Publications
ResearcherID : C-5956-2008 (TY, h-index: 23) , AAZ-8749-2021 (RK, h-index: 6)
Google Scholar : TY (h-index: 32), RK (h-index: 7)
2014
Hiroaki Matsui, Wasanthamala Badalawa, Takayuki Hasebe, Shinya Furuta, Wataru Nomura, Takashi Yatsui, Motoichi Ohtsu, Hitoshi Tabata
Coupling of Er light emissions to plasmon modes on In2O3: Sn nanoparticle sheets in the near-infrared range Journal Article
In: Applied Physics Letters, 105 (4), pp. 041903, 2014.
Abstract | Links | BibTeX | Tags: In2O3: Sn, Plasmon, ZnO
@article{2014Matsui,
title = {Coupling of Er light emissions to plasmon modes on In2O3: Sn nanoparticle sheets in the near-infrared range},
author = {Hiroaki Matsui and Wasanthamala Badalawa and Takayuki Hasebe and Shinya Furuta and Wataru Nomura and Takashi Yatsui and Motoichi Ohtsu and Hitoshi Tabata},
doi = {10.1063/1.4892004},
year = {2014},
date = {2014-07-01},
journal = {Applied Physics Letters},
volume = {105},
number = {4},
pages = {041903},
abstract = {Near-infrared Er photoluminescence (PL) is markedly modified using a plasmonic In2O3: Sn nanoparticle (NP) sheet. Modeling and optical measurements reveal the presence of different electric fields (E-field) in the NP sheet. The local E-field excited at the interface between the NP sheet and Er-emitting layer of ZnO contributes significantly towards the spectral modifications of Er PL due to matching with the photon energy of Er PL. We also determine the critical temperature for Er PL modifications, which is related to the energy transfer efficiency between Er transition dipoles in ZnO and the plasmon modes on the NP sheet.},
keywords = {In2O3: Sn, Plasmon, ZnO},
pubstate = {published},
tppubtype = {article}
}
Near-infrared Er photoluminescence (PL) is markedly modified using a plasmonic In2O3: Sn nanoparticle (NP) sheet. Modeling and optical measurements reveal the presence of different electric fields (E-field) in the NP sheet. The local E-field excited at the interface between the NP sheet and Er-emitting layer of ZnO contributes significantly towards the spectral modifications of Er PL due to matching with the photon energy of Er PL. We also determine the critical temperature for Er PL modifications, which is related to the energy transfer efficiency between Er transition dipoles in ZnO and the plasmon modes on the NP sheet.
Takashi Yatsui, Tsubasa Imoto, Takahiro Mochizuki, Kokoro Kitamura, Tadashi Kawazoe
Dressed-photon–phonon (DPP)-assisted visible- and infrared-light water splitting Journal Article
In: Scientific Reports, 4 , pp. 4561, 2014.
Abstract | Links | BibTeX | Tags: First, Non-uniform optical near field, Water splitting, ZnO
@article{2014water,
title = {Dressed-photon–phonon (DPP)-assisted visible- and infrared-light water splitting},
author = {Takashi Yatsui and Tsubasa Imoto and Takahiro Mochizuki and Kokoro Kitamura and Tadashi Kawazoe},
doi = {10.1038/srep04561},
year = {2014},
date = {2014-04-01},
journal = {Scientific Reports},
volume = {4},
pages = {4561},
publisher = {Springer Nature},
abstract = {A dressed-phonon–phonon (DPP) assisted photocatalyst reaction was carried out to increase the visible light responsibility, where the photon energy of the radiation, which ranged from visible to infrared light is less than band gap energy of the photocatalyst (ZnO, 3.3 eV). The dependence of the photocurrent on excitation power indicated that two-step excitation occurred in DPP-assisted process. A cathodoluminescence measurement also supported the conclusion that the visible- and infrared-light excitation originated from DPP excitation, not from defect states in the ZnO nanorod photocatalyst.},
keywords = {First, Non-uniform optical near field, Water splitting, ZnO},
pubstate = {published},
tppubtype = {article}
}
A dressed-phonon–phonon (DPP) assisted photocatalyst reaction was carried out to increase the visible light responsibility, where the photon energy of the radiation, which ranged from visible to infrared light is less than band gap energy of the photocatalyst (ZnO, 3.3 eV). The dependence of the photocurrent on excitation power indicated that two-step excitation occurred in DPP-assisted process. A cathodoluminescence measurement also supported the conclusion that the visible- and infrared-light excitation originated from DPP excitation, not from defect states in the ZnO nanorod photocatalyst.
2012
Yang Liu, Takashi Yatsui, Motoichi Ohtsu
Controlling the sizes of ZnO quantum dots by using dressed photon-phonon assisted sol-gel method Journal Article
In: Applied Physics B, 108 (4), pp. 707-711, 2012.
Abstract | Links | BibTeX | Tags: Nanophotonic fabrication, Near-field effect, QD, Sol-gel, ZnO
@article{2012liuAPB,
title = {Controlling the sizes of ZnO quantum dots by using dressed photon-phonon assisted sol-gel method},
author = {Yang Liu and Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1007/s00340-012-5151-1},
year = {2012},
date = {2012-09-01},
journal = {Applied Physics B},
volume = {108},
number = {4},
pages = {707-711},
publisher = {Springer Nature},
abstract = {We developed a sol-gel method using the dressed photon-phonon (DPP) process. DPPs are selectively exited in nanoscale structures at photon energies that are lower than the bandgap energy, which allows one to increase the growth rate of smaller ZnO quantum dots (QDs). Thus, we obtained a smaller size variance of ZnO QDs. The growth rate was proportional to the power of the light used for DPP excitation. The results were confirmed using a rate equation that accounted for the concentration of the sol-gel solution.},
keywords = {Nanophotonic fabrication, Near-field effect, QD, Sol-gel, ZnO},
pubstate = {published},
tppubtype = {article}
}
We developed a sol-gel method using the dressed photon-phonon (DPP) process. DPPs are selectively exited in nanoscale structures at photon energies that are lower than the bandgap energy, which allows one to increase the growth rate of smaller ZnO quantum dots (QDs). Thus, we obtained a smaller size variance of ZnO QDs. The growth rate was proportional to the power of the light used for DPP excitation. The results were confirmed using a rate equation that accounted for the concentration of the sol-gel solution.
