemical vapor deposition (CVD) on the Si or Al 2 O 3 substrate. The UV photodetector was fabricated by using in-situ lift-out method in a focused ion beam system to manipulate individual zinc oxide microwire. The photodetector prototype consists of a single ZnO microwire (20 mm in length) and exhibits a response of w10 mA/W for UV light (365 nm) under 1 V bias. The transient response measurements revealed relatively fast response. The effect of oxygen adsorption and of different relative humidity conditions on the electronic transport through individual microwire is explored and discussed.

The performance of CdTe/CdS/TCO/glass structure which is generally used as a solar cell depends o... more The performance of CdTe/CdS/TCO/glass structure which is generally used as a solar cell depends on the impurities incorporated in the system before and after electrodeposition of CdTe thin films. In this report we present a detailed investigation of this structure using secondary ion mass spectrometry(SIMS), x-ray microanalysis, x-ray diffraction(XRD), and scanning electron microscopy(SEM) to identify those impurities. We also discuss possible ways of minimizing or eliminating some of these impurities in order to improve the cell efficiency.

Thin Solid Films, 2008

A comprehensive study of the effect of cadmium sources on chemical bath deposited cadmium sulfide... more A comprehensive study of the effect of cadmium sources on chemical bath deposited cadmium sulfide thin films is reported. Four different cadmium sources; cadmium sulfate, cadmium chloride, cadmium iodide, and cadmium acetate have been used. The effect of cadmium sources on film optical/electrical properties as well as film thickness, composition, crystal structure, and surface morphology was studied. Film growth rate and band gap were found to be sensitive to the Cd source used. Films were found to be highly stoichiometric when cadmium chloride and cadmium iodide were used. The lowest resistivity and highest mobility and band gap obtained were in the case of cadmium sulfate. All films were found to be cubic, regardless of the Cd salt used.

Solar Energy Materials and Solar Cells, 2000

The potential of CdTe/CdS/Cd \V Zn V S structure as an alternative to CdTe/CdS structure in photo... more The potential of CdTe/CdS/Cd \V Zn V S structure as an alternative to CdTe/CdS structure in photovoltaic application has been demonstrated. The unoptimized solar cell structure grown on transparent conducting oxide coated soda lime glass of 3 mm thickness with no antire#ection coating yielded a 10% e$ciency. This e$ciency is the highest ever recorded in any Cd \V Zn V S "lm containing CdTe solar cells.

Thin Solid Films, 1999

We have obtained further insights into the CBD growth mechanisms of ZnS thin ®lms using an aqueou... more We have obtained further insights into the CBD growth mechanisms of ZnS thin ®lms using an aqueous medium containing an ammonium salt. At room temperature the optimum concentration of this salt has enabled us to increase the thickness of the ®lm by more than 400%. The optical transmission below the band edge of our best ®lm is also found to be excellent. q 1999 Elsevier Science S.A. All rights reserved.

Deposition of high quality zinc sulfide (ZnS) thin film over a large area is required if it is to... more Deposition of high quality zinc sulfide (ZnS) thin film over a large area is required if it is to be effectively used in electroluminescent devices, solar cells, and other optoelectronic devices. Of all deposition techniques, chemical bath deposition (CBD) is the least costly technique that meets the above requirements. Recently it is found that the growth of ZnS film, of thickness less than 100 nm in a single dip, by CBD is facilitated by the use of ammonia and hydrazine as complexing agents. Here we report that the thickness of the deposited ZnS film can be increased if ammonium salt is used as a buffer. We also present an analytical study to explain our results and to further understand the ZnS growth process in CBD.

ACS Symposium Series, 1997

Plasma-enhanced chemical vapor deposition has been used for the deposition of diamond and diamond... more Plasma-enhanced chemical vapor deposition has been used for the deposition of diamond and diamond-like thin films during the last decade with great success. Here we present experimental evidence that a chemical vapor deposition technique can also be used to synthesize ...

Journal of The Electrochemical Society, 1997

We report the optimization of CdS thin film grown by chemical bath deposition where homogenous re... more We report the optimization of CdS thin film grown by chemical bath deposition where homogenous reactions are minimized. The optimum parameters have enabled us to maximize the thickness of the deposited film in a single dip and to grow thicker films by periodically replenishing the concentration of reactants while the substrate remains continuously dipped in the reaction bath. Characterization results reveal the deposited CdS films exhibit improved optical and electrical properties. ABSTRACT We report the optimization of CdS thin film grown by chemical bath deposition where homogenous reactions are minimized. The optimum parameters have enabled us to maximize the thickness of the deposited film in a single dip and to grow thicker films by periodically replenishing the concentration of reactants while the substrate remains continuously dipped in the reaction bath. Characterization results reveal the deposited CdS films exhibit improved optical and electrical properties.

