Publications
ResearcherID : C-5956-2008 (TY, h-index: 23) , AAZ-8749-2021 (RK, h-index: 7)
Google Scholar : TY (h-index: 32), RK (h-index: 8)
2010
Sotaro Yukutake, Tadashi Kawazoe, Takashi Yatsui, Wataru Nomura, Kokoro Kitamura, Motoichi Ohtsu
In: Applied Physics B, 99 (3), pp. 415-422, 2010.
Abstract | Links | BibTeX | Tags: Nanophotonic fabrication, Near-field effect, Self-assembly
@article{2010yukutakeAPB,
title = {Selective photocurrent generation in the transparent wavelength range of a semiconductor photovoltaic device using a phonon-assisted optical near-field process},
author = {Sotaro Yukutake and Tadashi Kawazoe and Takashi Yatsui and Wataru Nomura and Kokoro Kitamura and Motoichi Ohtsu},
doi = {10.1007/s00340-010-3999-5},
year = {2010},
date = {2010-05-01},
journal = {Applied Physics B},
volume = {99},
number = {3},
pages = {415-422},
publisher = {Springer Nature},
abstract = {In this paper, we propose a novel photovoltaic device using P3HT and ZnO as test materials for the ptype and n-type semiconductors, respectively. To fabricate an electrode of this device, Ag was deposited on a P3HT film by RF-sputtering under light illumination (wavelength λ0 = 660 nm) while reversely biasing the P3HT/ZnO pnjunction. As a result, a unique granular Ag film was formed, which originated from a phonon-assisted process induced by an optical near-field in a self-organized manner. The fabricated device generated a photocurrent even though the incident light wavelength was as long as 670 nm, which is longer than the long-wavelength cutoff λc (= 570 nm) of the P3HT. The photocurrent was generated in a wavelength-selective manner, showing a maximum at the incident light wavelength of 620 nm, which was shorter than λ0 because of the Stark effect brought about by the reverse bias DC electric field applied during the Ag deposition.},
keywords = {Nanophotonic fabrication, Near-field effect, Self-assembly},
pubstate = {published},
tppubtype = {article}
}
In this paper, we propose a novel photovoltaic device using P3HT and ZnO as test materials for the ptype and n-type semiconductors, respectively. To fabricate an electrode of this device, Ag was deposited on a P3HT film by RF-sputtering under light illumination (wavelength λ0 = 660 nm) while reversely biasing the P3HT/ZnO pnjunction. As a result, a unique granular Ag film was formed, which originated from a phonon-assisted process induced by an optical near-field in a self-organized manner. The fabricated device generated a photocurrent even though the incident light wavelength was as long as 670 nm, which is longer than the long-wavelength cutoff λc (= 570 nm) of the P3HT. The photocurrent was generated in a wavelength-selective manner, showing a maximum at the incident light wavelength of 620 nm, which was shorter than λ0 because of the Stark effect brought about by the reverse bias DC electric field applied during the Ag deposition.
Takashi Yatsui, Yang Ryu, Tetsu Morishima, Wataru Nomura, Tadashi Kawazoe, Tetsu Yonezawa, Masao Washizu, Hiroyuki Fujita, Motoichi Ohtsu
Self-assembly method of linearly aligning ZnO quantum dots for a nanophotonic signal transmission device Journal Article
In: Applied Physics Letters, 96 (13), pp. 133106, 2010.