Takashi Yatsui, Akira Ishikawa, Kiyoshi Kobayashi, Akira Shojiguchi, Suguru Sangu, Tadashi Kawazoe, Motoichi Ohtsu, Jinkyoung Yoo, Gyu-Chul Yi
Superradiance from one-dimensionally aligned ZnO nanorod multiple-quantum-well structures Journal Article
In: Applied Physics Letters, 100 (23), pp. 233118, 2012.
Abstract | Links | BibTeX | Tags: First, nanorod, Superradiance, ZnO
@article{doi:10.1063/1.4725514,
title = {Superradiance from one-dimensionally aligned ZnO nanorod multiple-quantum-well structures},
author = {Takashi Yatsui and Akira Ishikawa and Kiyoshi Kobayashi and Akira Shojiguchi and Suguru Sangu and Tadashi Kawazoe and Motoichi Ohtsu and Jinkyoung Yoo and Gyu-Chul Yi},
doi = {10.1063/1.4725514},
year = {2012},
date = {2012-05-01},
journal = {Applied Physics Letters},
volume = {100},
number = {23},
pages = {233118},
abstract = {Using one-dimensionally aligned ZnO nanorod multiple-quantum-well structures (MQWs), we observed a superradiance, i.e., a cooperative spontaneous emission. We confirmed that the excitation power dependence of the emissions from the MQWs originated from the coherent coupling of the QWs due to the well organization at nanoscale. We identified two QWs with cooperative emission. Additionally, we evaluated the number of coherently coupled QWs sets of four that resulted in the superradiance. Our findings provide criteria for designing nanoscale synergetic devices without the use of an external cavity.},
keywords = {First, nanorod, Superradiance, ZnO},
pubstate = {published},
tppubtype = {article}
}
Using one-dimensionally aligned ZnO nanorod multiple-quantum-well structures (MQWs), we observed a superradiance, i.e., a cooperative spontaneous emission. We confirmed that the excitation power dependence of the emissions from the MQWs originated from the coherent coupling of the QWs due to the well organization at nanoscale. We identified two QWs with cooperative emission. Additionally, we evaluated the number of coherently coupled QWs sets of four that resulted in the superradiance. Our findings provide criteria for designing nanoscale synergetic devices without the use of an external cavity.
Takashi Yatsui, Kosuke Nakanishi, Kokoro Kitamura, Motoichi Ohtsu
Room-temperature growth of high-quality ZnO nanocrystals using a dressed-photon-assisted near-field process Journal Article
In: Applied Physics B, 107 (3), pp. 637-641, 2012.
Abstract | Links | BibTeX | Tags: First, Near-field effect, ZnO
@article{2012yatsuiAPB,
title = {Room-temperature growth of high-quality ZnO nanocrystals using a dressed-photon-assisted near-field process},
author = {Takashi Yatsui and Kosuke Nakanishi and Kokoro Kitamura and Motoichi Ohtsu},
doi = {10.1007/s00340-012-5076-8},
year = {2012},
date = {2012-05-01},
journal = {Applied Physics B},
volume = {107},
number = {3},
pages = {637-641},
publisher = {Springer Nature},
abstract = {Single-crystalline ZnO nanocrystals were fabricated by room-temperature photo-chemical vapor deposition (PCVD). We further enhanced the growth of high-quality single-crystalline ZnO nanocrystals using dressed photons and phonons (DPPs). This resulted in greater position control and the growth of high-quality ZnO nanocrystals. The ZnO nanocrystals produced with DPPs had excellent cathodoluminescence characteristics, indicating that the near-field PCVD process could be a promising technique for nanophotonic integrated circuit production.},
keywords = {First, Near-field effect, ZnO},
pubstate = {published},
tppubtype = {article}
}
Single-crystalline ZnO nanocrystals were fabricated by room-temperature photo-chemical vapor deposition (PCVD). We further enhanced the growth of high-quality single-crystalline ZnO nanocrystals using dressed photons and phonons (DPPs). This resulted in greater position control and the growth of high-quality ZnO nanocrystals. The ZnO nanocrystals produced with DPPs had excellent cathodoluminescence characteristics, indicating that the near-field PCVD process could be a promising technique for nanophotonic integrated circuit production.
Takashi Yatsui, Masahiro Tsuji, Yang Liu, Tadashi Kawazoe, Motoichi Ohtsu
Emission from a dipole-forbidden energy state in a ZnO quantum dot induced by a near-field interaction with a fiber probe Journal Article
In: Applied Physics Letters, 100 (22), pp. 223110, 2012.
Abstract | Links | BibTeX | Tags: First, Near-field effect, QD, ZnO
@article{doi:10.1063/1.4723574,
title = {Emission from a dipole-forbidden energy state in a ZnO quantum dot induced by a near-field interaction with a fiber probe},
author = {Takashi Yatsui and Masahiro Tsuji and Yang Liu and Tadashi Kawazoe and Motoichi Ohtsu},
doi = {10.1063/1.4723574},
year = {2012},
date = {2012-05-01},
journal = {Applied Physics Letters},
volume = {100},
number = {22},
pages = {223110},
abstract = {The emission intensity from the dipole-forbidden state in a spherical quantum dot (QD) was enhanced by introducing an aperture fiber probe close to the ZnO QD to induce a near-field interaction between the probe tip and the QD. The cross-sectional profiles of the photoluminescence intensities of the ground exciton state and the excited exciton states varied spatially in an anti-correlated manner.},
keywords = {First, Near-field effect, QD, ZnO},
pubstate = {published},
tppubtype = {article}
}
The emission intensity from the dipole-forbidden state in a spherical quantum dot (QD) was enhanced by introducing an aperture fiber probe close to the ZnO QD to induce a near-field interaction between the probe tip and the QD. The cross-sectional profiles of the photoluminescence intensities of the ground exciton state and the excited exciton states varied spatially in an anti-correlated manner.
