Jack Hudson - Academia.edu (original) (raw)

Papers by Jack Hudson

IEEE Transactions on Appiled Superconductivity, 2003

High quality single Josephson junctions and junction arrays with 10 junctions in series have been... more High quality single Josephson junctions and junction arrays with 10 junctions in series have been fabricated using masked proton beam irradiation damage technology. Monte Carlo simulation of the irradiation damage profile underneath the metal mask has been carried out systematically to guide the metal mask structure design. A high resolution and high aspect ratio metal mask opening was fabricated by focused 30 keV Ga ion beam milling. Various nonconducting oxide buffer layers have been investigated for a Ga contamination free mask fabrication. A contamination free irradiation process and subsequent removal of metal mask after ion irradiation are the keys for the improved properties of junctions fabricated with YBCO.

Current Applied Physics, 2009

ABSTRACT We have investigated biological functionality of immobilized enzyme structures according... more ABSTRACT We have investigated biological functionality of immobilized enzyme structures according to the immobilizing routes and the surface properties. Horse radish peroxidase (HRP) was immobilized on various solid surfaces such as gold, SiO2, sapphire and anodized aluminum oxide (AAO) membrane via non-specific adsorption, avidin-mediated and biotin/avidin-mediated layer-by-layer (LBL) assembly. The catalytic activity as a measure of biological functionality, of the biotin-HRP immobilized by avidin-mediated LBL assembly was found to be better than that of the directly adsorbed HRP on the surfaces of gold, SiO2, sapphire and AAO due to the easy accessibility of reactants to active sites as well as the retention of three dimensional native structure of enzyme for bioactive functionality. In addition, the catalytic activity of the biotin-HRP in LBL-assembled avidin/biotin-HRP on AAO membrane was found to be highly better than that on other substrates due to the increasing amount of immobilized HRP which can be attributed to the high surface area of the substrate. SEM images show that the functional avidin/biotin-HRP enzyme structures were successfully realized by a sequential process of non-specific adsorption and LBL assembly via biotin–avidin interaction.

IEEE Transactions on Nanotechnology - IEEE TRANS NANOTECHNOL, 2008

Nanogripper structures using aligned multiwall carbon nanotubes (MWCNTs) are demonstrated and the... more Nanogripper structures using aligned multiwall carbon nanotubes (MWCNTs) are demonstrated and their electromechanical properties have been studied in this paper. The balance of electrostatic force, together with elastostatic force and van der Waals force determines the driving conditions. A triode structure drastically reduces the bias between two moving parts, which consist of MWCNTs. Low bias also enables low power consumption as well as the reduction of electrical damage to an object. The moving parts can keep the same state without any applied biases after bending and connection. This also enables power saving during driving. The device can be a base structure for various nanorobotic or other nanoelectromechanical devices.

IEEE Transactions on Appiled Superconductivity, 1997

Crystal Growth & Design, 2008

This paper reports the facile synthesis of indium hydroxide nanospheres, nanoflowers, microcubes,... more This paper reports the facile synthesis of indium hydroxide nanospheres, nanoflowers, microcubes, and nanorods using a solvothermal method at 240°C for 18 h in an ethanol solution of indium acetate with the directing surfactants of ethylenediamine, acetic acid, and oleic acid. After calcination of as-synthesized indium hydroxide products at 500°C for 4 h, corresponding indium oxide nanostructures were also obtained with sizes and morphologies similar to the indium hydroxide products. The phase compositions and morphologies of the resulting samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. On the basis of our findings, we propose a surfactant-assisted self-assembly formation mechanism to account for their formation processes. Room temperature photoluminescence was further carried out on the indium oxide samples to investigate their optical properties.