Abstract | Links | BibTeX | Tags: First, Nanophotonic device, QD, Self-assembly, ZnO
@article{doi:10.1063/1.3372639,
title = {Self-assembly method of linearly aligning ZnO quantum dots for a nanophotonic signal transmission device},
author = {Takashi Yatsui and Yang Ryu and Tetsu Morishima and Wataru Nomura and Tadashi Kawazoe and Tetsu Yonezawa and Masao Washizu and Hiroyuki Fujita and Motoichi Ohtsu},
url = {https://doi.org/10.1063/1.3372639},
doi = {10.1063/1.3372639},
year = {2010},
date = {2010-01-01},
journal = {Applied Physics Letters},
volume = {96},
number = {13},
pages = {133106},
abstract = {We report a self-assembly method that aligns nanometer-sized quantum dots (QDs) into a straight line along which photonic signals can be transmitted by optically near-field effects. ZnO QDs were bound electrostatically to DNA to form a one-dimensional QD chain. The photoluminescence intensity under parallel polarization excitation along the QDs chain was much greater than under perpendicular polarization excitation, indicating an efficient signal transmission along the QD chain. As optical near-field energy can transmit through the resonant energy level, nanophotonic signal transmission devices have a number of potential applications, such as wavelength division multiplexing using QDs of different sizes.},
keywords = {First, Nanophotonic device, QD, Self-assembly, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report a self-assembly method that aligns nanometer-sized quantum dots (QDs) into a straight line along which photonic signals can be transmitted by optically near-field effects. ZnO QDs were bound electrostatically to DNA to form a one-dimensional QD chain. The photoluminescence intensity under parallel polarization excitation along the QDs chain was much greater than under perpendicular polarization excitation, indicating an efficient signal transmission along the QD chain. As optical near-field energy can transmit through the resonant energy level, nanophotonic signal transmission devices have a number of potential applications, such as wavelength division multiplexing using QDs of different sizes.
2009
Takashi Yatsui, Shunsuke Yamazaki, Keiichi Ito, Hiroshi Kawamura, Michinobu Mizumura, Tadashi Kawazoe, Motoichi Ohtsu
Increased spatial homogeneity in a light-emitting InGaN thin film using optical near-field desorption Journal Article
In: Applied Physics B, 97 (2), pp. 375-378, 2009.
Abstract | Links | BibTeX | Tags: First, GaN, Nanophotonic fabrication, Near-field effect, Self-assembly
@article{2009yatsuiGaNAPB,
title = {Increased spatial homogeneity in a light-emitting InGaN thin film using optical near-field desorption},
author = {Takashi Yatsui and Shunsuke Yamazaki and Keiichi Ito and Hiroshi Kawamura and Michinobu Mizumura and Tadashi Kawazoe and Motoichi Ohtsu},
doi = {10.1007/s00340-009-3757-8},
year = {2009},
date = {2009-10-01},
journal = {Applied Physics B},
volume = {97},
number = {2},
pages = {375-378},
publisher = {Springer Nature},
abstract = {We report a self-assembly method that produces greater spatial uniformity in InGaN thin films using optical near-field desorption. Spatial homogeneity in the In fraction was reduced by introducing additional light during the photo-enhanced chemical vapor deposition of InGaN. Near-field desorption of InGaN nanoparticles, upon addition depended on the In content of the film, and the photon energy of the illumination source determined the energy of the emitted photons. Since this deposition method is based on a photo-desorption reaction, it can easily be applied to other deposition techniques and used with other semiconductor systems.},
keywords = {First, GaN, Nanophotonic fabrication, Near-field effect, Self-assembly},
pubstate = {published},
tppubtype = {article}
}
We report a self-assembly method that produces greater spatial uniformity in InGaN thin films using optical near-field desorption. Spatial homogeneity in the In fraction was reduced by introducing additional light during the photo-enhanced chemical vapor deposition of InGaN. Near-field desorption of InGaN nanoparticles, upon addition depended on the In content of the film, and the photon energy of the illumination source determined the energy of the emitted photons. Since this deposition method is based on a photo-desorption reaction, it can easily be applied to other deposition techniques and used with other semiconductor systems.
Takashi Yatsui, Motoichi Ohtsu
Production of size-controlled Si nanocrystals using self-organized optical near-field chemical etching Journal Article
In: Applied Physics Letters, 95 (4), pp. 043104, 2009.
Abstract | Links | BibTeX | Tags: First, Nanophotonic fabrication, Near-field effect, Self-assembly, Si
@article{doi:10.1063/1.3193536,
title = {Production of size-controlled Si nanocrystals using self-organized optical near-field chemical etching},
author = {Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1063/1.3193536},
year = {2009},
date = {2009-07-24},
journal = {Applied Physics Letters},
volume = {95},
number = {4},
pages = {043104},
abstract = {We demonstrate the selective photochemical etching of Si in a self-organized manner, which strongly depends on the distribution of the optical near field. This dependence was described by the virtual exciton-phonon-polariton model. The photoluminescence (PL) spectra from the etched Si exhibited a blueshifted PL peak at 1.8 eV, corresponding to Si nanocrystals of 2.8 nm diameter.},
keywords = {First, Nanophotonic fabrication, Near-field effect, Self-assembly, Si},
pubstate = {published},
tppubtype = {article}
}
We demonstrate the selective photochemical etching of Si in a self-organized manner, which strongly depends on the distribution of the optical near field. This dependence was described by the virtual exciton-phonon-polariton model. The photoluminescence (PL) spectra from the etched Si exhibited a blueshifted PL peak at 1.8 eV, corresponding to Si nanocrystals of 2.8 nm diameter.