2010
Stephen Schmidt, Manfred Mascheck, Martin Silies, Takashi Yatsui, Kokoro Kitamura, Motoichi Ohtsu, Christoph Lienau
In: Optics Express, 18 (24), pp. 25016–25028, 2010.
Abstract | Links | BibTeX | Tags: SHG, ZnO
@article{Schmidt:10,
title = {Distinguishing between ultrafast optical harmonic generation and multi-photon-induced luminescence from ZnO thin films by frequency-resolved interferometric autocorrelation microscopy},
author = {Stephen Schmidt and Manfred Mascheck and Martin Silies and Takashi Yatsui and Kokoro Kitamura and Motoichi Ohtsu and Christoph Lienau},
doi = {10.1364/OE.18.025016},
year = {2010},
date = {2010-11-01},
journal = {Optics Express},
volume = {18},
number = {24},
pages = {25016--25028},
publisher = {OSA},
abstract = {The nonlinear optical properties of thin ZnO film are studied using interferometric autocorrelation (IFRAC) microscopy. Ultrafast, below-bandgap excitation with 6-fs laser pulses at 800 nm focused to a spot size of 1 textmum results in two emission bands in the blue and blue-green spectral region with distinctly different coherence properties. We show that an analysis of the wavelength-dependence of the interference fringes in the IFRAC signal allows for an unambiguous assignment of these bands as coherent second harmonic emission and incoherent, multiphoton-induced photoluminescence, respectively. More generally our analysis shows that IFRAC allows for a complete characterization of the coherence properties of the nonlinear optical emission from nanostructures in a single-beam experiment. Since this technique combines a very high temporal and spatial resolution we anticipate broad applications in nonlinear nano-optics.},
keywords = {SHG, ZnO},
pubstate = {published},
tppubtype = {article}
}
The nonlinear optical properties of thin ZnO film are studied using interferometric autocorrelation (IFRAC) microscopy. Ultrafast, below-bandgap excitation with 6-fs laser pulses at 800 nm focused to a spot size of 1 textmum results in two emission bands in the blue and blue-green spectral region with distinctly different coherence properties. We show that an analysis of the wavelength-dependence of the interference fringes in the IFRAC signal allows for an unambiguous assignment of these bands as coherent second harmonic emission and incoherent, multiphoton-induced photoluminescence, respectively. More generally our analysis shows that IFRAC allows for a complete characterization of the coherence properties of the nonlinear optical emission from nanostructures in a single-beam experiment. Since this technique combines a very high temporal and spatial resolution we anticipate broad applications in nonlinear nano-optics.
Kokoro Kitamura, Takashi Yatsui, Tadashi Kawazoe, Masakazu Sugiyama, Motoichi Ohtsu
Site-selective deposition of gold nanoparticles using non-adiabatic reaction induced by optical near-fields Journal Article
In: Nanotechnology, 21 (28), pp. 285302, 2010.
Abstract | Links | BibTeX | Tags: Nanophotonic fabrication, nanorod, Near-field effect, ZnO
@article{Kitamura_2010,
title = {Site-selective deposition of gold nanoparticles using non-adiabatic reaction induced by optical near-fields},
author = {Kokoro Kitamura and Takashi Yatsui and Tadashi Kawazoe and Masakazu Sugiyama and Motoichi Ohtsu},
doi = {10.1088/0957-4484/21/28/285302},
year = {2010},
date = {2010-06-01},
journal = {Nanotechnology},
volume = {21},
number = {28},
pages = {285302},
publisher = {IOP Publishing},
abstract = {In this paper, we report on site-selective deposition of metal nanoparticles
using a non-adiabatic photochemical reaction. Photoreduction of gold
was performed in a silica gel membrane containing tetrachloroaurate (AuCl4 − ) ions, using ZnO nanorods as the sources of optical near-field light, resulting in deposition
of gold nanoparticles with an average diameter of 17.7 nm. The distribution of
distances between the gold nanoparticles and nanorod traces revealed that the gold
nanoparticles were deposited adjacent to the ZnO nanorods, reflecting the attenuation of
the optical near-fields in the vicinity of the ZnO nanorods. We found that the
emission wavelength from the ZnO nanorods was longer than the absorption edge
wavelength of the tetrachloroaurate. Additionally, from the intensity distribution
obtained by a finite-difference time-domain method, the gold deposited around the
ZnO nanorods was found to be due to a non-adiabatic photochemical reaction.},
keywords = {Nanophotonic fabrication, nanorod, Near-field effect, ZnO},
pubstate = {published},
tppubtype = {article}
}
In this paper, we report on site-selective deposition of metal nanoparticles
using a non-adiabatic photochemical reaction. Photoreduction of gold
was performed in a silica gel membrane containing tetrachloroaurate (AuCl4 − ) ions, using ZnO nanorods as the sources of optical near-field light, resulting in deposition
of gold nanoparticles with an average diameter of 17.7 nm. The distribution of
distances between the gold nanoparticles and nanorod traces revealed that the gold
nanoparticles were deposited adjacent to the ZnO nanorods, reflecting the attenuation of
the optical near-fields in the vicinity of the ZnO nanorods. We found that the
emission wavelength from the ZnO nanorods was longer than the absorption edge
wavelength of the tetrachloroaurate. Additionally, from the intensity distribution
obtained by a finite-difference time-domain method, the gold deposited around the
ZnO nanorods was found to be due to a non-adiabatic photochemical reaction.
using a non-adiabatic photochemical reaction. Photoreduction of gold
was performed in a silica gel membrane containing tetrachloroaurate (AuCl4 − ) ions, using ZnO nanorods as the sources of optical near-field light, resulting in deposition
of gold nanoparticles with an average diameter of 17.7 nm. The distribution of
distances between the gold nanoparticles and nanorod traces revealed that the gold
nanoparticles were deposited adjacent to the ZnO nanorods, reflecting the attenuation of
the optical near-fields in the vicinity of the ZnO nanorods. We found that the
emission wavelength from the ZnO nanorods was longer than the absorption edge
wavelength of the tetrachloroaurate. Additionally, from the intensity distribution
obtained by a finite-difference time-domain method, the gold deposited around the
ZnO nanorods was found to be due to a non-adiabatic photochemical reaction.
