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GROWTH OF HIGH QUALITY ZINC OXIDE NANOWIRES BY SIMPLE OXIDATION OF ZINC POWDER IN AIR
TAE-WOONG KOO,DONGMOK WHANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2008 NANO Vol.3 No.6
Single-crystal ZnO nanowires are synthesized by direct oxidation of zinc particles in air at a temperature much lower than the melting temperature of zinc solids. This simple and low-cost technique produces dense and high-quality ZnO nanowires. SEM and TEM studies revealed that as-grown ZnO nanowires have a uniform diameter and defect-free single-crystal structure. The growth direction of ZnO nanowires is the a axis, which is different from the common growth direction of one-dimensional ZnO structure. Room temperature PL spectra of ZnO nanowires grown with different oxygen pressures indicated that the quality of ZnO nanowires grown in air is much better than that of wires grown at reduced oxygen pressure. The excellent property of ZnO nanowires grown in air was confirmed by electrical transport measurements of individual ZnO nanowire field effect transistors.
Template-Assisted CVD Growth of Silicon Nanowires on a Gram Scale
Sun-Hwak Woo,Dongmok Whang 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
Silicon nanowires (SiNWs) oer an ideal basis to study the eects of quantum connement and its possible applications due to its predominant role in semiconductor technology. The fabrication of the SiNWs has been extensively studied, but mass production of single-crystal SiNWs is still both challeging and nessasary. We report chemical vapor deposition (CVD) growth of silicon nanowires on a gram scale by using the two-dimensional (2D) hexagonal mesoporous solid SBA-15 as a template. This new method for growing SiNWs maximizes the number of catalytic metal nanoparticles by using a 3D silica host, whose surface area is much greater than that of the conventional 2D substrate, which results in the mass production of single-crystal SiNWs. Silicon nanowires (SiNWs) oer an ideal basis to study the eects of quantum connement and its possible applications due to its predominant role in semiconductor technology. The fabrication of the SiNWs has been extensively studied, but mass production of single-crystal SiNWs is still both challeging and nessasary. We report chemical vapor deposition (CVD) growth of silicon nanowires on a gram scale by using the two-dimensional (2D) hexagonal mesoporous solid SBA-15 as a template. This new method for growing SiNWs maximizes the number of catalytic metal nanoparticles by using a 3D silica host, whose surface area is much greater than that of the conventional 2D substrate, which results in the mass production of single-crystal SiNWs.
Deoxyribonucleic Acid Sensitive Graphene Field-Effect Transistors
HWANG, Jongseung,KIM, Heetae,LEE, Jaehyun,WHANG, Dongmok,HWANG, Sungwoo The Institute of Electronics, Information and Comm 2011 IEICE transactions on electronics Vol. No.
<P>We have investigated the effect of deoxyribonucleic acid (DNA) adsorption on a graphene field-effect-transistor (FET) device. We have used graphene which is grown on a Ni substrate by chemical vapour deposition. The Raman spectra of our graphene indicate its high quality, and also show that it consists of only a few layers. The current-voltage characteristics of our bare graphene strip FET show a hole conduction behavior, and the gate sensitivity of 0.0034µA/V, which is reasonable with the size of the strip (5×10µm<SUP>2</SUP>). After the adsorption of 30 base pairs single-stranded poly (dT) DNA molecules, the conductance and gate operation of the graphene FET exhibit almost 11% and 18% decrease from those of the bare graphene FET device. The observed change may suggest a large sensitivity for a small enough (nm size) graphene strip with larger semiconducting property.</P>
Huynh Van, Ngoc,Lee, Jae-Hyun,Whang, Dongmok,Kang, Dae Joon The Royal Society of Chemistry 2015 Nanoscale Vol.7 No.27
<▼1><▼1><P>Nanowire-based ferroelectric-complementary metal–oxide–semiconductor (NW FeCMOS) nonvolatile memory devices were successfully fabricated by utilizing single n- and p-type Si nanowire ferroelectric-gate field effect transistors (NW FeFETs) as individual memory cells.</P></▼1><▼2><P>Nanowire-based ferroelectric-complementary metal–oxide–semiconductor (NW FeCMOS) nonvolatile memory devices were successfully fabricated by utilizing single n- and p-type Si nanowire ferroelectric-gate field effect transistors (NW FeFETs) as individual memory cells. In addition to having the advantages of single channel n- and p-type Si NW FeFET memory, Si NW FeCMOS memory devices exhibit a direct readout voltage and ultralow power consumption. The reading state power consumption of this device is less than 0.1 pW, which is more than 10<SUP>5</SUP> times lower than the ON-state power consumption of single-channel ferroelectric memory. This result implies that Si NW FeCMOS memory devices are well suited for use in non-volatile memory chips in modern portable electronic devices, especially where low power consumption is critical for energy conservation and long-term use.</P></▼2></▼1>
Van, Ngoc Huynh,Lee, Jae-Hyun,Whang, Dongmok,Kang, Dae Joon Springer Berlin Heidelberg 2015 Nano-micro letters Vol.7 No.1
<P>A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). We overcame the interfacial layer problem by incorporating P(VDF-TrFE) as a ferroelectric gate using a low-temperature fabrication process. Our memory devices exhibited excellent memory characteristics with a low programming voltage of ±5 V, a large modulation in channel conductance between ON and OFF states exceeding 10<SUP>5</SUP>, a long retention time greater than 3 × 10<SUP>4</SUP> s, and a high endurance of over 10<SUP>5</SUP> programming cycles while maintaining an <I>I</I><SUB>ON</SUB>/<I>I</I><SUB>OFF</SUB> ratio higher than 10<SUP>2</SUP>.</P>
Photosensitive Graphene P-N Junction Transistors and Ternary Inverters
Kim, Jun Beom,Li, Jinshu,Choi, Yongsuk,Whang, Dongmok,Hwang, Euyheon,Cho, Jeong Ho American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.15
<P>We investigate the electric transport in a graphene-organic dye hybrid and the formation of p-n junctions. In the conventional approach, graphene p-n junctions are produced by using multiple electrostatic gates or local chemical doping, which produce different types of carriers in graphene. Instead of using multiple gates or typical chemical doping, a different approach to fabricate p-n junctions is proposed. The approach is based on optical gating of photosensitive dye molecules; this method can produce a well-defined sharp junction. The potential difference in the proposed p-n junction can be controlled by varying the optical power of incident light. A theoretical calculation based on the effective medium theory is performed to thoroughly explain the experimental data. The characteristic transport behavior of the photosensitive graphene p-n junction opens new possibilities for graphene-based devices, and we use the results to fabricate ternary inverters. Our strategy of building a simple hybrid p-n junction can further offer many opportunities in the near future of tuning it for other optoelectronic functionalities.</P> [FIG OMISSION]</BR>