Three types of self-assembled monolayers (SAMs) are employed for the investigation of protein adsorption. An octadecylsilane (ODS) SAM, a fluoroalkylsilane (FAS) SAM, and a polyethylene glycol (PEG) SAM are selected as examples. The amount of adsorbed protein is measured by fluorescent microscopy. A molecular dynamics (MD) simulation is carried out for modeling both the molecular structures of the SAMs and the water structure on the SAMs. A hydrophilic PEG SAM prevents protein adsorption, while a large amount of adsorption is observed on a hydrophobic ODS SAM. In spite of the hydrophobicity, an FAS SAM prevents protein adsorption as well as a PEG SAM. MD calculation suggests that the existence of surface-bound water on an ODS SAM induces protein, adsorption. In the case of the FAS SAM, owing to the electrostatic interaction and the flexibility of the precursor, the water molecule is not bound to the surface and protein adsorption is suppressed.

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900 degrees C/15 min, (B) 850 degrees C/1 h, and (C) 850 degrees C/1 h with a subsequent 1000 degrees C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that g(m) enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900 degrees C/15 min, (B) 850 degrees C/1 h, and (C) 850 degrees C/1 h with a subsequent 1000 degrees C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that g(m) enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900 degrees C/15 min, (B) 850 degrees C/1 h, and (C) 850 degrees C/1 h with a subsequent 1000 degrees C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that g(m) enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900 degrees C/15 min, (B) 850 degrees C/1 h, and (C) 850 degrees C/1 h with a subsequent 1000 degrees C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that g(m) enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.

An ultrasensitive and facile bioassay approach is developed using biofunctional multi-walled carbon nanotubes (MWNTs). The biofunctional MWNTs are exploited to detect trace protein in the homogeneous solution using fluorescent detection. The effect of target concentration on the fluorescent intensity is systematically studied, revealing that the detected signal is strengthened with increase in target concentration. The homogenous target-capture process performed on the biofunctional MWNTs enhances the detection sensitivity largely. The detection limit of 100 pg/ml is achieved through this bioassay. (c) 2007 Elsevier B.V. All rights reserved.

An ultrasensitive and facile bioassay approach is developed using biofunctional multi-walled carbon nanotubes (MWNTs). The biofunctional MWNTs are exploited to detect trace protein in the homogeneous solution using fluorescent detection. The effect of target concentration on the fluorescent intensity is systematically studied, revealing that the detected signal is strengthened with increase in target concentration. The homogenous target-capture process performed on the biofunctional MWNTs enhances the detection sensitivity largely. The detection limit of 100 pg/ml is achieved through this bioassay. (c) 2007 Elsevier B.V. All rights reserved.

The combination of electron beam lithography and gold nanoparticle-based detection method is subject to a novel high-resolution approach to detecting DNA nanoarrays. In this work, gold nanoparticle-based detection of DNA hybridization on nanostructured arrays is presented. The nanostructured arrays were created by electron beam lithography of a self-assembled monolayer. Amine groups, which are active moieties and are used for attachment of DNA, were introduced to the nanostructures, and the amine-modified structures were characterized by scanning Maxwell-stress microscopy (SMM) for seeing the modification process. The DNA probe covalently immobilized within the nanostructures was hybridized with a biotinylated target DNA. Streptavidin-gold conjugate was then bound to the biotin, thereby assembling inside the nanostructured arrays. The sequence-specific hybridization was imaged by atomic force microscopy (AFM). On the other hand, the activity of the DNA molecules within the nanostructured arrays was verified by fluorescence microscopy using streptavidin-Cy 5 conjugate instead of streptavidin-gold nanoparticles conjugate. On the basis of fluorescent detection, an alternative method has been developed for detection of DNA nanostructures, which will benefit the development of DNA chips.

We have performed three-dimensional molecular dynamics simulations to investigate strain and stress distributions in silicon nanostructures covered with thermal oxide films, by using our original molecular force field for Si, O mixed systems. We have modeled a wire-shaped nanostructure by carving a Si(001) substrate, and then an oxide film with a uniform thickness was formed by inserting oxygen atom into Si-Si bonds from the surface. The simulation results show that a compressive stress is concentrated on the oxide region in the vicinity of the side SiO2/Si interface of the nanowire. At the top interface, there is also a compressive stress in the [110] direction, whereas the [001] component of the normal stress tensor is almost relaxed. These results suggest that the oxidation is strongly suppressed at the side faces of the silicon nanowire.

The binding energies between luciferin and luciferase adsorbed on a Si surface were estimated by docking simulations. These binding energies were more stable on a hydrophilic Si surface than on a hydrophobic Si surface, but their difference was small. Luciferase adsorbed more strongly on the hydrophobic Si surface than on the hydrophilic Si surface. The luciferase active site was not covered by the Si surface in this adsorption state. The hydrophobic surface would be suitable for the immobilization of luciferase both from the viewpoints of the binding of luciferin to luciferase and the adsorption of luciferase to the Si surface. (C) 2007 Elsevier B.V. All rights reserved.

The combination of electron beam lithography and gold nanoparticle-based detection method is subject to a novel high-resolution approach to detecting DNA nanoarrays. In this work, gold nanoparticle-based detection of DNA hybridization on nanostructured arrays is presented. The nanostructured arrays were created by electron beam lithography of a self-assembled monolayer. Amine groups, which are active moieties and are used for attachment of DNA, were introduced to the nanostructures, and the amine-modified structures were characterized by scanning Maxwell-stress microscopy (SMM) for seeing the modification process. The DNA probe covalently immobilized within the nanostructures was hybridized with a biotinylated target DNA. Streptavidin-gold conjugate was then bound to the biotin, thereby assembling inside the nanostructured arrays. The sequence-specific hybridization was imaged by atomic force microscopy (AFM). On the other hand, the activity of the DNA molecules within the nanostructured arrays was verified by fluorescence microscopy using streptavidin-Cy 5 conjugate instead of streptavidin-gold nanoparticles conjugate. On the basis of fluorescent detection, an alternative method has been developed for detection of DNA nanostructures, which will benefit the development of DNA chips.

We have performed three-dimensional molecular dynamics simulations to investigate strain and stress distributions in silicon nanostructures covered with thermal oxide films, by using our original molecular force field for Si, O mixed systems. We have modeled a wire-shaped nanostructure by carving a Si(001) substrate, and then an oxide film with a uniform thickness was formed by inserting oxygen atom into Si-Si bonds from the surface. The simulation results show that a compressive stress is concentrated on the oxide region in the vicinity of the side SiO2/Si interface of the nanowire. At the top interface, there is also a compressive stress in the [110] direction, whereas the [001] component of the normal stress tensor is almost relaxed. These results suggest that the oxidation is strongly suppressed at the side faces of the silicon nanowire.

The binding energies between luciferin and luciferase adsorbed on a Si surface were estimated by docking simulations. These binding energies were more stable on a hydrophilic Si surface than on a hydrophobic Si surface, but their difference was small. Luciferase adsorbed more strongly on the hydrophobic Si surface than on the hydrophilic Si surface. The luciferase active site was not covered by the Si surface in this adsorption state. The hydrophobic surface would be suitable for the immobilization of luciferase both from the viewpoints of the binding of luciferin to luciferase and the adsorption of luciferase to the Si surface. (C) 2007 Elsevier B.V. All rights reserved.