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
Kokoro Kitamura, Takashi Yatsui, Motoichi Ohtsu
Observation of quantum confinement in ZnO nanorods fabricated using a two-temperature growth method Journal Article
In: Applied Physics B, 97 (4), pp. 825-828, 2009.
Abstract | Links | BibTeX | Tags: nanorod, ZnO
@article{2009kitamuraAPB,
title = {Observation of quantum confinement in ZnO nanorods fabricated using a two-temperature growth method},
author = {Kokoro Kitamura and Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1007/s00340-009-3654-1},
year = {2009},
date = {2009-12-01},
journal = {Applied Physics B},
volume = {97},
number = {4},
pages = {825-828},
publisher = {Springer Nature},
abstract = {We observed a quantum confinement effect in vertically well-aligned ultrafine ZnO nanorods using polarized excitation photoluminescence measurements. Room-temperature and low-temperature photoluminescence spectra revealed that free excitons were confined in the nanorods. The magnitude of the energy shift due to the quantum confinement in the ultrafine ZnO nanorods was 6 meV at room temperature, which corresponded to the luminescence from ZnO nanorods 12.8 nm in diameter. The diameter estimated from the spectra was comparable to the value measured from SEM images.},
keywords = {nanorod, ZnO},
pubstate = {published},
tppubtype = {article}
}
We observed a quantum confinement effect in vertically well-aligned ultrafine ZnO nanorods using polarized excitation photoluminescence measurements. Room-temperature and low-temperature photoluminescence spectra revealed that free excitons were confined in the nanorods. The magnitude of the energy shift due to the quantum confinement in the ultrafine ZnO nanorods was 6 meV at room temperature, which corresponded to the luminescence from ZnO nanorods 12.8 nm in diameter. The diameter estimated from the spectra was comparable to the value measured from SEM images.
Takashi Yatsui, Suguru Sangu, Kiyoshi Kobayashi, Tadashi Kawazoe, Motoichi Ohtsu, Jinkyoung Yoo, Gyu-Chul Yi
Nanophotonic energy up conversion using ZnO nanorod double-quantum-well structures Journal Article
In: Applied Physics Letters, 94 (8), pp. 083113, 2009.
Abstract | Links | BibTeX | Tags: First, nanorod, Non-uniform optical near field, ZnO
@article{doi:10.1063/1.3090491,
title = {Nanophotonic energy up conversion using ZnO nanorod double-quantum-well structures},
author = {Takashi Yatsui and Suguru Sangu and Kiyoshi Kobayashi and Tadashi Kawazoe and Motoichi Ohtsu and Jinkyoung Yoo and Gyu-Chul Yi},
url = {https://doi.org/10.1063/1.3090491},
doi = {10.1063/1.3090491},
year = {2009},
date = {2009-02-01},
journal = {Applied Physics Letters},
volume = {94},
number = {8},
pages = {083113},
abstract = {We report on near-field spectroscopy of ZnO/ZnMgO nanorod double-quantum-well structures (DQWs) for a nanometer-scale photonic device. We observed energy up conversion assisted by the absorption of phonons generated in the ZnO nanorod DQWs. Theoretical calculation of the coherent excitonic excitation of the population with incoherent phonon coupling agrees well with the obtained experimental power dependence of the up conversion efficiency. It should result in an increase in the efficiency of devices, such as photodetectors, solar cells, and so on.},
keywords = {First, nanorod, Non-uniform optical near field, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report on near-field spectroscopy of ZnO/ZnMgO nanorod double-quantum-well structures (DQWs) for a nanometer-scale photonic device. We observed energy up conversion assisted by the absorption of phonons generated in the ZnO nanorod DQWs. Theoretical calculation of the coherent excitonic excitation of the population with incoherent phonon coupling agrees well with the obtained experimental power dependence of the up conversion efficiency. It should result in an increase in the efficiency of devices, such as photodetectors, solar cells, and so on.
2008
Takashi Yatsui, Hyung Su Jeong, Motoichi Ohtsu
Controlling the energy transfer between near-field optically coupled ZnO quantum dots Journal Article
In: Applied Physics B, 93 (1), pp. 199-202, 2008.
Abstract | Links | BibTeX | Tags: Electrodes, First, QD, ZnO
@article{2008yatsuiAPBZnO,
title = {Controlling the energy transfer between near-field optically coupled ZnO quantum dots},
author = {Takashi Yatsui and Hyung Su Jeong and Motoichi Ohtsu},
doi = {10.1007/s00340-008-3154-8},
year = {2008},
date = {2008-10-01},
journal = {Applied Physics B},
volume = {93},
number = {1},
pages = {199-202},
publisher = {Springer Nature},
abstract = {We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was 144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled.},
keywords = {Electrodes, First, QD, ZnO},
pubstate = {published},
tppubtype = {article}
}
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was 144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled.
Kokoro Kitamura, Takashi Yatsui, Motoichi Ohtsu
Optical and Structural Properties of ZnO Nanorods Grown on Polyimide Films Journal Article
In: Applied Physics Express, 1 (8), pp. 081202, 2008.