2007
Makoto Naruse, Takashi Yatsui, Kokoro Kitamura, Hirokazu Hori, Motoichi Ohtsu
Generating small-scale structures from large-scale ones via optical near-field interactions Journal Article
In: Optics Express, 15 (19), pp. 11790-11797, 2007.
Abstract | Links | BibTeX | Tags: Nanophotonic fabrication, Near-field effect, Self-assembly
@article{Naruse:s,
title = {Generating small-scale structures from large-scale ones via optical near-field interactions},
author = {Makoto Naruse and Takashi Yatsui and Kokoro Kitamura and Hirokazu Hori and Motoichi Ohtsu},
doi = {10.1364/OE.15.011790},
year = {2007},
date = {2007-09-01},
journal = {Optics Express},
volume = {15},
number = {19},
pages = {11790-11797},
publisher = {OSA},
abstract = {Optical near-fields, which appear in the vicinity of structures when irradiated with light, exhibit a hierarchical nature, meaning that the degree of localization of optical near-fields at a given point is related to the scale of the structure involved in this process. Therefore, if we could make optically induced fabrication processes selectively localized in the near-field region, we could generate a smaller-scale structure even from a larger-scale one via optical near-field interactions. We demonstrate the theoretical basis of this with an angular spectrum analysis of optical near-fields. We also experimentally demonstrate such principles by using ZnO nanoneedles fabricated through metal-organic vapor phase epitaxy (MOVPE) followed by a photo-induced MOVPE procedure where smaller-scale generated structures were clearly observed with the help of light irradiation. We also observed that the generated fine structures followed a power-law distribution, indicating that fractal structures emerged via optical near-field interactions.},
keywords = {Nanophotonic fabrication, Near-field effect, Self-assembly},
pubstate = {published},
tppubtype = {article}
}
Optical near-fields, which appear in the vicinity of structures when irradiated with light, exhibit a hierarchical nature, meaning that the degree of localization of optical near-fields at a given point is related to the scale of the structure involved in this process. Therefore, if we could make optically induced fabrication processes selectively localized in the near-field region, we could generate a smaller-scale structure even from a larger-scale one via optical near-field interactions. We demonstrate the theoretical basis of this with an angular spectrum analysis of optical near-fields. We also experimentally demonstrate such principles by using ZnO nanoneedles fabricated through metal-organic vapor phase epitaxy (MOVPE) followed by a photo-induced MOVPE procedure where smaller-scale generated structures were clearly observed with the help of light irradiation. We also observed that the generated fine structures followed a power-law distribution, indicating that fractal structures emerged via optical near-field interactions.
2005
Takashi Yatsui, Wataru Nomura, Motoichi Ohtsu
Self-Assembly of Size- and Position-Controlled Ultralong Nanodot Chains using Near-Field Optical Desorption Journal Article
In: Nano Letters, 5 (12), pp. 2548-2551, 2005, (PMID: 16351213).
Abstract | Links | BibTeX | Tags: First, Nanophotonic fabrication, Plasmon, Selected, Self-assembly
@article{doi:10.1021/nl051898z,
title = {Self-Assembly of Size- and Position-Controlled Ultralong Nanodot Chains using Near-Field Optical Desorption},
author = {Takashi Yatsui and Wataru Nomura and Motoichi Ohtsu},
doi = {10.1021/nl051898z},
year = {2005},
date = {2005-12-01},
journal = {Nano Letters},
volume = {5},
number = {12},
pages = {2548-2551},
abstract = {We report the self-assembly of a size- and position-controlled ultralong nanodot chain using a novel effect of near-field optical desorption. A sub-100-nm dot chain with a deviation of 5 nm forms at a size based on plasmon resonance, depending on the photon energy; the resulting structure forms a high-transmission-efficiency nanoscale waveguide. Using this method with simple lithographically patterned substrates allows one to increase the throughput of the production of nanoscale structures dramatically at all scales.},
note = {PMID: 16351213},
keywords = {First, Nanophotonic fabrication, Plasmon, Selected, Self-assembly},
pubstate = {published},
tppubtype = {article}
}
We report the self-assembly of a size- and position-controlled ultralong nanodot chain using a novel effect of near-field optical desorption. A sub-100-nm dot chain with a deviation of 5 nm forms at a size based on plasmon resonance, depending on the photon energy; the resulting structure forms a high-transmission-efficiency nanoscale waveguide. Using this method with simple lithographically patterned substrates allows one to increase the throughput of the production of nanoscale structures dramatically at all scales.
