Papers - Koji Asaka

Ultrahigh porosity photoluminescent silicon aerocrystals with greater than 50% nanocrystal ensemble quantum yields Reviewed

Bernard Gelloz, Leigh Canham, Koji Asaka, Yuto Nakamura, and Hideo Kishida

Journal of Applied Physics   134   033103   2023

Self-organized Ge_1−xSn_x quantum dots formed on insulators and their room temperature photoluminescence Reviewed

Kaoru Hashimoto, Shigehisa Shibayama, Koji Asaka, Mitsuo Sakashita, Masashi Kurosawa, and Osamu Nakatsuka

Japanese Journal of Applied Physics   62   075506   2023

Solid-phase crystallization of ultra-thin amorphous Ge layers on insulators Reviewed

Ryo Oishi, Koji Asaka, Leonid Bolotov, Noriyuki Uchida, Masashi Kurosawa, and Osamu Nakatsuka

Japanese Journal of Applied Physics   61   SC1086   2022

Critical current density for layer-by-layer breakdown of a multiwall carbon nanotube Reviewed

Koji Asaka, Kentaro Yamauchi, and Yahachi Saito

Diamond and Related Materials   124   108907   2022

　More details

Electric-current-induced structural changes in a suspended multiwall carbon nanotube (MWCNT) were observed through in-situ transmission electron microscopy. The bias voltage and electric current were measured simultaneously as the MWCNT was imaged. The passage of excessive current led to breakdown of the surface of the MWCNT and to subsequent layer-by-layer removal of the broken outermost shell via sublimation of carbon atoms. The surface breakdown of the MWCNT was accompanied by a discrete decrease in the current. Under the assumption that the current passes solely through the outermost shell of the MWCNT, we found that the critical current densities at which the breakdown in the renewed outermost shell occurred after the removal of the broken outermost shell were limited to a remarkably narrow range of (2.4 ± 0.2)×10⁹ A/cm², irrespective of the outermost diameter of the MWCNT. The present results provide invaluable information about electron transport phenomena in MWCNTs and about the durability of CNT nanocircuits.

Impact of wet annealing on ferroelectric phase formation and phase transition of HfO2-ZrO2 system Reviewed

Shigehisa Shibayama, Jotaro Nagano, Koji Asaka, Mitsuo Sakashita, and Osamu Nakatsuka

ACS Applied Electronic Materials   3   2203 - 2211   2021

Hole doping in polythiophenes encapsulated in semiconducting and metallic single-walled carbon nanotubes: Impact of the electronic structure Reviewed

Hiroto Kageyama, Koji Asaka, Hideo Kishida, and Takeshi Koyama

Macromolecules   54   11147 - 11153   2021

Light emission and structural changes in a suspended multiwall carbon nanotube on application of electric current Reviewed

Koji Asaka, Koshi Nishikawa, and Yahachi Saito

Diamond and Related Materials   111   108175   2021

Raman spectroscopy and TEM of long linear carbon chain formed in CNT field emission cathode Reviewed

Koji Asaka, Satoshi Toma, and Yahachi Saito

e-Journal of Surface Science and Nanotechnology   18   159 - 163   2020

Excitation energy transfer by electron exchange via two-step electron transfer between single-walled carbon nanotube and encapsulated magnesium porphyrin Reviewed

Takeshi Koyama, Junpei Sugiura, Tomonari Koishi, Ryosuke Ohashi, Koji Asaka, Takeshi Saito, Yanlin Gao, Susumu Okada, and Hideo Kishida

The Journal of Physical Chemistry C   124   19406 - 19412   2020

Application of multiwall carbon nanotubes to conductive manipulation-probe tips for in-situ transmission electron microscopy of nanometer-sized material: Electrical measurement of a silicon nanoparticle Reviewed

Koji Asaka, Tomohiro Terada, and Yahachi Saito

Materials Research Express   6   015038-1-5   2019

Raman spectroscopy and transmission electron microscopy study on long linear atomic carbon chains generated by field electron emission accompanied with electrical discharge of carbon nanotube films Reviewed

Koji Asaka, Satoshi Toma, and Yahachi Saito

SN Applied Sciences   1   493   2019

Si/SiO2 core/shell luminescent silicon nanocrystals and porous silicon powders with high quantum yield, long lifetime and good stability Reviewed

Bernard Gelloz, Firman Bagja Juangs, Tomohiro Nozaki, Koji Asaka, Nobuyoshi Koshida, and Lianhua Jin

Frontiers in Physics   7   47-1-7   2019

Bulk synthesis of linear carbon-chains confined inside single-wall carbon nanotubes by vacuum discharge Reviewed

Satoshi Toma, Koji Asaka, Masaru Irita, and Yahachi Saito

Surface and Interface Analysis   51   131 - 135   2019

Different molecular arrangement of perylene in metallic and semiconducting carbon nanotubes: Impact of van der Waals interaction Reviewed

Takeshi Koyama, Kazuma Fujiki, Yuya Nagasawa, Susumu Okada, Koji Asaka, Yahachi Saito, and Hideo Kishida

The Journal of Physical Chemistry C   122   5805 - 5812   2018

High-temperature reaction of amorphous silicon with carbon on a multiwall carbon nanotube heater and temperature measurement by thermal radiation spectra Reviewed

Koji Asaka, Tomohiro Terada, and Yahachi Saito

Journal of Materials Science   52   7232 - 7238   2017

In-situ TEM study on structural change and light emission of a multiwall carbon nanotube during Joule heating Reviewed

Koshi Nishikawa, Koji Asaka, Hitoshi Nakahara, and Yahachi Saito

IOP Conference Series: Materials Science and Engineering   304   012011   2017

Facile synthetic route to atomically thin conductive wires from single-species molecules in one-dimensionally confined space: Doped conjugated polymers inside single-walled carbon nanotubes Reviewed

Makoto Sasaki, Takeshi Koyama, Hideo Kishida, Koji Asaka, Yahachi Saito, Yukihiro Yoshida, and Gunzi Saito

The Journal of Physical Chemistry Letters   8   1702 - 1706   2017

Ultrafast excitation energy transfer from encapsulated quaterrylene to single-walled carbon nanotube Reviewed

Takeshi Koyama, Takuya Tsunekawa, Takeshi Saito, Koji Asaka, Yahachi Saito, Hideo Kishida, and Arao Nakamura

Journal of Luminescence   169   645 - 648   2016

Spontaneous graphenization of amorphous carbon on clean surfaces of nanometer-sized nickel particles at room temperature Reviewed

Koji Asaka and Yahachi Saito

Carbon   103   352 - 355   2016

Field emission patterns showing symmetry of electronic states in graphene edges Reviewed

Noboru Yokoyama, Kazuya Nakakubo, Kohji Iwata, Koji Asaka, Hitoshi Nakahara, and Yahachi Saito

Surface and Interface Analysis   48   1217 - 1220   2016