Guozhu Zhang
Kyushu University
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Publication
Featured researches published by Guozhu Zhang.
Nano Letters | 2017
Hiroshi Anzai; Masaru Suzuki; Kazuki Nagashima; Masaki Kanai; Zetao Zhu; Yong He; Mickaël Boudot; Guozhu Zhang; Tsunaki Takahashi; Katsuichi Kanemoto; Takehito Seki; Naoya Shibata; Takeshi Yanagida
Single crystalline nanowires composed of semiconducting metal oxides formed via a vapor-liquid-solid (VLS) process exhibit an electrical conductivity even without an intentional carrier doping, although these stoichiometric metal oxides are ideally insulators. Suppressing this unintentional doping effect has been a challenging issue not only for metal oxide nanowires but also for various nanostructured metal oxides toward their semiconductor applications. Here we demonstrate that a pure VLS crystal growth, which occurs only at liquid-solid (LS) interface, substantially suppresses an unintentional doping of single crystalline SnO2 nanowires. By strictly tailoring the crystal growth interface of VLS process, we found the gigantic difference of electrical conduction (up to 7 orders of magnitude) between nanowires formed only at LS interface and those formed at both LS and vapor-solid (VS) interfaces. On the basis of investigations with spatially resolved single nanowire electrical measurements, plane-view electron energy-loss spectroscopy, and molecular dynamics simulations, we reveal the gigantic suppression of unintentional carrier doping only for the crystal grown at LS interface due to the higher annealing effect at LS interface compared with that grown at VS interface. These implications will be a foundation to design the semiconducting properties of various nanostructured metal oxides.
ACS Sensors | 2017
Hao Zeng; Tsunaki Takahashi; Masaki Kanai; Guozhu Zhang; Yong He; Kazuki Nagashima; Takeshi Yanagida
Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO2 (ATO) contacts on SnO2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO2 nanowire sensors while maintaining the sensitivity for both NO2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.
The Japan Society of Applied Physics | 2018
Tsunaki Takahashi; Hao Zeng; Kentaro Nakamura; Masaki Kanai; Guozhu Zhang; Kazuki Nagashima; Takeshi Yanagida
The Japan Society of Applied Physics | 2018
Kazuki Nagashima; Hirotaka Koga; Guozhu Zhang; Akihide Inoue; Masaya Nogi; Takeshi Yanagida
The Japan Society of Applied Physics | 2018
Hiroki Yamashita; Kazuki Nagashima; Daiki Sakai; Tsunaki Takahashi; Guozhu Zhang; Masaki Kanai; Takeshi Yanagida
The Japan Society of Applied Physics | 2018
Hiroshi Anzai; Tsunaki Takahashi; Guozhu Zhang; Masaki Kanai; Kazuki Nagashima; Takeshi Yanagida
The Japan Society of Applied Physics | 2017
Hiroshi Anzai; Kazuki Nagashima; Masaru Suzuki; Zetao Zhu; Masaki Kanai; Yong He; Guozhu Zhang; Katsuichi Kanemoto; Takehito Seki; Naoya Shibata; Takeshi Yanagida
The Japan Society of Applied Physics | 2017
He Yong; Kazuki Nagashima; Chuanjun Liu; Tsunaki Takahashi; Guozhu Zhang; Rui Yatabe; Masaki Kanai; Kiyoshi Toko; Takeshi Yanagida
The Japan Society of Applied Physics | 2017
Yong He; Kazuki Nagashima; Tsunaki Takahashi; Guozhu Zhang; Masaki Kanai; Jun Terao; Ken Uchida; Takeshi Yanagida
The Japan Society of Applied Physics | 2017
Daiki Sakai; Kazuki Nagashima; Guozhu Zhang; Yong He; Akihide Inoue; Chie Nakamura; Masaki Kanai; Takeshi Yanagida