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-IgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity.

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-lgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity. Copyright © 2007 American Scientific Publishers All rights reserved.

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-IgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity.

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-IgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity.

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-IgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity.

A formulated kinetic theory for thermal oxidation of silicon is presented in detail. The theory does not involve the rate-limiting step of the interfacial oxidation reaction, instead it is supposed that the diffusivity is suppressed in a strained oxide region near the SiO2/Si interface. The expression of the parabolic constant is the same as that of the Deal - Grove model, while the linear constant makes a clear distinction with the model. The estimated thickness using the expression is close to 1 nm, which compares well with the thickness of the structural transition layer. The origin of the deviation from the linear-parabolic relationship observed at initial oxidation stages can be explained by the enhanced diffusion hypothesis, which is the opposite conclusion to the Deal - Grove theory. (c) 2007 The Electrochemical Society.

A newly formulated kinetic theory for thermal oxidation of silicon is reviewed. The new theory does not involve the rate-limiting step of the interfacial oxidation reaction, instead it is supposed that the diffusivity is suppressed in a strained oxide region near the SiO2/Si interface. The expression of the parabolic constant is the same as that of the Deal-Grove model, while the linear constant makes a clear distinction with the model. The estimated thickness using the new expression is close to 1 nm, which compares well with the thickness of the structural transition layer. The origin of the deviation from the linear-parabolic relationship observed at initial oxidation stages can be explained by the enhanced diffusion hypothesis, which is opposite conclusion to the Deal-Grove theory. © The Electrochemical Society.

A formulated kinetic theory for thermal oxidation of silicon is presented in detail. The theory does not involve the rate-limiting step of the interfacial oxidation reaction, instead it is supposed that the diffusivity is suppressed in a strained oxide region near the Si O2 Si interface. The expression of the parabolic constant is the same as that of the Deal-Grove model, while the linear constant makes a clear distinction with the model. The estimated thickness using the expression is close to 1 nm, which compares well with the thickness of the structural transition layer. The origin of the deviation from the linear-parabolic relationship observed at initial oxidation stages can be explained by the enhanced diffusion hypothesis, which is the opposite conclusion to the Deal-Grove theory. © 2007 The Electrochemical Society.

The feasibility of using an octenyltrimethoxysilane (OCS) self-assembled monolayer (SAM) as a high-resolution electron beam (EB) resist is investigated. The vinyl groups of the OCS SAM can be modified into hydroxy groups, which are useful for biochip fabrication. The hydroxy-modified OCS SAM exhibits higher sensitivity than a vinyl-terminated one. By using the hydroxy-modified OCS SAM as an EB resist, a miniaturized pattern of 18 nm is achieved. Since the hydroxy-modified OCS SAM is repellent to many proteins, this methodology can be useful for the fabrication of protein-immobilizing templates of a molecular scale. (c) 2006 Elsevier B.V. All rights reserved.

The feasibility of using an octenyltrimethoxysilane (OCS) self-assembled monolayer (SAM) as a high-resolution electron beam (EB) resist is investigated. The vinyl groups of the OCS SAM can be modified into hydroxy groups, which are useful for biochip fabrication. The hydroxy-modified OCS SAM exhibits higher sensitivity than a vinyl-terminated one. By using the hydroxy-modified OCS SAM as an EB resist, a miniaturized pattern of 18 nm is achieved. Since the hydroxy-modified OCS SAM is repellent to many proteins, this methodology can be useful for the fabrication of protein-immobilizing templates of a molecular scale. (c) 2006 Elsevier B.V. All rights reserved.

The feasibility of using an octenyltrimethoxysilane (OCS) self-assembled monolayer (SAM) as a high-resolution electron beam (EB) resist is investigated. The vinyl groups of the OCS SAM can be modified into hydroxy groups, which are useful for biochip fabrication. The hydroxy-modified OCS SAM exhibits higher sensitivity than a vinyl-terminated one. By using the hydroxy-modified OCS SAM as an EB resist, a miniaturized pattern of 18 nm is achieved. Since the hydroxy-modified OCS SAM is repellent to many proteins, this methodology can be useful for the fabrication of protein-immobilizing templates of a molecular scale. (c) 2006 Elsevier B.V. All rights reserved.

The packing of submicrometer-sized polystyrene particles within the micrometer-sized recessed patterns were achieved using silicon-microfabricated substrates and a simple dipping and pulling-up process. The polystyrene particles were selectively deposited within the micrometer-sized square, triangular, or circular recessed patterns by tuning the experimental conditions during the pulling-up process. The process produced a capillary force, i.e., a gas-liquid interfacial tension, to push the particles into the recessed patterns on the substrate. In most cases, the selectively depositing particles within the recessed patterns self-organically formed the closest packing structures. However, a special phenomenon, cubic packing structures of the particles, was observed when using square patterns with a few times larger side-length than the particle diameters. Several particle packing structures within different-sized square patterns were demonstrated, and the relationship between the particle packing structures and square pattern sizes were discussed. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

The packing of submicrometer-sized polystyrene particles within the micrometer-sized recessed patterns were achieved using silicon-microfabricated substrates and a simple dipping and pulling-up process. The polystyrene particles were selectively deposited within the micrometer-sized square, triangular, or circular recessed patterns by tuning the experimental conditions during the pulling-up process. The process produced a capillary force, i.e., a gas-liquid interfacial tension, to push the particles into the recessed patterns on the substrate. In most cases, the selectively depositing particles within the recessed patterns self-organically formed the closest packing structures. However, a special phenomenon, cubic packing structures of the particles, was observed when using square patterns with a few times larger side-length than the particle diameters. Several particle packing structures within different-sized square patterns were demonstrated, and the relationship between the particle packing structures and square pattern sizes were discussed. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

The packing of submicrometer-sized polystyrene particles within the micrometer-sized recessed patterns were achieved using silicon-microfabricated substrates and a simple dipping and pulling-up process. The polystyrene particles were selectively deposited within the micrometer-sized square, triangular, or circular recessed patterns by tuning the experimental conditions during the pulling-up process. The process produced a capillary force, i.e., a gas-liquid interfacial tension, to push the particles into the recessed patterns on the substrate. In most cases, the selectively depositing particles within the recessed patterns self-organically formed the closest packing structures. However, a special phenomenon, cubic packing structures of the particles, was observed when using square patterns with a few times larger side-length than the particle diameters. Several particle packing structures within different-sized square patterns were demonstrated, and the relationship between the particle packing structures and square pattern sizes were discussed. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

We report a novel method of one-step direct amination oil polycrystalline diamond to produce functionalized surfaces for DNA micropatterning by photolithography. Polycrystalline diamond was exposed to UV irradiation in ammonia gas to generate amine groups directly. After patterning, optical microscopy confirmed that micropatterns covered with an Au mask were regular in size and shape. The regions outside the micropatterns were passivated with fluorine termination by C3F8 plasma, and the chemical changes on the two different surfaces-the amine groups inside the patterned regions by one-step direct amination and fluorine termination outside the patterned regions-were characterized by spatially resolved X-ray photoelectron spectroscopy (XPS). The patterned areas terminated with active amine groups were then immobilized with probe DNA via a bifunctional molecule. The sequence specificity was conducted by hybridizing fluorescently labeled target DNA to both complementary and noncomplementary probe DNA attached inside the micropatterns. The fluorescence micropatterns observed by epifluorescence microscopy corresponded to those imaged by optical microscopy. DNA hybridization and denaturation experiments on a DNA-modified diamond show that the diamond surfaces reveal superior stability. The influence of a different amination time oil fluorescence intensity was compared. Different terminations as passivated layers were investigated, and as a result, fluorine termination points to the greatest signal-to-noise ratio.