Takashi Yatsui, Wataru Nomura, Motoichi Ohtsu
Size-, Position-, and Separation-Controlled One-Dimensional Alignment of Nanoparticles Using an Optical Near Field Journal Article
In: IEICE TRANSACTIONS on Electronics, E88-C (9), pp. 1798-1802, 2005.
Abstract | Links | BibTeX | Tags: First, Nanophotonic fabrication, Self-assembly
@article{2005IEICE,
title = {Size-, Position-, and Separation-Controlled One-Dimensional Alignment of Nanoparticles Using an Optical Near Field},
author = {Takashi Yatsui and Wataru Nomura and Motoichi Ohtsu},
doi = {10.1093/ietele/e88-c.9.1798},
year = {2005},
date = {2005-09-01},
journal = {IEICE TRANSACTIONS on Electronics},
volume = {E88-C},
number = {9},
pages = {1798-1802},
publisher = {IEICE},
abstract = {Particles several tens of nanometers in size were aligned in the desired positions in a controlled manner by using capillary force interaction and suspension flow. Latex beads 40-nm in diameter were aligned linearly around a 10-um-hole template fabricated by lithography. Further control of their position and separation was realized using colloidal gold nanoparticles by controlling the particle-substrate and particle-particle interactions using an optical near field generated on the edge of a Si wedge, in which the separation of the colloidal gold nanoparticles was controlled by the direction of polarization.},
keywords = {First, Nanophotonic fabrication, Self-assembly},
pubstate = {published},
tppubtype = {article}
}
Particles several tens of nanometers in size were aligned in the desired positions in a controlled manner by using capillary force interaction and suspension flow. Latex beads 40-nm in diameter were aligned linearly around a 10-um-hole template fabricated by lithography. Further control of their position and separation was realized using colloidal gold nanoparticles by controlling the particle-substrate and particle-particle interactions using an optical near field generated on the edge of a Si wedge, in which the separation of the colloidal gold nanoparticles was controlled by the direction of polarization.
2003
Takashi Yatsui, Akira Takubo, Jungshik Lim, Wataru Nomura, Motonobu Kourogi, Motoichi Ohtsu
Regulating the size and position of deposited Zn nanoparticles by optical near-field desorption using size-dependent resonance Journal Article
In: Applied Physics Letters, 83 (9), pp. 1716-1718, 2003.
Abstract | Links | BibTeX | Tags: First, Self-assembly, Size-dependent resonance
@article{doi:10.1063/1.1606883,
title = {Regulating the size and position of deposited Zn nanoparticles by optical near-field desorption using size-dependent resonance},
author = {Takashi Yatsui and Akira Takubo and Jungshik Lim and Wataru Nomura and Motonobu Kourogi and Motoichi Ohtsu},
doi = {10.1063/1.1606883},
year = {2003},
date = {2003-09-01},
journal = {Applied Physics Letters},
volume = {83},
number = {9},
pages = {1716-1718},
abstract = {We report that optical near-field desorption can dramatically regulate the growth of Zn nanoparticles during optical chemical vapor deposition. The trade off between the deposition due to 3.81 eV optical near-field light and desorption due to 2.54 eV optical near-field light allowed the fabrication of a single 15 nm Zn dot, while regulating its size and position.},
keywords = {First, Self-assembly, Size-dependent resonance},
pubstate = {published},
tppubtype = {article}
}
We report that optical near-field desorption can dramatically regulate the growth of Zn nanoparticles during optical chemical vapor deposition. The trade off between the deposition due to 3.81 eV optical near-field light and desorption due to 2.54 eV optical near-field light allowed the fabrication of a single 15 nm Zn dot, while regulating its size and position.