Browsing by Author "Chu, Fu-Hsuan"

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Direct observation of melting behaviors at the nanoscale under electron beam and heat to form hollow nanostructures
(2012)
Huang, Chun-Wei
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Hsin, Cheng-Lun
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Wang, Chun-Wen
;
Chu, Fu-Hsuan
;
Kao, Chen-Yen
"We report the melting behaviours of ZnO nanowire by heating ZnO-Al2O3 core-shell heterostructures to form Al2O3 nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al2O3 core-shell nanowire heterostructures were annealed at 600 degrees C under electron irradiation, the amorphous Al2O3 shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s(-1). The thickness of the Al2O3 nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al2O3 nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM)."
Electron Field Emission Properties of Nanomaterials on Rough Silicon Rods
(2010-01-14)
Wu, Hung-Chi
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Tsai, Tsung-Yen
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Chu, Fu-Hsuan
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Tai, Nyan-Hwa
;
Lin, Heh-Nan
Highly porous, individually separated, and vertically aligned rough silicon rods (r-SiRs) were formed via a modified electroless metal deposition (EMD) approach. Despite inheriting the length of crowded silicon nanowires (NWs) obtained by the conventionally adopted EMD method, the r-SiRs are distributed sparsely, subsequently forming an excellent field emitter substrate. The electron field emission (EFE) of carbon nanotubes (CNTs) grown on r-SiRs can be turned on at (E(0))(CNTs/r-SiRs) = 2.3 V/mu m, yielding a high EFE current density, (J(c))(CNTs/r-SiR) = 3.7 mA/cm(2) in an applied field of 5.1 V/mu m, Additionally, a cactuslike structure consisting of zinc oxide NWs on r-SiRs can be turned on at 2.9 V/mu m. The absence of a high-temperature or expensive photolithographic process makes r-SiRs a promising alternative as a silicon base field emitter substrate.
In Situ TEM and Energy Dispersion Spectrometer Analysis of Chemical Composition Change in ZnO Nanowire Resistive Memories
(2013-04-16)
Huang, Yu-Ting
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Yu, Shih-Ying
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Hsin, Cheng-Lun
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Huang, Chun-Wei
;
Kang, Chen-Fang
Resistive random-access memory (ReRAM) has been of wide interest for its potential to replace flash memory in the next-generation nonvolatile memory roadmap. In this study, we have fabricated the Au/ZnO-nanowire/Au nanomemory device by electron beam lithography and, subsequently, utilized in situ transmission electron microscopy (TEM) to observe the atomic structure evolution from the initial state to the low-resistance state (LRS) in the ZnO nanowire. The element mapping of LRS showing that the nanowire was zinc dominant indicating that the oxygen vacancies were introduced after resistance switching. The results provided direct evidence, suggesting that the resistance change resulted from oxygen migration.
Well-aligned ZnO nanowires with excellent field emission and photocatalytic properties
(2012)
Chu, Fu-Hsuan
;
Huang, Chun-Wei
;
Hsin, Cheng-Lun
;
Wang, Chun-Wen
;
Yu, Shih-Ying
Well-aligned ZnO nanowires (NWs) were successfully synthesized on Si(100) by the process of carbothermal reduction and vapor-liquid-solid method. Scanning electron microscopy and transmission electron microscopy results confirmed that ZnO NWs were single crystalline wurtzite structures and grew along the [0001] direction. The influences of substrate temperature and total pressure on the growth were discussed. The well-aligned ZnO NWs show good field emission properties, and the emitter constructed of pencil-like ZnO NWs exhibited a low turn-on field (3.82 V mu m(-1)) and a high field enhancement factor (beta 2303). Finally, we demonstrated that the as-prepared ZnO NWs with small diameter on the substrate have good photocatalytic activity toward degradation of methylene blue. Using ZnO NWs with Au nanoparticles (NPs) would decrease the recombination rate of hole-electron pairs due to the great shift of the Fermi level to the conduction band. Hence, adding Au NPs was a promising method to enhance the photocatalytic performance of ZnO NWs. It is significant that photocatalyst fabricated by ZnO NWs can apply to the degradation of organic pollution, and solve the environmental issues.