We report a novel method of one-step direct amination oil polycrystalline diamond to produce functionalized surfaces for DNA micropatterning by photolithography. Polycrystalline diamond was exposed to UV irradiation in ammonia gas to generate amine groups directly. After patterning, optical microscopy confirmed that micropatterns covered with an Au mask were regular in size and shape. The regions outside the micropatterns were passivated with fluorine termination by C3F8 plasma, and the chemical changes on the two different surfaces-the amine groups inside the patterned regions by one-step direct amination and fluorine termination outside the patterned regions-were characterized by spatially resolved X-ray photoelectron spectroscopy (XPS). The patterned areas terminated with active amine groups were then immobilized with probe DNA via a bifunctional molecule. The sequence specificity was conducted by hybridizing fluorescently labeled target DNA to both complementary and noncomplementary probe DNA attached inside the micropatterns. The fluorescence micropatterns observed by epifluorescence microscopy corresponded to those imaged by optical microscopy. DNA hybridization and denaturation experiments on a DNA-modified diamond show that the diamond surfaces reveal superior stability. The influence of a different amination time oil fluorescence intensity was compared. Different terminations as passivated layers were investigated, and as a result, fluorine termination points to the greatest signal-to-noise ratio.

We report a novel method of one-step direct amination oil polycrystalline diamond to produce functionalized surfaces for DNA micropatterning by photolithography. Polycrystalline diamond was exposed to UV irradiation in ammonia gas to generate amine groups directly. After patterning, optical microscopy confirmed that micropatterns covered with an Au mask were regular in size and shape. The regions outside the micropatterns were passivated with fluorine termination by C3F8 plasma, and the chemical changes on the two different surfaces-the amine groups inside the patterned regions by one-step direct amination and fluorine termination outside the patterned regions-were characterized by spatially resolved X-ray photoelectron spectroscopy (XPS). The patterned areas terminated with active amine groups were then immobilized with probe DNA via a bifunctional molecule. The sequence specificity was conducted by hybridizing fluorescently labeled target DNA to both complementary and noncomplementary probe DNA attached inside the micropatterns. The fluorescence micropatterns observed by epifluorescence microscopy corresponded to those imaged by optical microscopy. DNA hybridization and denaturation experiments on a DNA-modified diamond show that the diamond surfaces reveal superior stability. The influence of a different amination time oil fluorescence intensity was compared. Different terminations as passivated layers were investigated, and as a result, fluorine termination points to the greatest signal-to-noise ratio.

Molecular mechanics (MM) and molecular dynamics (MID) simulations have been performed to investigate the two-dimensional structure of organosilane self-assembled monolavers (SAMs). Unlike alkanethiol SAMs, the arrangement of molecules in organosilane SAMs is not crystalline, and their molecular structure yet remains undetermined. AMBER 8 is employed with our newly developed Si parameters for the MM/MD simulations. Simulations performed for structures with different bonding networks in the polysiloxane layer shows that the ratio of hydrogen bonds has a profound effect on conformations and strain energies of optimized structures. Our results suggest that alkylsilane SAMs formed on substrates are not perfectly uniform but may have some defects.

Molecular mechanics (MM) and molecular dynamics (MID) simulations have been performed to investigate the two-dimensional structure of organosilane self-assembled monolavers (SAMs). Unlike alkanethiol SAMs, the arrangement of molecules in organosilane SAMs is not crystalline, and their molecular structure yet remains undetermined. AMBER 8 is employed with our newly developed Si parameters for the MM/MD simulations. Simulations performed for structures with different bonding networks in the polysiloxane layer shows that the ratio of hydrogen bonds has a profound effect on conformations and strain energies of optimized structures. Our results suggest that alkylsilane SAMs formed on substrates are not perfectly uniform but may have some defects.

Molecular mechanics (MM) and molecular dynamics (MID) simulations have been performed to investigate the two-dimensional structure of organosilane self-assembled monolavers (SAMs). Unlike alkanethiol SAMs, the arrangement of molecules in organosilane SAMs is not crystalline, and their molecular structure yet remains undetermined. AMBER 8 is employed with our newly developed Si parameters for the MM/MD simulations. Simulations performed for structures with different bonding networks in the polysiloxane layer shows that the ratio of hydrogen bonds has a profound effect on conformations and strain energies of optimized structures. Our results suggest that alkylsilane SAMs formed on substrates are not perfectly uniform but may have some defects.

We present a simple method for improving the field emission performance of tungsten-tip electron sources based on single-walled carbon nanotube (SWCNT) modification. By coating a sandwich-like thin film of Al-Fe-Al (with Fe as a catalyst) on a tungsten tip, SWCNTs were synthesized at 600 degrees C in a chemical vapor deposition (CVD) reactor. The influence of CNT modification on the electron emission characteristics of the emitters was investigated by means of a triode structure. We have found that CNT-modified tungsten tips exhibit low threshold-voltage for electron emission, and improved emission-current stability, compared with nonmodified and Al-Fe-Al-coated needles. (c) 2006 American Institute of Physics.

We have performed a series of molecular dynamics (MD) simulations on interactions between green fluorescent protein (GFP) and Si substrates. The results show that GFP adsorbs directly on the hydrophobic substrate, and via water molecules on the hydrophilic substrate. The adsorption-induced changes in the conformation of GFP are smaller on the hydrophilic substrate than on the hydrophobic substrate. On the other hand, the dynamic atom motions in GFP are larger on the hydrophobic substrate than on the hydrophilic substrate. In order to prevent the denaturation of proteins caused by immobilization on a substrate, the Si surface should be prepared from the viewpoints of both conformation and dynamic atom motions.

As the size of semiconductor devices continues to shrink, the normally random distribution of the individual dopant atoms within the semiconductor becomes a critical factor in determining device performance-homogeneity can no longer be assumed(1-5). Here we report the fabrication of semiconductor devices in which both the number and position of the dopant atoms are precisely controlled. To achieve this, we make use of a recently developed single-ion implantation technique(6-9), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the desired number is reached. Electrical measurements of the resulting transistors reveal that device-to-device fluctuations in the threshold voltage (V-th; the turn-on voltage of the device) are less for those structures with ordered dopant arrays than for those with conventional random doping. We also find that the devices with ordered dopant arrays exhibit a shift in V-th, relative to the undoped semiconductor, that is twice that for a random dopant distribution (-0.4 V versus -0.2 V); we attribute this to the uniformity of electrostatic potential in the conducting channel region due to the ordered distribution of dopant atoms. Our results therefore serve to highlight the improvements in device performance that can be achieved through atomic-scale control of the doping process. Furthermore, ordered dopant arrays of this type may enhance the prospects for realizing silicon-based solid-state quantum computers(10).