Nanotechnology, 2009

We demonstrate the effect of surface chemical dynamics on carrier transport and recombination pro... more We demonstrate the effect of surface chemical dynamics on carrier transport and recombination processes of electron-hole pairs in ZnO nanowire field effect transistors. We have found that the electrical conductance decreases and the threshold voltages shift in a positive gate voltage direction, as electrical characteristics are measured repeatedly. We associate this with the enhancement of oxygen adsorption by capturing electrons from the induced current during the probing. This results in an overall depletion of electrons and thus causes the positive shift in threshold voltages associated with the origin and width of characteristic hysteresis loops. In addition, the surface environment dependence of the photo-response related to a recombination process in ZnO nanowires is discussed in terms of the surface chemical reaction and band bending.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2006

We demonstrate the fabrication of sub-10-nm high aspect ratio electron beam patterning of ZnO at ... more We demonstrate the fabrication of sub-10-nm high aspect ratio electron beam patterning of ZnO at the center as well as corners of the 500 m square main deflection field using a negative tone zinc naphthenate resist. After electron beam exposure, the resist was developed in toluene, resulting in high-resolution patterns as small as 7 nm with an aspect ratio of ϳ10 in the center as well as at the corners of the main field. The line edge roughness ͑3͒ of these lines shows roughness with fluctuations of about 2.8 nm; thus making it the smallest value of the line edge roughness measured so far for any electron beam resist. Heating the structures at 500°C resulted in reduction of feature sizes to ϳ5 nm and in the formation of crystalline ZnO. Such sub-10-nm high aspect ratio patterning within the main deflection field is an important step to enable full-wafer-level nanofabrication.

IEEE Transactions on Appiled Superconductivity, 2003

We have successfully fabricated high quality Josephson junctions in MgB 2 thin films by a combina... more We have successfully fabricated high quality Josephson junctions in MgB 2 thin films by a combination of 30 kV focused Ga ion beam nanolithography and 50 keV proton ion beam irradiation. The junctions show resistively shunted junction like current-voltage characteristics with additional excess current. Monte Carlo simulation results for the optimized mask structure and experimental results for the dc and ac Josephson effects are presented. This technique is particularly useful for prototyping devices due to its simplicity and flexibility of fabrication and has a great potential for high-density integration.

Journal of Nanoscience and Nanotechnology, 2012

Electrohydrodynamic lithography (EHL) is one of several unusual lithographic techniques for fabri... more Electrohydrodynamic lithography (EHL) is one of several unusual lithographic techniques for fabricating sub-micrometer structures over a large area. EHL uses the electrohydrodynamic (EHD) film instability induced by a laterally modulated electric field, which allows it to fabricate not only general organic structures but also structures of various components, such as diblock copolymers and inorganic materials, without contact between the resist and the stamp. Furthermore, EHL is a very special lithographic technique in that diverse structures are fabricated from one stamp via electric field modulation. The electric field is controlled by the replication time, air layer thickness, etc. A replicated inorganic structure was demonstrated from a hexagonal hole and line arrays. The heat treatment of the replicated pattern was carried out to obtain the crystalline phase, after which the samples were characterized via Raman spectroscopy. These values were ascertained using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The results will be useful in providing a facile route for patterning functional metal oxides over a large area. Such a technique can be used to produce photovoltaic cells, memory devices, display devices, etc.

Chemical Communications, 2010

Single crystalline MoO(3) and Cu(0.33)MoO(3) nanorods have been synthesized in large quantities v... more Single crystalline MoO(3) and Cu(0.33)MoO(3) nanorods have been synthesized in large quantities via hydrothermal route, which exhibit unprecedented photocatalytic performance for the decomposition of Toluidine blue "O" (TBO) and chlorobenzene both under visible and UV light irradiation.

Journal of the American Chemical Society, 2008

Recently, because of the record-high oil prices and the serious global warming problems, the deve... more Recently, because of the record-high oil prices and the serious global warming problems, the development of hybrid electric vehicles (HEVs) is under the spotlight and lithium ion batteries (LIBs) have been a strong candidate for powering them. One of the key safety issues in LIBs for HEVs would be the dendritic lithium growth on the anode surface at high charging current because the conventional carbonous materials approach almost 0 V vs Li at the end of Li insertion. 1 Therefore, a fundamental solution is to use an electrochemical redox couple with higher equilibrium potentials, which makes Li formation thermodynamically less favorable. Among the candidates, Li 4 Ti 5 O 12 using the Ti 4+ /Ti 3+ redox couple (ca. 1.5 V vs Li) has showed promising electrochemical properties with structural and chemical stabilities vis-à-vis to the electrolyte. 2 The electronic structure of Li 4 Ti 5 O 12 characterized by empty Ti 3d-states with a band gap energy of ∼2 eV gives an insulating character to this material. 3 Therefore, the high current properties of Li 4 Ti 5 O 12 might not be sufficient for high current applications before any materials modifications.