ECS Transactions, 2007

ABSTRACT A comprehensive study of the effect of the cadmium source on chemical bath deposited cad... more ABSTRACT A comprehensive study of the effect of the cadmium source on chemical bath deposited cadmium sulfide thin films is reported. Four different cadmium sources, namely cadmium sulfate, cadmium chloride, cadmium iodide, and cadmium acetate have been used. Single-dip, for 15 minutes, as well as multi-dip depositions (four successive depositions for 8-12 minutes each) were carried out at 70oC on quartz substrates. The effect of changing the cadmium source on the film optical/electrical properties as well as the film thickness was studied. Hall Effect measurements were carried out for all films as well as Rutherford Back Scattering (RBS), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM).

Materials Science and Engineering: B, 2009

2007 International Semiconductor Conference, 2007

Sn-doped ZnO nanorod arrays were synthesized by a novel method combining the aqueous solution pro... more Sn-doped ZnO nanorod arrays were synthesized by a novel method combining the aqueous solution process with post-growth rapid photothermal processing (RPP). The post-growth RPP of Sn-doped ZnO nanostrnctures at 700 degC in vacuum was found to result in a drastic decrease of the near-bandgap photoluminescence intensity. A comparison of the impact of RPP in Sn and AI doped samples is

2007 International Semiconductor Conference, 2007

A novel and efficient low-temperature aqueous chemical method has been used to synthesize a new g... more A novel and efficient low-temperature aqueous chemical method has been used to synthesize a new generation of smart and functional zinc oxide nanomaterials. The ZnO nanostructures are obtained and the physical and structural requirements of their applications in chemical sensors and solar cells are analyzed. Post-growth rapid photothermal annealing of nanostructures at 650°C in an atmosphere of N2 leads to the decrease in structure defects as compared to the as-grown nanostructures. The sensing behaviour of the nanostructured elements when exposed to 100 ppm ammonia is investigated

CAS 2011 Proceedings (2011 International Semiconductor Conference), 2011

For development of ZnO nanorods-based heterostructures an environmentally benign synthesis proces... more For development of ZnO nanorods-based heterostructures an environmentally benign synthesis process and fabrication route are required. Zinc oxide nanorod arrays have been grown on (0001) sapphire substrates by a rapid hydrothermal method (in 15 min) from a solution of zinc sulfate and sodium hydroxide. Two different synthesis regimes have been identified which give different morphologies of depositions shown by SEM. The structural properties of the depositions have been characterized by X-ray diffraction. Vibrational properties have been investigated by Micro-Raman spectroscopy. Detailed discussions of the experimental data are shown.

2009 International Semiconductor Conference, 2009

For development of individual ZnO microwire in hydrogen sensors an environmentally benign synthes... more For development of individual ZnO microwire in hydrogen sensors an environmentally benign synthesis process and fabrication route are required. Here we report a synthesis route for ZnO microwires using vapour phase process. Furthermore, our synthesis technique permits microwires to be transferred to other substrates. This offers the possibility of using focused ion beam instrument for handling. We fabricated a single microwire-based sensor and found ~4% sensitive hydrogen 200 ppm in the air at room temperature.

Thin Solid Films, 2011

We report a comparison of the role played by different sample treatments, namely, a low-temperatu... more We report a comparison of the role played by different sample treatments, namely, a low-temperature hydrothermal treatment by hot H 2 O vapor in an autoclave versus thermal annealing in air on the properties of ZnO films grown by electrochemical deposition (ECD). Scanning electron microscopy studies reveal a homogeneous micro-columnar morphology and changes in the film surface for the two different treatments. It is found that post-growth hydrothermal treatments of ECD ZnO films at 150°C under an aqueous environment enhance their structural and optical properties (photoluminescence, transmission, Raman spectra, etc.) similar to thermal annealing in air at higher temperatures (N 200°C). The modifications of the structural and optical properties of ZnO samples after thermal annealing in air in the temperature range of 150-600°C are discussed. The removal of chlorine from the films by the hydrothermal treatment was evidenced which could be the main reason for the improvement of the film quality. The observation of the enhanced photoluminescence peak at 380 nm demonstrates the superior properties of the hydrothermally treated ZnO films as compared to the films annealed in air ambient at the same or higher temperature. This post-growth hydrothermal treatment would be useful for the realization of high performance optoelectronic devices on flexible supports which might not withstand at high temperature annealing treatments.