As the size of semiconductor devices continues to shrink, the normally random distribution of the individual dopant atoms within the semiconductor becomes a critical factor in determining device performance-homogeneity can no longer be assumed(1-5). Here we report the fabrication of semiconductor devices in which both the number and position of the dopant atoms are precisely controlled. To achieve this, we make use of a recently developed single-ion implantation technique(6-9), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the desired number is reached. Electrical measurements of the resulting transistors reveal that device-to-device fluctuations in the threshold voltage (V-th; the turn-on voltage of the device) are less for those structures with ordered dopant arrays than for those with conventional random doping. We also find that the devices with ordered dopant arrays exhibit a shift in V-th, relative to the undoped semiconductor, that is twice that for a random dopant distribution (-0.4 V versus -0.2 V); we attribute this to the uniformity of electrostatic potential in the conducting channel region due to the ordered distribution of dopant atoms. Our results therefore serve to highlight the improvements in device performance that can be achieved through atomic-scale control of the doping process. Furthermore, ordered dopant arrays of this type may enhance the prospects for realizing silicon-based solid-state quantum computers(10).

As the size of semiconductor devices continues to shrink, the normally random distribution of the individual dopant atoms within the semiconductor becomes a critical factor in determining device performance-homogeneity can no longer be assumed(1-5). Here we report the fabrication of semiconductor devices in which both the number and position of the dopant atoms are precisely controlled. To achieve this, we make use of a recently developed single-ion implantation technique(6-9), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the desired number is reached. Electrical measurements of the resulting transistors reveal that device-to-device fluctuations in the threshold voltage (V-th; the turn-on voltage of the device) are less for those structures with ordered dopant arrays than for those with conventional random doping. We also find that the devices with ordered dopant arrays exhibit a shift in V-th, relative to the undoped semiconductor, that is twice that for a random dopant distribution (-0.4 V versus -0.2 V); we attribute this to the uniformity of electrostatic potential in the conducting channel region due to the ordered distribution of dopant atoms. Our results therefore serve to highlight the improvements in device performance that can be achieved through atomic-scale control of the doping process. Furthermore, ordered dopant arrays of this type may enhance the prospects for realizing silicon-based solid-state quantum computers(10).

To address the reactions and diffusion of atomic and molecular oxygen in SiO2, the modification of the SiO2 network on exposure to an atomic or molecular oxygen atmosphere is investigated by measuring the x-ray-diffraction profile of the residual order peak emanating from the oxide. Analyses of the peak intensity and its fringe pattern provide experimental evidence for the recent theoretical predictions, indicating that atomic oxygen is incorporated into the SiO2 network near the surface and diffuses toward the interface along with modifying it even at a low temperature of 400 degrees C, whereas molecular oxygen diffuses without reacting with the bulk SiO2 even at a temperature of 850 degrees C that is sufficiently high for oxidation reaction at the interface.

We propose a novel process for preferential immobilization of deoxyribonucleic acid (DNA) and green fluorescent protein (GFP) onto organosilane self-assembled monolayer (SAM) templates. One of the advantages of using the organosilane SAM as the template is that it is electron-beam sensitive and, by utilizing the SAM as an alternative resist film, we can make nanopatterns on a molecular scale because the proximity effect is negligible owing to the film's thinness. An other advantage is that the organosilane SAM is repellent to both DNA and GFP. Thus, the patterned SAM can be utilized as the passivation film covering the outside of the pattern while DNA and GFP are immobilized within the pattern. We investigate two kinds of organosilane SAMs for the template. One is n-octadecyltrimethoxysilane (ODS) SAM, and the other is 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDS) SAM. Our results indicate that the ODS SAM is more repellent to DNA than the FDS SAM and is suitable for DNA immobilization, while the FDS SAM template is suitable for GFP immobilization via biotin-avidin coupling because the FDS SAM surface prevents the nonspecific adsorption of streptavidin. Although the nonspecific adsorption of DNA and GFP on a SAM is also recognized, by controlling both the concentration and the incubation time, we can immobilize DNA and GFP preferentially onto nanopatterns of 100 nm diameter.

A novel process for the fabrication of a gated silicon field emitter array is proposed. The process involves complete self-alignment of gate electrodes taking advantage of ion bombardment retarded etching. The ion-irradiated regions serve as masks for subsequent silicon etching resulting in the formation of tabletop structures. The structures are suitable for both the formation of pyramidal emitters and the arrangement of gate electrodes adjacent to each emitter. We integrate this silicon etching into a self-align process for the fabrication of gated emitter array. The emission characteristics of 100 emitters are tested, and the emission at a gate voltage of 30 V is detected. The results indicate that the proposed process is applicable to the fabrication of gated silicon emitters.

We propose a novel process for preferential immobilization of deoxyribonucleic acid (DNA) and green fluorescent protein (GFP) onto organosilane self-assembled monolayer (SAM) templates. One of the advantages of using the organosilane SAM as the template is that it is electron-beam sensitive and, by utilizing the SAM as an alternative resist film, we can make nanopatterns on a molecular scale because the proximity effect is negligible owing to the film's thinness. An other advantage is that the organosilane SAM is repellent to both DNA and GFP. Thus, the patterned SAM can be utilized as the passivation film covering the outside of the pattern while DNA and GFP are immobilized within the pattern. We investigate two kinds of organosilane SAMs for the template. One is n-octadecyltrimethoxysilane (ODS) SAM, and the other is 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDS) SAM. Our results indicate that the ODS SAM is more repellent to DNA than the FDS SAM and is suitable for DNA immobilization, while the FDS SAM template is suitable for GFP immobilization via biotin-avidin coupling because the FDS SAM surface prevents the nonspecific adsorption of streptavidin. Although the nonspecific adsorption of DNA and GFP on a SAM is also recognized, by controlling both the concentration and the incubation time, we can immobilize DNA and GFP preferentially onto nanopatterns of 100 nm diameter.

A novel process for the fabrication of a gated silicon field emitter array is proposed. The process involves complete self-alignment of gate electrodes taking advantage of ion bombardment retarded etching. The ion-irradiated regions serve as masks for subsequent silicon etching resulting in the formation of tabletop structures. The structures are suitable for both the formation of pyramidal emitters and the arrangement of gate electrodes adjacent to each emitter. We integrate this silicon etching into a self-align process for the fabrication of gated emitter array. The emission characteristics of 100 emitters are tested, and the emission at a gate voltage of 30 V is detected. The results indicate that the proposed process is applicable to the fabrication of gated silicon emitters.

To address the reactions and diffusion of atomic and molecular oxygen in SiO2, the modification of the SiO2 network on exposure to an atomic or molecular oxygen atmosphere is investigated by measuring the x-ray-diffraction profile of the residual order peak emanating from the oxide. Analyses of the peak intensity and its fringe pattern provide experimental evidence for the recent theoretical predictions, indicating that atomic oxygen is incorporated into the SiO2 network near the surface and diffuses toward the interface along with modifying it even at a low temperature of 400 degrees C, whereas molecular oxygen diffuses without reacting with the bulk SiO2 even at a temperature of 850 degrees C that is sufficiently high for oxidation reaction at the interface.