IEEE Transactions on Appiled Superconductivity, 2003

High quality single Josephson junctions and junction arrays with 10 junctions in series have been... more High quality single Josephson junctions and junction arrays with 10 junctions in series have been fabricated using masked proton beam irradiation damage technology. Monte Carlo simulation of the irradiation damage profile underneath the metal mask has been carried out systematically to guide the metal mask structure design. A high resolution and high aspect ratio metal mask opening was fabricated by focused 30 keV Ga ion beam milling. Various nonconducting oxide buffer layers have been investigated for a Ga contamination free mask fabrication. A contamination free irradiation process and subsequent removal of metal mask after ion irradiation are the keys for the improved properties of junctions fabricated with YBCO.

Current Applied Physics, 2009

ABSTRACT We have investigated biological functionality of immobilized enzyme structures according... more ABSTRACT We have investigated biological functionality of immobilized enzyme structures according to the immobilizing routes and the surface properties. Horse radish peroxidase (HRP) was immobilized on various solid surfaces such as gold, SiO2, sapphire and anodized aluminum oxide (AAO) membrane via non-specific adsorption, avidin-mediated and biotin/avidin-mediated layer-by-layer (LBL) assembly. The catalytic activity as a measure of biological functionality, of the biotin-HRP immobilized by avidin-mediated LBL assembly was found to be better than that of the directly adsorbed HRP on the surfaces of gold, SiO2, sapphire and AAO due to the easy accessibility of reactants to active sites as well as the retention of three dimensional native structure of enzyme for bioactive functionality. In addition, the catalytic activity of the biotin-HRP in LBL-assembled avidin/biotin-HRP on AAO membrane was found to be highly better than that on other substrates due to the increasing amount of immobilized HRP which can be attributed to the high surface area of the substrate. SEM images show that the functional avidin/biotin-HRP enzyme structures were successfully realized by a sequential process of non-specific adsorption and LBL assembly via biotin–avidin interaction.

IEEE Transactions on Nanotechnology - IEEE TRANS NANOTECHNOL, 2008

Nanogripper structures using aligned multiwall carbon nanotubes (MWCNTs) are demonstrated and the... more Nanogripper structures using aligned multiwall carbon nanotubes (MWCNTs) are demonstrated and their electromechanical properties have been studied in this paper. The balance of electrostatic force, together with elastostatic force and van der Waals force determines the driving conditions. A triode structure drastically reduces the bias between two moving parts, which consist of MWCNTs. Low bias also enables low power consumption as well as the reduction of electrical damage to an object. The moving parts can keep the same state without any applied biases after bending and connection. This also enables power saving during driving. The device can be a base structure for various nanorobotic or other nanoelectromechanical devices.

IEEE Transactions on Appiled Superconductivity, 1997

Crystal Growth & Design, 2008

This paper reports the facile synthesis of indium hydroxide nanospheres, nanoflowers, microcubes,... more This paper reports the facile synthesis of indium hydroxide nanospheres, nanoflowers, microcubes, and nanorods using a solvothermal method at 240°C for 18 h in an ethanol solution of indium acetate with the directing surfactants of ethylenediamine, acetic acid, and oleic acid. After calcination of as-synthesized indium hydroxide products at 500°C for 4 h, corresponding indium oxide nanostructures were also obtained with sizes and morphologies similar to the indium hydroxide products. The phase compositions and morphologies of the resulting samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. On the basis of our findings, we propose a surfactant-assisted self-assembly formation mechanism to account for their formation processes. Room temperature photoluminescence was further carried out on the indium oxide samples to investigate their optical properties.

Nanotechnology, 2009

We demonstrate the effect of surface chemical dynamics on carrier transport and recombination pro... more We demonstrate the effect of surface chemical dynamics on carrier transport and recombination processes of electron-hole pairs in ZnO nanowire field effect transistors. We have found that the electrical conductance decreases and the threshold voltages shift in a positive gate voltage direction, as electrical characteristics are measured repeatedly. We associate this with the enhancement of oxygen adsorption by capturing electrons from the induced current during the probing. This results in an overall depletion of electrons and thus causes the positive shift in threshold voltages associated with the origin and width of characteristic hysteresis loops. In addition, the surface environment dependence of the photo-response related to a recombination process in ZnO nanowires is discussed in terms of the surface chemical reaction and band bending.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2006