Abstract | Links | BibTeX | Tags: nanorod, ZnO
@article{Kitamura_2008,
title = {Optical and Structural Properties of ZnO Nanorods Grown on Polyimide Films},
author = {Kokoro Kitamura and Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1143/apex.1.081202},
year = {2008},
date = {2008-08-01},
journal = {Applied Physics Express},
volume = {1},
number = {8},
pages = {081202},
publisher = {IOP Publishing},
abstract = {We report the direct growth of vertically well-aligned single-crystal ZnO nanorods on a polyimide film by low-temperature catalyst-free metal organic chemical vapor deposition at 450 °C. The polyimide film maintained its flexibility after the nanorods were grown. The growth direction of the nanorods was along the c-axis. They exhibited excellent photoluminescence characteristics. The spectral full-width at half-maximum measured at room temperature was found to be comparable to that of ZnO nanorods grown on sapphire substrate.},
keywords = {nanorod, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report the direct growth of vertically well-aligned single-crystal ZnO nanorods on a polyimide film by low-temperature catalyst-free metal organic chemical vapor deposition at 450 °C. The polyimide film maintained its flexibility after the nanorods were grown. The growth direction of the nanorods was along the c-axis. They exhibited excellent photoluminescence characteristics. The spectral full-width at half-maximum measured at room temperature was found to be comparable to that of ZnO nanorods grown on sapphire substrate.
Kokoro Kitamura, Takashi Yatsui, Motoichi Ohtsu, Gyu-Chul Yi
Fabrication of vertically aligned ultrafine ZnO nanorods using metal–organic vapor phase epitaxy with a two-temperature growth method Journal Article
In: Nanotechnology, 19 (17), pp. 175305, 2008.
Abstract | Links | BibTeX | Tags: nanorod, ZnO
@article{Kitamura_2008b,
title = {Fabrication of vertically aligned ultrafine ZnO nanorods using metal–organic vapor phase epitaxy with a two-temperature growth method},
author = {Kokoro Kitamura and Takashi Yatsui and Motoichi Ohtsu and Gyu-Chul Yi},
doi = {10.1088/0957-4484/19/17/175305},
year = {2008},
date = {2008-03-01},
journal = {Nanotechnology},
volume = {19},
number = {17},
pages = {175305},
publisher = {IOP Publishing},
abstract = {We report the fabrication of vertically aligned ultrafine ZnO nanorods using metal–organic
vapor phase epitaxy and applying a two-temperature growth method. First, thick nanorods
were grown vertically on the substrate at a lower temperature. Then, ultrafine ZnO
nanorods with an average diameter of 17.7 nm were grown from the tips of the thick
nanorods at a higher temperature. The direction of the ultrafine ZnO nanorods followed
that of the preformed vertically aligned thick nanorods. Electron microscopy revealed that
the ultrafine nanorods were single crystals and the growth direction was along the
c
axis. Excellent photoluminescence characteristics of the nanorods were confirmed.},
keywords = {nanorod, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report the fabrication of vertically aligned ultrafine ZnO nanorods using metal–organic
vapor phase epitaxy and applying a two-temperature growth method. First, thick nanorods
were grown vertically on the substrate at a lower temperature. Then, ultrafine ZnO
nanorods with an average diameter of 17.7 nm were grown from the tips of the thick
nanorods at a higher temperature. The direction of the ultrafine ZnO nanorods followed
that of the preformed vertically aligned thick nanorods. Electron microscopy revealed that
the ultrafine nanorods were single crystals and the growth direction was along the
c
axis. Excellent photoluminescence characteristics of the nanorods were confirmed.
vapor phase epitaxy and applying a two-temperature growth method. First, thick nanorods
were grown vertically on the substrate at a lower temperature. Then, ultrafine ZnO
nanorods with an average diameter of 17.7 nm were grown from the tips of the thick
nanorods at a higher temperature. The direction of the ultrafine ZnO nanorods followed
that of the preformed vertically aligned thick nanorods. Electron microscopy revealed that
the ultrafine nanorods were single crystals and the growth direction was along the
c
axis. Excellent photoluminescence characteristics of the nanorods were confirmed.
2007
Takashi Yatsui, Jungshik Lim, Tooru Nakamata, Kokoro Kitamura, Motoichi Ohtsu, Gyu-Chul Yi
Low-temperature (~270 oC) growth of vertically aligned ZnO nanorods using photoinduced metal organic vapour phase epitaxy Journal Article
In: Nanotechnology, 18 (6), pp. 065606, 2007.
Abstract | Links | BibTeX | Tags: First, nanorod, Near-field effect, ZnO
@article{Yatsui_2007,
title = {Low-temperature (~270 oC) growth of vertically aligned ZnO nanorods using photoinduced metal organic vapour phase epitaxy},
author = {Takashi Yatsui and Jungshik Lim and Tooru Nakamata and Kokoro Kitamura and Motoichi Ohtsu and Gyu-Chul Yi},
doi = {10.1088/0957-4484/18/6/065606},
year = {2007},
date = {2007-02-01},
journal = {Nanotechnology},
volume = {18},
number = {6},
pages = {065606},
publisher = {IOP Publishing},
abstract = {We successfully produced a drastic decrease in the required growth temperature
of single-crystalline ZnO nanorods, and enabled successful growth of vertically
aligned ZnO nanorods on a Si(100) substrate using photoinduced metal organic
vapour phase epitaxy (MOVPE). We introduced 325 nm light during the MOVPE
growth, and achieved vertical growth of single-crystalline ZnO nanorods
with a hexagonal crystal structure on Si(100) at a growth temperature of
270 °C. The successful low-temperature growth of ZnO nanorods on the Si(100) substrate
described here is a promising step toward designing nanoscale photonic and electronic
devices required by future systems.},
keywords = {First, nanorod, Near-field effect, ZnO},
pubstate = {published},
tppubtype = {article}
}
We successfully produced a drastic decrease in the required growth temperature
of single-crystalline ZnO nanorods, and enabled successful growth of vertically
aligned ZnO nanorods on a Si(100) substrate using photoinduced metal organic
vapour phase epitaxy (MOVPE). We introduced 325 nm light during the MOVPE
growth, and achieved vertical growth of single-crystalline ZnO nanorods
with a hexagonal crystal structure on Si(100) at a growth temperature of
270 °C. The successful low-temperature growth of ZnO nanorods on the Si(100) substrate
described here is a promising step toward designing nanoscale photonic and electronic
devices required by future systems.