We propose a novel process for preferential immobilization of deoxyribonucleic acid (DNA) and green fluorescent protein (GFP) onto organosilane self-assembled monolayer (SAM) templates. One of the advantages of using the organosilane SAM as the template is that it is electron-beam sensitive and, by utilizing the SAM as an alternative resist film, we can make nanopatterns on a molecular scale because the proximity effect is negligible owing to the film's thinness. An other advantage is that the organosilane SAM is repellent to both DNA and GFP. Thus, the patterned SAM can be utilized as the passivation film covering the outside of the pattern while DNA and GFP are immobilized within the pattern. We investigate two kinds of organosilane SAMs for the template. One is n-octadecyltrimethoxysilane (ODS) SAM, and the other is 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDS) SAM. Our results indicate that the ODS SAM is more repellent to DNA than the FDS SAM and is suitable for DNA immobilization, while the FDS SAM template is suitable for GFP immobilization via biotin-avidin coupling because the FDS SAM surface prevents the nonspecific adsorption of streptavidin. Although the nonspecific adsorption of DNA and GFP on a SAM is also recognized, by controlling both the concentration and the incubation time, we can immobilize DNA and GFP preferentially onto nanopatterns of 100 nm diameter.

A novel process for the fabrication of a gated silicon field emitter array is proposed. The process involves complete self-alignment of gate electrodes taking advantage of ion bombardment retarded etching. The ion-irradiated regions serve as masks for subsequent silicon etching resulting in the formation of tabletop structures. The structures are suitable for both the formation of pyramidal emitters and the arrangement of gate electrodes adjacent to each emitter. We integrate this silicon etching into a self-align process for the fabrication of gated emitter array. The emission characteristics of 100 emitters are tested, and the emission at a gate voltage of 30 V is detected. The results indicate that the proposed process is applicable to the fabrication of gated silicon emitters.

A novel point-arc microwave plasma chemical vapor deposition (CVD) apparatus was employed to grow single-walled carbon nanotubes (SWNTs) on Si substrates coated with a sandwich-like nano-layer structure of 0.7 nm Al2O3 (top)/0.5 nm Fe/ 5-70nm Al2O3 by conventional high frequency sputtering. The growth of extremely dense and vertically aligned SWNTs with an almost constant growth rate of 270 mu m/h within 40 min at a temperature as low as 600 degrees C was demonstrated for the first time. The volume density of the as-grown SWNT films is as higher as 66 kg/m(3).

A novel point-arc microwave plasma chemical vapor deposition (CVD) apparatus was employed to grow single-walled carbon nanotubes (SWNTs) on Si substrates coated with a sandwich-like nano-layer structure of 0.7 nm Al2O3 (top)/0.5 nm Fe/ 5-70nm Al2O3 by conventional high frequency sputtering. The growth of extremely dense and vertically aligned SWNTs with an almost constant growth rate of 270 mu m/h within 40 min at a temperature as low as 600 degrees C was demonstrated for the first time. The volume density of the as-grown SWNT films is as higher as 66 kg/m(3).

A novel point-arc microwave plasma chemical vapor deposition (CVD) apparatus was employed to grow single-walled carbon nanotubes (SWNTs) on Si substrates coated with a sandwich-like nano-layer structure of 0.7 nm Al2O3 (top)/0.5 nm Fe/ 5-70nm Al2O3 by conventional high frequency sputtering. The growth of extremely dense and vertically aligned SWNTs with an almost constant growth rate of 270 mu m/h within 40 min at a temperature as low as 600 degrees C was demonstrated for the first time. The volume density of the as-grown SWNT films is as higher as 66 kg/m(3).

DNA micropatterns have been for the first time fabricated on a single-crystal diamond surface in conjunction with the photolithography technique. A new chemical modification process for producing amine groups inside patterned regions and a passivation layer terminated with fluorine outside patterned regions is demonstrated. The resulting amine groups within patterned areas and fluorine termination outside patterned areas on the single-crystal diamond surface were characterized by spatially resolved X-ray photoelectron spectroscopy. Amine-terminated oligonucleotides were then linked to the amine patterned regions using a crosslinker. It was revealed that hybridization on DNA-patterned diamond is specific and selective, with a low background outside the patterns and strong binding to complementary probe DNA immobilized inside the patterns but no binding to noncomplementary probe DNA similarly immobilized inside the patterns. These results suggest that DNA micropatteming on a single-crystal diamond may serve as an ideal platform for future biochips and biosensors.

DNA micropatterns have been for the first time fabricated on a single-crystal diamond surface in conjunction with the photolithography technique. A new chemical modification process for producing amine groups inside patterned regions and a passivation layer terminated with fluorine outside patterned regions is demonstrated. The resulting amine groups within patterned areas and fluorine termination outside patterned areas on the single-crystal diamond surface were characterized by spatially resolved X-ray photoelectron spectroscopy. Amine-terminated oligonucleotides were then linked to the amine patterned regions using a crosslinker. It was revealed that hybridization on DNA-patterned diamond is specific and selective, with a low background outside the patterns and strong binding to complementary probe DNA immobilized inside the patterns but no binding to noncomplementary probe DNA similarly immobilized inside the patterns. These results suggest that DNA micropatteming on a single-crystal diamond may serve as an ideal platform for future biochips and biosensors.

DNA micropatterns have been for the first time fabricated on a single-crystal diamond surface in conjunction with the photolithography technique. A new chemical modification process for producing amine groups inside patterned regions and a passivation layer terminated with fluorine outside patterned regions is demonstrated. The resulting amine groups within patterned areas and fluorine termination outside patterned areas on the single-crystal diamond surface were characterized by spatially resolved X-ray photoelectron spectroscopy. Amine-terminated oligonucleotides were then linked to the amine patterned regions using a crosslinker. It was revealed that hybridization on DNA-patterned diamond is specific and selective, with a low background outside the patterns and strong binding to complementary probe DNA immobilized inside the patterns but no binding to noncomplementary probe DNA similarly immobilized inside the patterns. These results suggest that DNA micropatteming on a single-crystal diamond may serve as an ideal platform for future biochips and biosensors.

We investigated the atomic structure of the SiO(2)/Si interface and the initial oxidation process of Si surfaces using our developed large-scale atomistic simulation technique for Si, O mixed systems. We constructed large-scale SiO(2)/Si(0 0 1) interface models (now up to 12,536 atoms in size) by inserting O atoms into Si-Si bonds in crystalline Si substrates from the surface of the models. The resulting SiO(2)/Si Models exhibited a compressively strained oxide region near the interface, and reproduced X-ray diffraction peaks compatible with experimental results. Using the large-scale modeling technique, we simulated an atomistic oxidation process where the O atoms were introduced into the Si substrate in one by one so as to minimize the strain energy caused by the insertion of the O atoms. A mostly abrupt change in the composition at the SiO(2)/Si interface was reproduced in this energetic scheme, though the oxidation did not proceed layer by layer as previously reported by many other reports. We found out that the layer-by-layer oxidation phenomenon can be explained by the kinetics of oxidants arriving at the interface through the oxide film. (C) 2004 Elsevier B.V. All rights reserved.

We investigated the atomic structure of the SiO(2)/Si interface and the initial oxidation process of Si surfaces using our developed large-scale atomistic simulation technique for Si, O mixed systems. We constructed large-scale SiO(2)/Si(0 0 1) interface models (now up to 12,536 atoms in size) by inserting O atoms into Si-Si bonds in crystalline Si substrates from the surface of the models. The resulting SiO(2)/Si Models exhibited a compressively strained oxide region near the interface, and reproduced X-ray diffraction peaks compatible with experimental results. Using the large-scale modeling technique, we simulated an atomistic oxidation process where the O atoms were introduced into the Si substrate in one by one so as to minimize the strain energy caused by the insertion of the O atoms. A mostly abrupt change in the composition at the SiO(2)/Si interface was reproduced in this energetic scheme, though the oxidation did not proceed layer by layer as previously reported by many other reports. We found out that the layer-by-layer oxidation phenomenon can be explained by the kinetics of oxidants arriving at the interface through the oxide film. (C) 2004 Elsevier B.V. All rights reserved.

