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Hwangyou Oh,Ju-Jin Kim,이정오,김상섭,Yeong-Sup Lo 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.5
We fabricated field effect transistors by using high quality single-crystalline ZnO nanowires and studied their electrical properties by gas adsorption. We measured the changes in the electrical properties due to the surface absorbed OH or O$_2$ from the ambient air. A rapid change in the threshold voltage of the gate response curve in the high vacuum region has been reproducibly observed. This change suggests that the adsorption mechanism may be different in the low and the high vacuum regions. By introducing reactive gas molecules to the surface of the nanowire channel in the high vacuum condition \textit{via} a mass flow controller, we could tune the number of carriers. We then obtained optimally-doped devices from the heavily-doped ones. We also developed an \textit{effective} surface cleansing procedure to enrich the electrical properties of pristine devices significantly by the introducing high-purity O$_2$ gas under high vacuum conditions.
Influence of Surface Morphology on Adsorption Behavior in ZnO Nanowire Field-Effect Transistors
Hwangyou Oh,이정오,김상섭,김주진 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
We fabricated field-effect transistors (FETs) using ZnO nanowires with different structures and studied the effect of the adsorption of gas molecules on the electrical properties of the obtained nanowire devices. Although they were grown on the same substrate and under the same synthesis conditions, the devices showed completely different adsorption behaviors, depending on their surface structures. Some FETs underwent oxidative adsorption reactions whereas others underwent reductive adsorption in ambient air. In addition to these differences in adsorption behavior, our experimental results show that the electron mobilities in the ZnO nanowire devices are also closely related to their surface structure.
Influence of Diameter on the Photoresponse in a Networked Zinc-Oxide Nanowire Photodetector
최헌진,Ryong Ha,변재철,Hwangyou Oh,최영진,박재관 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4
We report on the photoresponses of networked ZnO nanowire photodetectors fabricated by using a simple, mass-scalable process. ZnO nanowires were synthesized by using a carbothermal reduction process and the diameter of the nanowires was controlled by using the thickness of the gold catalyst. The photoresponse was measured by using photodectors fabricated with nanowires of 80 nm and 300 nm in diameter. The photoresponse showed no dependence on the diameter of the nanowires in the wavelength range of 200 ∽ 370 nm, which is attributed to the eects of photo-generation and photolysis on the surface nanowires, while it showed a dependence on the diameter in the wavelength range of 370 ∽ 650 nm.
The temperature-dependent electrical transport mechanism of single ZnO nanorods
Park, Jae Young,Oh, Hwangyou,Kim, Ju-Jin,Kim, Sang Sub IOP Pub 2006 Nanotechnology Vol.17 No.5
<P>The electrical transport properties of high quality ZnO nanorods, synthesized by catalyst-free metalorganic chemical vapour deposition, were studied as a function of temperature by fabricating field effect transistors based on single ZnO nanorods. The thermally activated Schottky emission was found to be a ruling transport mechanism in the temperature regime of 70–293 K over a wide range of electric fields with an effective barrier height of ∼120 meV. In contrast, the Fowler–Nordheim tunnelling dominated at low temperatures (<70 K) under very high electric fields.</P>
Platinum-Assisted Vapor-Liquid-Solid Growth of GaN Nanowires and Their Properties
오은순,Byoung Woo Lee,Sojung Shim,Ki-Young Lee,Hwangyou Oh,최헌진,손병희,Yeong Hwan Ahn 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Growth of GaN nanowires by using a vapor-liquid-solid (VLS) mechanism with Pt catalysts was investigated. Single-crystal GaN nanowires with diameters of ~100 nm and lengths of ~5 µm were grown with Pt and with the well-known VLS catalyst of Ni. The growth rate of nanowires with Pt was lower than that with Ni under identical processing conditions. Pt-Ga alloy globules were observed by Transmission electron microscopy at the ends of the nanowires which lead the growth by the VLS mechanism. Electrical data from individual nanowires indicated high conductivity associated with high electron concentration in the Pt-GaN nanowires.
Coupling of Semiconductor Nanowires with Neurons and Their Interfacial Structure
Lee, Ki-Young,Shim, Sojung,Kim, Il-Soo,Oh, Hwangyou,Kim, Sunoh,Ahn, Jae-Pyeong,Park, Seung-Han,Rhim, Hyewhon,Choi, Heon-Jin Springer 2010 NANOSCALE RESEARCH LETTERS Vol.5 No.2
<P>We report on the compatibility of various nanowires with hippocampal neurons and the structural study of the neuron–nanowire interface. Si, Ge, SiGe, and GaN nanowires are compatible with hippocampal neurons due to their native oxide, but ZnO nanowires are toxic to neuron due to a release of Zn ion. The interfaces of fixed Si nanowire and hippocampal neuron, cross-sectional samples, were prepared by focused ion beam and observed by transmission electron microscopy. The results showed that the processes of neuron were adhered well on the nanowire without cleft.</P>
Vertically Aligned Carbon-Nanotube Arrays Showing Schottky Behavior at Room Temperature
Jung, Seung-Ho,Jeong, Soo-Hwan,Kim, Sang-Uck,Hwang, Sun-Kyu,Lee, Pyung-Soo,Lee, Kun-Hong,Ko, Ju-Hye,Bae, Eunju,Kang, Donghun,Park, Wanjun,Oh, Hwangyou,Kim, Ju-Jin,Kim, Hyungseok,Park, Chan-Gyung WILEY-VCH Verlag 2005 Small Vol.1 No.5
<P>Vertically aligned carbon-nanotube (CNT) arrays were fabricated in the thin-film anodic aluminum oxide (AAO) templates on silicon wafers utilizing a niobium (Nb) thin film as the source electrode. The average diameter of the CNTs was 25 nm, and the number density was 3×10<SUP>10</SUP> cm<SUP>−2</SUP>. The CNT arrays synthesized at 700 °C and above exhibited Schottky behavior even at 300 K, with energy gaps between 0.2 eV and 0.3 eV. However, individual CNTs obtained by removal of the template behaved as resistors at 300 K. The CNT/Nb oxide/Nb junction is thought to be responsible for the Schottky behavior. This structure can be a useful cornerstone in the fabrication of nanotransistors operating at room temperature.</P> <B>Graphic Abstract</B> <P>Vertically aligned carbon-nanotube (CNT) arrays were fabricated in thin-film anodic aluminum oxide (AAO) templates on silicon wafers utilizing a niobium (Nb) thin film as the source electrode (see the SEM image and the schematic). The CNT arrays synthesized at 700 °C and above showed Schottky behavior even at room temperature (see the graph). Such structures may be a useful route to the fabrication of nanotransistors operating at room temperature. <img src='wiley_img/16136810-2005-1-5-SMLL200400114-content.gif' alt='wiley_img/16136810-2005-1-5-SMLL200400114-content'> </P>