We demonstrate the fabrication of sub-10-nm high aspect ratio electron beam patterning of ZnO at ... more We demonstrate the fabrication of sub-10-nm high aspect ratio electron beam patterning of ZnO at the center as well as corners of the 500 m square main deflection field using a negative tone zinc naphthenate resist. After electron beam exposure, the resist was developed in toluene, resulting in high-resolution patterns as small as 7 nm with an aspect ratio of ϳ10 in the center as well as at the corners of the main field. The line edge roughness ͑3͒ of these lines shows roughness with fluctuations of about 2.8 nm; thus making it the smallest value of the line edge roughness measured so far for any electron beam resist. Heating the structures at 500°C resulted in reduction of feature sizes to ϳ5 nm and in the formation of crystalline ZnO. Such sub-10-nm high aspect ratio patterning within the main deflection field is an important step to enable full-wafer-level nanofabrication.

IEEE Transactions on Appiled Superconductivity, 2003

We have successfully fabricated high quality Josephson junctions in MgB 2 thin films by a combina... more We have successfully fabricated high quality Josephson junctions in MgB 2 thin films by a combination of 30 kV focused Ga ion beam nanolithography and 50 keV proton ion beam irradiation. The junctions show resistively shunted junction like current-voltage characteristics with additional excess current. Monte Carlo simulation results for the optimized mask structure and experimental results for the dc and ac Josephson effects are presented. This technique is particularly useful for prototyping devices due to its simplicity and flexibility of fabrication and has a great potential for high-density integration.

Journal of Nanoscience and Nanotechnology, 2012

Electrohydrodynamic lithography (EHL) is one of several unusual lithographic techniques for fabri... more Electrohydrodynamic lithography (EHL) is one of several unusual lithographic techniques for fabricating sub-micrometer structures over a large area. EHL uses the electrohydrodynamic (EHD) film instability induced by a laterally modulated electric field, which allows it to fabricate not only general organic structures but also structures of various components, such as diblock copolymers and inorganic materials, without contact between the resist and the stamp. Furthermore, EHL is a very special lithographic technique in that diverse structures are fabricated from one stamp via electric field modulation. The electric field is controlled by the replication time, air layer thickness, etc. A replicated inorganic structure was demonstrated from a hexagonal hole and line arrays. The heat treatment of the replicated pattern was carried out to obtain the crystalline phase, after which the samples were characterized via Raman spectroscopy. These values were ascertained using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The results will be useful in providing a facile route for patterning functional metal oxides over a large area. Such a technique can be used to produce photovoltaic cells, memory devices, display devices, etc.

Chemical Communications, 2010

Single crystalline MoO(3) and Cu(0.33)MoO(3) nanorods have been synthesized in large quantities v... more Single crystalline MoO(3) and Cu(0.33)MoO(3) nanorods have been synthesized in large quantities via hydrothermal route, which exhibit unprecedented photocatalytic performance for the decomposition of Toluidine blue "O" (TBO) and chlorobenzene both under visible and UV light irradiation.

Journal of the American Chemical Society, 2008

Recently, because of the record-high oil prices and the serious global warming problems, the deve... more Recently, because of the record-high oil prices and the serious global warming problems, the development of hybrid electric vehicles (HEVs) is under the spotlight and lithium ion batteries (LIBs) have been a strong candidate for powering them. One of the key safety issues in LIBs for HEVs would be the dendritic lithium growth on the anode surface at high charging current because the conventional carbonous materials approach almost 0 V vs Li at the end of Li insertion. 1 Therefore, a fundamental solution is to use an electrochemical redox couple with higher equilibrium potentials, which makes Li formation thermodynamically less favorable. Among the candidates, Li 4 Ti 5 O 12 using the Ti 4+ /Ti 3+ redox couple (ca. 1.5 V vs Li) has showed promising electrochemical properties with structural and chemical stabilities vis-à-vis to the electrolyte. 2 The electronic structure of Li 4 Ti 5 O 12 characterized by empty Ti 3d-states with a band gap energy of ∼2 eV gives an insulating character to this material. 3 Therefore, the high current properties of Li 4 Ti 5 O 12 might not be sufficient for high current applications before any materials modifications.