Carbon nanostructures (CN) have been selectively grown directly onto the top of nickel ion implanted nanopyramid array (Ni NPA) by the plasma enhanced chemical vapor deposition (p-CVD) technique. Firstly, NPA were fabricated by taking advantage of the anisotropic etching characteristics of silicon in hydrazine (N2H4H2O); where the ion implanted area acted as a mask for hydrazine etching. Secondly, carbon nanostructures were grown on Ni NPA by feeding methane/hydrogen (CH4/H-2) mixtures into p-CVD reactor. The change of concentration ratio of methane to hydrogen dramatically affected the growth selectivity of CN. Methane concentrations lower than 20%, promoted the selective growth of CN on the top of Ni NPA. Morphology and chemical nature of grown species were studied by employing scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy, respectively. (C) 2004 Elsevier B.V. All rights reserved.

A novel fabrication process of silicon microstructure array for preferential immobilization of biomolecules is proposed. We perform electron beam lithography on a self-assembled monolayer (SAM), and achieve high-density silicon patterns terminated with both 3-aminopropyltriethoxysilane (APTES) and octadecyltrimethoxysilane (ODS). The amino-terminated surface produces the site-directed covalent immobilization of DNA inside the pattern, while the hydrophobic surface of the ODS-SAM prevents the adsorption. As a result, we have succeeded in immobilizing the DNA within the amino-modified area. By using this methodology, we demonstrate the miniaturization of deoxyribonucleic acid (DNA) chip. After the covalent attachment of the amino-modified oligonucleotides to the microstructures, we hybridize the immobilized DNA with the target DNA labeled with a fluorescent dye. The signals from the DNA chip exhibit the specific binding due to the DNA-DNA interaction. These results show the feasibility of this technique for high-density information storage and biochip miniaturization. (C) 2004 Elsevier B.V. All rights reserved.

We propose an improved formula of a previous interatomic potential for Si, O mixed systems. The new potential is designed so as to more accurately reproduce the structural property of compressively strained SiO2 structures, by reducing unnatural steric hindrance caused by a long-range part of a three-body term. As the results of the improvement, (1) compressive stress in SiO2 film, which was highly overestimated to be 13 GPa by the earlier potential, is reduced to 2.7 GPa, and (2) a spurious peak in Si-O pair correlation function of SiO2 film disappeared. A limitation of the conventional interatomic potentials and its solution are also discussed. (C) 2004 Elsevier B.V. All rights reserved.

We report a result of a feasibility study on the application of an octadecyltrimethoxysilane self-assembled monolayer to a resist film for electron beam lithography. The self-assembled monolayer deposited on a silicon dioxide surface by chemical vapor deposition is resistant to both sulfuric acid and hydrofluoric acid. By immersing the electron-beam-irradiated surface into both acids, we successfully develop microstructural patterns in the self-assembled monolayer. In particular, we show the effectiveness of immersing the substrate into a sulfuric-acid-based solution for the development of the pattern. The relationship between the required dose and the developing time is estimated by measuring the morphology of the developed patterns by atomic force microscopy. The pattern in the self-assembled monolayer can be transferred into both the underlying silicon dioxide layer and the silicon substrate. These results indicate that the organosilane self-assembled monolayer serves as an alternative resist for electron beam lithography.

Carbon nanostructures (CN) have been selectively grown directly onto the top of nickel ion implanted nanopyramid array (Ni NPA) by the plasma enhanced chemical vapor deposition (p-CVD) technique. Firstly, NPA were fabricated by taking advantage of the anisotropic etching characteristics of silicon in hydrazine (N2H4H2O); where the ion implanted area acted as a mask for hydrazine etching. Secondly, carbon nanostructures were grown on Ni NPA by feeding methane/hydrogen (CH4/H-2) mixtures into p-CVD reactor. The change of concentration ratio of methane to hydrogen dramatically affected the growth selectivity of CN. Methane concentrations lower than 20%, promoted the selective growth of CN on the top of Ni NPA. Morphology and chemical nature of grown species were studied by employing scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy, respectively. (C) 2004 Elsevier B.V. All rights reserved.

A novel fabrication process of silicon microstructure array for preferential immobilization of biomolecules is proposed. We perform electron beam lithography on a self-assembled monolayer (SAM), and achieve high-density silicon patterns terminated with both 3-aminopropyltriethoxysilane (APTES) and octadecyltrimethoxysilane (ODS). The amino-terminated surface produces the site-directed covalent immobilization of DNA inside the pattern, while the hydrophobic surface of the ODS-SAM prevents the adsorption. As a result, we have succeeded in immobilizing the DNA within the amino-modified area. By using this methodology, we demonstrate the miniaturization of deoxyribonucleic acid (DNA) chip. After the covalent attachment of the amino-modified oligonucleotides to the microstructures, we hybridize the immobilized DNA with the target DNA labeled with a fluorescent dye. The signals from the DNA chip exhibit the specific binding due to the DNA-DNA interaction. These results show the feasibility of this technique for high-density information storage and biochip miniaturization. (C) 2004 Elsevier B.V. All rights reserved.

We propose an improved formula of a previous interatomic potential for Si, O mixed systems. The new potential is designed so as to more accurately reproduce the structural property of compressively strained SiO2 structures, by reducing unnatural steric hindrance caused by a long-range part of a three-body term. As the results of the improvement, (1) compressive stress in SiO2 film, which was highly overestimated to be 13 GPa by the earlier potential, is reduced to 2.7 GPa, and (2) a spurious peak in Si-O pair correlation function of SiO2 film disappeared. A limitation of the conventional interatomic potentials and its solution are also discussed. (C) 2004 Elsevier B.V. All rights reserved.

We report a result of a feasibility study on the application of an octadecyltrimethoxysilane, self-assembled monolayer to a resist film for electron beam lithography. The self-assembled monolayer deposited on a silicon dioxide surface by chemical vapor deposition is resistant to both sulfuric acid and hydrofluoric acid. By immersing the electron-beam-irradiated surface into both acids, we successfully develop microstructural patterns in the self-assembled monolayer. In particular, we show the effectiveness of immersing the substrate into a sulfuric-acid-based solution for the development of the pattern. The relationship between the required dose and the developing time is estimated by measuring the morphology of the developed patterns by atomic force microscopy. The pattern in the self-assembled monolayer can be transferred into both the underlying silicon dioxide layer and the silicon substrate. These results indicate that the organosilane self-assembled monolayer serves as an alternative resist for electron beam lithography.