of single-crystalline ZnO nanorods, and enabled successful growth of vertically
aligned ZnO nanorods on a Si(100) substrate using photoinduced metal organic
vapour phase epitaxy (MOVPE). We introduced 325 nm light during the MOVPE
growth, and achieved vertical growth of single-crystalline ZnO nanorods
with a hexagonal crystal structure on Si(100) at a growth temperature of
270 °C. The successful low-temperature growth of ZnO nanorods on the Si(100) substrate
described here is a promising step toward designing nanoscale photonic and electronic
devices required by future systems.
Takashi Yatsui, Suguru Sangu, Tadashi Kawazoe, Motoichi Ohtsu, Sung Jin An, Jinkyoung Yoo, Gyu-Chul Yi
Nanophotonic switch using ZnO nanorod double-quantum-well structures Journal Article
In: Applied Physics Letters, 90 (22), pp. 223110, 2007.
Abstract | Links | BibTeX | Tags: First, Nanophotonic device, Selected, ZnO
@article{doi:10.1063/1.2743949,
title = {Nanophotonic switch using ZnO nanorod double-quantum-well structures},
author = {Takashi Yatsui and Suguru Sangu and Tadashi Kawazoe and Motoichi Ohtsu and Sung Jin An and Jinkyoung Yoo and Gyu-Chul Yi},
doi = {10.1063/1.2743949},
year = {2007},
date = {2007-01-01},
journal = {Applied Physics Letters},
volume = {90},
number = {22},
pages = {223110},
abstract = {The authors report on time-resolved near-field spectroscopy of ZnO∕ZnMgO nanorod double-quantum-well structures (DQWs) for a nanometer-scale photonic device. They observed nutation of the population between the resonantly coupled exciton states of DQWs. Furthermore, they demonstrated switching dynamics by controlling the exciton excitation in the dipole-inactive state via an optical near field. The results of time-resolved near-field spectroscopy of isolated DQWs described here are a promising step toward designing a nanometer-scale photonic switch and related devices.},
keywords = {First, Nanophotonic device, Selected, ZnO},
pubstate = {published},
tppubtype = {article}
}
The authors report on time-resolved near-field spectroscopy of ZnO∕ZnMgO nanorod double-quantum-well structures (DQWs) for a nanometer-scale photonic device. They observed nutation of the population between the resonantly coupled exciton states of DQWs. Furthermore, they demonstrated switching dynamics by controlling the exciton excitation in the dipole-inactive state via an optical near field. The results of time-resolved near-field spectroscopy of isolated DQWs described here are a promising step toward designing a nanometer-scale photonic switch and related devices.
2006
Takashi Yatsui, Motoichi Ohtsu, Sung Jin An, Jinkyoung Yoo, Gyu-Chul Yi
In: Optical Review, 13 (4), pp. 218-221, 2006.
Abstract | Links | BibTeX | Tags: First, nanorod, Near-field spectroscopy, ZnO
@article{2006yatsuiOptRev,
title = {Evaluating the quantum confinement effect of isolated ZnO nanorod single-quantum-well structures using near-field ultraviolet photoluminescence spectroscopy},
author = {Takashi Yatsui and Motoichi Ohtsu and Sung Jin An and Jinkyoung Yoo and Gyu-Chul Yi},
doi = {10.1007/s10043-006-0218-z},
year = {2006},
date = {2006-07-01},
journal = {Optical Review},
volume = {13},
number = {4},
pages = {218-221},
publisher = {Springer Nature},
abstract = {Using low-temperature near-field spectroscopy, we obtained spatially and spectrally resolved photoluminescence (PL) images of individual ZnO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 20 nm. We observed the dependence of the quantum confinement effect of the PL peak on the well width (L aw), from which the linewidths of near-field PL spectra of ZnO nanorod SQWs (L aw = 2.5 and 3.75 nm) were determined to be as narrow as 3 meV. However, near-field PL spectra of individual SQWs with L aw = 5.0 nm exhibited two PL peaks, presumably due to strains or defects in the ZnMgO in the nanorod SQWs. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices.},
keywords = {First, nanorod, Near-field spectroscopy, ZnO},
pubstate = {published},
tppubtype = {article}
}
Using low-temperature near-field spectroscopy, we obtained spatially and spectrally resolved photoluminescence (PL) images of individual ZnO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 20 nm. We observed the dependence of the quantum confinement effect of the PL peak on the well width (L aw), from which the linewidths of near-field PL spectra of ZnO nanorod SQWs (L aw = 2.5 and 3.75 nm) were determined to be as narrow as 3 meV. However, near-field PL spectra of individual SQWs with L aw = 5.0 nm exhibited two PL peaks, presumably due to strains or defects in the ZnMgO in the nanorod SQWs. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices.
Eue-Soon Jang, Jun Young Bae, Jinkyoung Yoo, Won Il Park, Dong-Wook Kim, Gyu-Chul Yi, Takashi Yatsui, Motoichi Ohtsu
Quantum confinement effect in ZnO/Mg0.2Zn0.8O multishell nanorod heterostructures Journal Article
In: Applied Physics Letters, 88 (2), pp. 023102, 2006.