Thin Solid Films, 2008

Undoped and Sn, Ni-doped nanostructured ZnO thin films were deposited on glass substrates using a... more Undoped and Sn, Ni-doped nanostructured ZnO thin films were deposited on glass substrates using a successive ionic layer adsorption and reaction (SILAR) method at room temperature. The SILAR deposited zinc oxide films have been rapid photothermal processing (RPP) at various temperatures to study the effect of annealing on the sensing properties. Structural, electrical and sensing properties were investigated by means of X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy, scanning electron microscopy, electrical resistivity, and sensitivity measurements. Microstructures of the deposited films were studied for different concentrations of dopants and zinc-complex solution and temperatures. The results of influence of growth processes, doping, and RPP on phase structure, surface morphology, particles size and resistivity values are presented and discussed. The average grain size determined from XRD patterns was 240, 220 and 265 Å for ZnO, Sn-ZnO and Ni-ZnO films, respectively. Moreover, electrical characterization of the sensors prepared from SILAR deposited nanostructured zinc oxide thin film has been carried out. The variation in resisitivity of the ZnO film sensors was obtained with doping and post-deposition rapid photothermal processing in vacuum and N 2 ambient. Electrical resistivity measurements showed semiconducting nature with room temperature resistivity 1.5 × 10 5 , 6.1 × 10 2 , 70 Ω cm for as-deposited ZnO, 4 at.% Ni-ZnO and 4 at.% Sn-ZnO, respectively. These values decreased to 1 × 10 4 , 2×10 2 , 30 Ω cm for RPP annealed films. The types of doping and temperatures of RPP were found to have an important role in determining the sensitivity and resolution of the NO 2 , NH 3 ZnO-based sensors. While the nanostructured ZnO sensor showed higher ammonia sensitivity than that of NO 2 , an enhanced NO 2 sensitivity was noticed with the ZnO films doped with 4 at.% Sn and higher NH 3 sensitivity was obtained by 4 at.% Ni doping of zinc oxide thin films.

The Journal of Physical Chemistry C, 2010

ZnO nanorods doped with Ag and Sb have been synthesized by a facile hydrothermal technique. Cryst... more ZnO nanorods doped with Ag and Sb have been synthesized by a facile hydrothermal technique. Crystal quality, morphology, chemical/electronic composition, local structure, and vibrational mode properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and micro-Raman spectroscopy. Evidence of dopant incorporation is demonstrated in the XPS measurements of both Sb-doped and Ag-doped ZnO nanorods. From XRD data, it was found that the doped ZnO nanorods have a lower degree of crystallinity. The lattice constants of doped ZnO nanorods were slightly larger than that of the pure samples.

Superlattices and Microstructures, 2008

We have investigated three-dimensional (3-D) architectures -microspheres and radial structures -b... more We have investigated three-dimensional (3-D) architectures -microspheres and radial structures -based on biopolymer-assisted self-assembly from one-dimensional ZnO nanorods. The developed method is simple, rapid and cost-effective and can be used for self-assembly of different complex superstructures. A possible model of 3-D architectures self-assembled with biopolymer assistance is presented using minimum energy considerations. Scanning electron microscopy, X-ray diffraction, energy dispersive Xray spectroscopy, transmission electron microscopy, micro-Raman spectroscopy and cathode luminescence investigations show that the novel 3-D architectures are built from high-purity ZnO nanorods with a wurtzite structure. The resulting radial structures show an intense ultraviolet (UV) cathode luminescence emission suggesting applications as UV light emitting diodes or lasers. Their structural characteristics endow them with a broad area of applications and offer a possibility to be used as fundamental low-dimensional building units. These building units open opportunities for the self-assembly of multifunctional nanostructured systems with applications in bioscience and nanomedicine, electronics and photonics.

Solid State Sciences, 2011

In this paper, a single ZnO microwire-based photodetector for the monitoring of ultraviolet (UV) ... more In this paper, a single ZnO microwire-based photodetector for the monitoring of ultraviolet (UV) radiation is described. Single crystal ZnO microwires were synthesized using a chemical vapor deposition (CVD) on the Si or Al 2 O 3 substrate. The UV photodetector was fabricated by using in-situ lift-out method in a focused ion beam system to manipulate individual zinc oxide microwire. The photodetector prototype consists of a single ZnO microwire (20 mm in length) and exhibits a response of w10 mA/W for UV light (365 nm) under 1 V bias. The transient response measurements revealed relatively fast response. The effect of oxygen adsorption and of different relative humidity conditions on the electronic transport through individual microwire is explored and discussed.