Carbon nanostructures (CN) have been selectively grown directly onto the top of nickel ion implanted nanopyramid array (Ni NPA) by the plasma enhanced chemical vapor deposition (p-CVD) technique. Firstly, NPA were fabricated by taking advantage of the anisotropic etching characteristics of silicon in hydrazine (N2H4H2O); where the ion implanted area acted as a mask for hydrazine etching. Secondly, carbon nanostructures were grown on Ni NPA by feeding methane/hydrogen (CH4/H-2) mixtures into p-CVD reactor. The change of concentration ratio of methane to hydrogen dramatically affected the growth selectivity of CN. Methane concentrations lower than 20%, promoted the selective growth of CN on the top of Ni NPA. Morphology and chemical nature of grown species were studied by employing scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy, respectively. (C) 2004 Elsevier B.V. All rights reserved.

A novel fabrication process of silicon microstructure array for preferential immobilization of biomolecules is proposed. We perform electron beam lithography on a self-assembled monolayer (SAM), and achieve high-density silicon patterns terminated with both 3-aminopropyltriethoxysilane (APTES) and octadecyltrimethoxysilane (ODS). The amino-terminated surface produces the site-directed covalent immobilization of DNA inside the pattern, while the hydrophobic surface of the ODS-SAM prevents the adsorption. As a result, we have succeeded in immobilizing the DNA within the amino-modified area. By using this methodology, we demonstrate the miniaturization of deoxyribonucleic acid (DNA) chip. After the covalent attachment of the amino-modified oligonucleotides to the microstructures, we hybridize the immobilized DNA with the target DNA labeled with a fluorescent dye. The signals from the DNA chip exhibit the specific binding due to the DNA-DNA interaction. These results show the feasibility of this technique for high-density information storage and biochip miniaturization. (C) 2004 Elsevier B.V. All rights reserved.

We propose an improved formula of a previous interatomic potential for Si, O mixed systems. The new potential is designed so as to more accurately reproduce the structural property of compressively strained SiO2 structures, by reducing unnatural steric hindrance caused by a long-range part of a three-body term. As the results of the improvement, (1) compressive stress in SiO2 film, which was highly overestimated to be 13 GPa by the earlier potential, is reduced to 2.7 GPa, and (2) a spurious peak in Si-O pair correlation function of SiO2 film disappeared. A limitation of the conventional interatomic potentials and its solution are also discussed. (C) 2004 Elsevier B.V. All rights reserved.

We report a result of a feasibility study on the application of an octadecyltrimethoxysilane, self-assembled monolayer to a resist film for electron beam lithography. The self-assembled monolayer deposited on a silicon dioxide surface by chemical vapor deposition is resistant to both sulfuric acid and hydrofluoric acid. By immersing the electron-beam-irradiated surface into both acids, we successfully develop microstructural patterns in the self-assembled monolayer. In particular, we show the effectiveness of immersing the substrate into a sulfuric-acid-based solution for the development of the pattern. The relationship between the required dose and the developing time is estimated by measuring the morphology of the developed patterns by atomic force microscopy. The pattern in the self-assembled monolayer can be transferred into both the underlying silicon dioxide layer and the silicon substrate. These results indicate that the organosilane self-assembled monolayer serves as an alternative resist for electron beam lithography.

We report a result of a feasibility study on the application of an octadecyltrimethoxysilane, self-assembled monolayer to a resist film for electron beam lithography. The self-assembled monolayer deposited on a silicon dioxide surface by chemical vapor deposition is resistant to both sulfuric acid and hydrofluoric acid. By immersing the electron-beam-irradiated surface into both acids, we successfully develop microstructural patterns in the self-assembled monolayer. In particular, we show the effectiveness of immersing the substrate into a sulfuric-acid-based solution for the development of the pattern. The relationship between the required dose and the developing time is estimated by measuring the morphology of the developed patterns by atomic force microscopy. The pattern in the self-assembled monolayer can be transferred into both the underlying silicon dioxide layer and the silicon substrate. These results indicate that the organosilane self-assembled monolayer serves as an alternative resist for electron beam lithography.

Nanoscale patterns of modified oligonucleotides are produced on octadecyltrimethoxysilane self-assembled monolayers at a silicon surface by electron beam lithography. DNA structures with feature sizes of the order of 250 nm were detected by epifluorescence microscopy.

Nanoscale patterns of modified oligonucleotides are produced on octadecyltrimethoxysilane self-assembled monolayers at a silicon surface by electron beam lithography. DNA structures with feature sizes of the order of 250 nm were detected by epifluorescence microscopy.

Nanoscale patterns of modified oligonucleotides are produced on octadecyltrimethoxysilane self-assembled monolayers at a silicon surface by electron beam lithography. DNA structures with feature sizes of the order of 250 nm were detected by epifluorescence microscopy.

Large-scale SiO(2)/Si(111) models were constructed by introducing oxygen atoms in c-Si models in an atom-by-atom manner. Molecular dynamics calculation at a constant temperature was repeatedly carried out for the growing oxide model. By comparing the oxidation simulation of Si(111) substrate with that of Si(001) substrate performed previously, the influence of substrate orientation on the oxide structure was discussed. Owing to the significant feature of bonding arrangement within a Si bilayer in the Si(111) substrate, the inherent stress induced at the SiO(2)/Si interface by oxygen insertions is originally higher for the Si(111) oxidation than for the Si(001) oxidation, resulting in frequent changes in the bonding network. The resulting structure of bulk SiO(2) on Si(111) has less strain and a lower density than that on Si(001), but involves a larger number of dangling bonds. The X-ray diffraction pattern calculated for the SiO(2)/Si(111) model exhibits a diffraction peak with a Laue-function-like profile on each of the crystal-truncation-rods from the 111 and 11 (1) over bar points, agreeing well with experimental results. These diffraction peaks indicate that the thermally grown SiO(2) retains the residual order emanating from the {111} atomic planes in the original c-Si. Because of differences in the angles between the surface and the {111} atomic planes, the residual order within the SiO(2) differs depending on the substrate orientation.

By simulation of silicon oxidation and measurement of X-ray crystal-truncation-rod (CTR) scattering, the structures of silicon dioxide films grown at different temperatures and the structural changes due to thermal annealing have been investigated. Large-scale SiO2/Si(001) models were formed by introducing oxygen atoms, atom-by-atom, in crystalline Si from the surfaces. Molecular dynamics (MD) calculation at a constant temperature was repeatedly carried out for the growing oxide model. The intensity and position of the extra diffraction peak observed for the oxide, correlating with the residual order emanating from the parent Si crystal, depend on the growth temperature and change after thermal annealing. The peak intensity becomes smaller with increasing growth temperature. Thermal annealing monotonically decreases the peak intensity and shifts the position along the CTR,. toward the lower angle side. There is a good agreement between the results of simulation and experiment. It is shown that (1) the oxide grown At a higher temperature has a lower degree of residual order, (2) thermal annealing decreases the residual order, ultimately leads to complete amorphization and never restores the ordering, and (3) the peak shift along the CTR corresponds to the volumetric expansion of the SiO2 in the surface-normal direction.