Abstract | Links | BibTeX | Tags: MQW, Near-field spectroscopy, ZnO
@article{doi:10.1063/1.2162695,
title = {Quantum confinement effect in ZnO/Mg0.2Zn0.8O multishell nanorod heterostructures},
author = {Eue-Soon Jang and Jun Young Bae and Jinkyoung Yoo and Won Il Park and Dong-Wook Kim and Gyu-Chul Yi and Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1063/1.2162695},
year = {2006},
date = {2006-01-01},
journal = {Applied Physics Letters},
volume = {88},
number = {2},
pages = {023102},
abstract = {We report on photoluminescence measurements of Mg0.2Zn0.8O/ZnO/Mg0.2Zn0.8O multishell layers on ZnO core nanorods. Dominant excitonic emissions in the photoluminescence spectra show a blueshift depending on the ZnO shell layer thickness attributed to the quantum confinement effect in the nanorod heterostructure radial direction. Furthermore, near-field scanning optical microscopy clearly shows sharp photoluminescence peaks from the individual nanorod quantum structures, corresponding to subband levels.},
keywords = {MQW, Near-field spectroscopy, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report on photoluminescence measurements of Mg0.2Zn0.8O/ZnO/Mg0.2Zn0.8O multishell layers on ZnO core nanorods. Dominant excitonic emissions in the photoluminescence spectra show a blueshift depending on the ZnO shell layer thickness attributed to the quantum confinement effect in the nanorod heterostructure radial direction. Furthermore, near-field scanning optical microscopy clearly shows sharp photoluminescence peaks from the individual nanorod quantum structures, corresponding to subband levels.
2005
Takashi Yatsui, Motoichi Ohtsu, Jinkyoung Yoo, Sung Jin An, Gyu-Chul Yi
Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures Journal Article
In: Applied Physics Letters, 87 (3), pp. 033101, 2005.
Abstract | Links | BibTeX | Tags: First, Near-field spectroscopy, QW, ZnO
@article{doi:10.1063/1.1990247,
title = {Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures},
author = {Takashi Yatsui and Motoichi Ohtsu and Jinkyoung Yoo and Sung Jin An and Gyu-Chul Yi},
doi = {10.1063/1.1990247},
year = {2005},
date = {2005-07-01},
journal = {Applied Physics Letters},
volume = {87},
number = {3},
pages = {033101},
abstract = {We report low-temperature near-field spectroscopy of isolated ZnO∕ZnMgO single-quantum-well structures (SQWs) on the end of ZnO nanorod to define their potential for nanophotonics. First, absorption spectra of isolated ZnO∕ZnMgO nanorod SQWs with the Stokes shift as small as 3meV and very sharp photoluminescent peaks indicate that the nanorod SQWs are of very high optical quality. Furthermore, we performed polarization spectroscopy of isolated ZnO SQWs, and observed valence-band anisotropy of ZnO SQWs in photoluminescence spectra directly. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices.},
keywords = {First, Near-field spectroscopy, QW, ZnO},
pubstate = {published},
tppubtype = {article}
}
We report low-temperature near-field spectroscopy of isolated ZnO∕ZnMgO single-quantum-well structures (SQWs) on the end of ZnO nanorod to define their potential for nanophotonics. First, absorption spectra of isolated ZnO∕ZnMgO nanorod SQWs with the Stokes shift as small as 3meV and very sharp photoluminescent peaks indicate that the nanorod SQWs are of very high optical quality. Furthermore, we performed polarization spectroscopy of isolated ZnO SQWs, and observed valence-band anisotropy of ZnO SQWs in photoluminescence spectra directly. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices.
2004
Takashi Yatsui, Jungshik Lim, Motoichi Ohtsu, Sung Jin An, Gyu-Chul Yi
In: Applied Physics Letters, 85 (5), pp. 727-729, 2004.
Abstract | Links | BibTeX | Tags: First, nanorod, Near-field spectroscopy, QW, ZnO
@article{doi:10.1063/1.1776338,
title = {Evaluation of the discrete energy levels of individual ZnO nanorodsingle-quantum-well structures using near-field ultraviolet photoluminescence spectroscopy},
author = {Takashi Yatsui and Jungshik Lim and Motoichi Ohtsu and Sung Jin An and Gyu-Chul Yi},
doi = {10.1063/1.1776338},
year = {2004},
date = {2004-08-01},
journal = {Applied Physics Letters},
volume = {85},
number = {5},
pages = {727-729},
abstract = {Spatially and spectrally resolved photoluminescence imaging of individual ZnO∕ZnMgO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 55nm was performed using the optical near-field technique with a metallized UV fiber probe. Using excitation power density-dependent photoluminescence spectra of a ZnO∕ZnMgO SQW nanorod, we observed the discrete energy levels in a ZnO quantum-well layer.},
keywords = {First, nanorod, Near-field spectroscopy, QW, ZnO},
pubstate = {published},
tppubtype = {article}
}
Spatially and spectrally resolved photoluminescence imaging of individual ZnO∕ZnMgO nanorod single-quantum-well structures (SQWs) with a spatial resolution of 55nm was performed using the optical near-field technique with a metallized UV fiber probe. Using excitation power density-dependent photoluminescence spectra of a ZnO∕ZnMgO SQW nanorod, we observed the discrete energy levels in a ZnO quantum-well layer.
2003
Tae-Won Kim, Tadashi Kawazoe, Shunsuke Yamazaki, Jungshik Lim, Takashi Yatsui, Motoichi Ohtsu
Room temperature ultraviolet emission from ZnO nanocrystallites fabricated by the low temperature oxidation of metallic Zn precursors Journal Article
In: Solid State Communications, 127 (1), pp. 21 - 24, 2003, ISSN: 0038-1098.