By simulation of silicon oxidation and measurement of X-ray crystal-truncation-rod (CTR) scattering, the structures of silicon dioxide films grown at different temperatures and the structural changes due to thermal annealing have been investigated. Large-scale SiO2/Si(001) models were formed by introducing oxygen atoms, atom-by-atom, in crystalline Si from the surfaces. Molecular dynamics (MD) calculation at a constant temperature was repeatedly carried out for the growing oxide model. The intensity and position of the extra diffraction peak observed for the oxide, correlating with the residual order emanating from the parent Si crystal, depend on the growth temperature and change after thermal annealing. The peak intensity becomes smaller with increasing growth temperature. Thermal annealing monotonically decreases the peak intensity and shifts the position along the CTR,. toward the lower angle side. There is a good agreement between the results of simulation and experiment. It is shown that (1) the oxide grown At a higher temperature has a lower degree of residual order, (2) thermal annealing decreases the residual order, ultimately leads to complete amorphization and never restores the ordering, and (3) the peak shift along the CTR corresponds to the volumetric expansion of the SiO2 in the surface-normal direction.

By simulation of silicon oxidation and measurement of X-ray crystal-truncation-rod (CTR) scattering, the structures of silicon dioxide films grown at different temperatures and the structural changes due to thermal annealing have been investigated. Large-scale SiO2/Si(001) models were formed by introducing oxygen atoms, atom-by-atom, in crystalline Si from the surfaces. Molecular dynamics (MD) calculation at a constant temperature was repeatedly carried out for the growing oxide model. The intensity and position of the extra diffraction peak observed for the oxide, correlating with the residual order emanating from the parent Si crystal, depend on the growth temperature and change after thermal annealing. The peak intensity becomes smaller with increasing growth temperature. Thermal annealing monotonically decreases the peak intensity and shifts the position along the CTR,. toward the lower angle side. There is a good agreement between the results of simulation and experiment. It is shown that (1) the oxide grown At a higher temperature has a lower degree of residual order, (2) thermal annealing decreases the residual order, ultimately leads to complete amorphization and never restores the ordering, and (3) the peak shift along the CTR corresponds to the volumetric expansion of the SiO2 in the surface-normal direction.

It was found that the etch rate of Si in tetramethylammonium hydroxide (TMAH) solution is significantly retarded by introducing ion implantation damage.. By utilizing this new phenomenon, i.e., ion-bombardment-retarded etching (IBRE) of Si, a novel process to fabricate an ultrathin Si channel wall for the vertical double-gate (DG) metal-oxide-semiconductor field effect transistor (MOSFET) was developed. We succeeded in fabricating a vertical Si wall with thickness of 16 nm on bulk Si substrate with no introduction of dry etching damage. The effectiveness of thinning the Si channel wall to the characteristics of a vertical DG MOSFET was examined by means of simulations.

It was found that the etch rate of Si in tetramethylammonium hydroxide (TMAH) solution is significantly retarded by introducing ion implantation damage.. By utilizing this new phenomenon, i.e., ion-bombardment-retarded etching (IBRE) of Si, a novel process to fabricate an ultrathin Si channel wall for the vertical double-gate (DG) metal-oxide-semiconductor field effect transistor (MOSFET) was developed. We succeeded in fabricating a vertical Si wall with thickness of 16 nm on bulk Si substrate with no introduction of dry etching damage. The effectiveness of thinning the Si channel wall to the characteristics of a vertical DG MOSFET was examined by means of simulations.

It was found that the etch rate of Si in tetramethylammonium hydroxide (TMAH) solution is significantly retarded by introducing ion implantation damage.. By utilizing this new phenomenon, i.e., ion-bombardment-retarded etching (IBRE) of Si, a novel process to fabricate an ultrathin Si channel wall for the vertical double-gate (DG) metal-oxide-semiconductor field effect transistor (MOSFET) was developed. We succeeded in fabricating a vertical Si wall with thickness of 16 nm on bulk Si substrate with no introduction of dry etching damage. The effectiveness of thinning the Si channel wall to the characteristics of a vertical DG MOSFET was examined by means of simulations.

Focused ion-beam (FIB) optics in single-ion implantation (SII), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the necessary number is reached. has been modified in order to improve the controllability of dopant atom position to within 100 nm. The lateral magnification of the objective lens (OL) was remodeled to 1/19 from the original value of 1/6 before modification. Scanning ion microscope (SIM) images at a high magnification of 75,000 were taken using a 60 keV focused Si ion beam with a current of 1 pA to evaluate the resolution of secondary electron images. A diameter of the ion beam less than of 20 nm was obtained. One-by-one, 60 keV Si ions were implanted by means of SII into CR-39 which is a fission track detector for investigating the aiming precision. Deviation of the single ion incident site from the target position was evaluated using atomic force microscopy (AFM) and compared with that before modification of FIB optics. The average aiming precision in SII was improved to be 60 nm which was 1/3 of that before modification.

Focused ion-beam (FIB) optics in single-ion implantation (SII), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the necessary number is reached. has been modified in order to improve the controllability of dopant atom position to within 100 nm. The lateral magnification of the objective lens (OL) was remodeled to 1/19 from the original value of 1/6 before modification. Scanning ion microscope (SIM) images at a high magnification of 75,000 were taken using a 60 keV focused Si ion beam with a current of 1 pA to evaluate the resolution of secondary electron images. A diameter of the ion beam less than of 20 nm was obtained. One-by-one, 60 keV Si ions were implanted by means of SII into CR-39 which is a fission track detector for investigating the aiming precision. Deviation of the single ion incident site from the target position was evaluated using atomic force microscopy (AFM) and compared with that before modification of FIB optics. The average aiming precision in SII was improved to be 60 nm which was 1/3 of that before modification.

Focused ion-beam (FIB) optics in single-ion implantation (SII), which enables us to implant dopant ions one-by-one into a fine semiconductor region until the necessary number is reached. has been modified in order to improve the controllability of dopant atom position to within 100 nm. The lateral magnification of the objective lens (OL) was remodeled to 1/19 from the original value of 1/6 before modification. Scanning ion microscope (SIM) images at a high magnification of 75,000 were taken using a 60 keV focused Si ion beam with a current of 1 pA to evaluate the resolution of secondary electron images. A diameter of the ion beam less than of 20 nm was obtained. One-by-one, 60 keV Si ions were implanted by means of SII into CR-39 which is a fission track detector for investigating the aiming precision. Deviation of the single ion incident site from the target position was evaluated using atomic force microscopy (AFM) and compared with that before modification of FIB optics. The average aiming precision in SII was improved to be 60 nm which was 1/3 of that before modification.

Large-scale modeling of ultra-thin SiO₂ films on Si(001) surfaces has been performed by means of molecular dynamics utilizing our original inter-atomic potential energy function for Si, O mixed systems. The SiO₂ film is formed by layer-by-layer insertion of O atoms into Si-Si bonds in a Si wafer from the surface. The obtained models reproduce quantitatively the structural transition layers near the interface. Through a modeling of vicinal SiO₂/Si(001) model including atomic steps, it has been found that oxide film near the step-edge is preferentially amorphized. For a more advanced modeling method, we propose a new simulation procedure where O atoms are introduced into the substrate in one-by-one manner. In the calculation, the oxidation is started from the surface and abrupt change in composition at the SiO₂/Si interface is reproduced. Thus, the classical molecular dynamics is a powerful method together with a simplified inter-atomic potential function applicable to mixed systems.

極微構造半導体デバイスにおいて顕在化する不純物原子数あゆらぎによるデバイス特性のゆらぎを解消するために,現在シングルイオン注入技術の開発を進めている.開発の現状と課題を紹介し,また,固体表面・界面,あるいはデバイスへの照射効果,ならびにシリコン中の点欠陥の挙動を解明する手段としての応用の可能性を論じた.