Abstract | Links | BibTeX | Tags: ZnO
@article{KIM200321,
title = {Room temperature ultraviolet emission from ZnO nanocrystallites fabricated by the low temperature oxidation of metallic Zn precursors},
author = {Tae-Won Kim and Tadashi Kawazoe and Shunsuke Yamazaki and Jungshik Lim and Takashi Yatsui and Motoichi Ohtsu},
doi = {10.1016/S0038-1098(03)00346-6},
issn = {0038-1098},
year = {2003},
date = {2003-04-01},
journal = {Solid State Communications},
volume = {127},
number = {1},
pages = {21 - 24},
abstract = {We have successfully fabricated ZnO nanocrystallites emitting strong ultraviolet radiation at room temperature via the simple thermal oxidation of metallic Zn precursors at 380 °C. X-ray diffraction measurements showed only the diffraction peak from ZnO, revealing that metallic Zn precursors were successfully oxidized even at the low temperature of 380 °C. The mean size of the ZnO nanocrystallites determined using Scherrer's formula was ca. 30 nm. Room temperature photoluminescence measurements using a cw He–Cd laser (λ=325nm) showed a strong emission peak at 3.27eV, which was ascribed to free excition recombination. These results suggest that sufficient oxygen can diffuse into the metallic Zn precursors, even at temperatures as low as 380 °C, to allow the fabrication of pure ZnO nanocrystallites.},
keywords = {ZnO},
pubstate = {published},
tppubtype = {article}
}
We have successfully fabricated ZnO nanocrystallites emitting strong ultraviolet radiation at room temperature via the simple thermal oxidation of metallic Zn precursors at 380 °C. X-ray diffraction measurements showed only the diffraction peak from ZnO, revealing that metallic Zn precursors were successfully oxidized even at the low temperature of 380 °C. The mean size of the ZnO nanocrystallites determined using Scherrer's formula was ca. 30 nm. Room temperature photoluminescence measurements using a cw He–Cd laser (λ=325nm) showed a strong emission peak at 3.27eV, which was ascribed to free excition recombination. These results suggest that sufficient oxygen can diffuse into the metallic Zn precursors, even at temperatures as low as 380 °C, to allow the fabrication of pure ZnO nanocrystallites.
2002
Takashi Yatsui, Tadashi Kawazoe, Takashi Shimizu, Yoh Yamamoto, Minoru Ueda, Motonobu Kourogi, Motoichi Ohtsu, Geun-Hyoung Lee
Observation of size-dependent features in the photoluminescence of zinc oxide nanocrystallites by near-field ultraviolet spectroscopy Journal Article
In: Applied Physics Letters, 80 (8), pp. 1444-1446, 2002.
Abstract | Links | BibTeX | Tags: First, Near-field spectroscopy, ZnO
@article{doi:10.1063/1.1453487,
title = {Observation of size-dependent features in the photoluminescence of zinc oxide nanocrystallites by near-field ultraviolet spectroscopy},
author = {Takashi Yatsui and Tadashi Kawazoe and Takashi Shimizu and Yoh Yamamoto and Minoru Ueda and Motonobu Kourogi and Motoichi Ohtsu and Geun-Hyoung Lee},
doi = {10.1063/1.1453487},
year = {2002},
date = {2002-01-01},
journal = {Applied Physics Letters},
volume = {80},
number = {8},
pages = {1444-1446},
abstract = {The optical properties of single zinc oxide (ZnO) nanocrystallites were investigated at room temperature by extending the optical near-field technique to the UV region. Using a UV fiber probe with a subwavelength aperture, we performed spatially- and spectrally-resolved photoluminescence (PL) imaging of individual ZnO nanocrystallites with a spatial resolution of 55 nm. Furthermore, decreasing the spot size increased the intensities of higher-energy components of the PL spectrum due to the quantum size effect.},
keywords = {First, Near-field spectroscopy, ZnO},
pubstate = {published},
tppubtype = {article}
}
The optical properties of single zinc oxide (ZnO) nanocrystallites were investigated at room temperature by extending the optical near-field technique to the UV region. Using a UV fiber probe with a subwavelength aperture, we performed spatially- and spectrally-resolved photoluminescence (PL) imaging of individual ZnO nanocrystallites with a spatial resolution of 55 nm. Furthermore, decreasing the spot size increased the intensities of higher-energy components of the PL spectrum due to the quantum size effect.
2001
Takashi Yatsui, Takashi Shimizu, Yoh Yamamoto, Motonobu Kourogi, Motoichi Ohtsu, Geun-Hyoung Lee
Near-field ultraviolet photoluminescence spectroscopy for evaluating the crystallinity of polycrystalline zinc oxide Journal Article
In: Applied Physics Letters, 79 (15), pp. 2369-2371, 2001.
Abstract | Links | BibTeX | Tags: First, Near-field spectroscopy, ZnO
@article{doi:10.1063/1.1410357,
title = {Near-field ultraviolet photoluminescence spectroscopy for evaluating the crystallinity of polycrystalline zinc oxide},
author = {Takashi Yatsui and Takashi Shimizu and Yoh Yamamoto and Motonobu Kourogi and Motoichi Ohtsu and Geun-Hyoung Lee},
doi = {10.1063/1.1410357},
year = {2001},
date = {2001-10-01},
journal = {Applied Physics Letters},
volume = {79},
number = {15},
pages = {2369-2371},
abstract = {By extending the optical near-field technique to the ultraviolet region, a two-dimensional evaluation of the optical properties and crystallinity of polycrystalline zinc oxide (ZnO) was carried out at room temperature. Using an ultraviolet fiber probe with an aperture diameter of 80 nm, we obtained spatially resolved photoluminescence spectra from individual ZnO nanocrystallites; the emission intensity depended on the topography and on crystal orientation.},
keywords = {First, Near-field spectroscopy, ZnO},
pubstate = {published},
tppubtype = {article}
}
By extending the optical near-field technique to the ultraviolet region, a two-dimensional evaluation of the optical properties and crystallinity of polycrystalline zinc oxide (ZnO) was carried out at room temperature. Using an ultraviolet fiber probe with an aperture diameter of 80 nm, we obtained spatially resolved photoluminescence spectra from individual ZnO nanocrystallites; the emission intensity depended on the topography and on crystal orientation.