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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.
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.
Photogating in the Graphene-Dye-Graphene Sandwich Heterostructure
Lee, Youngbin,Kim, Hyunmin,Kim, Soo,Whang, Dongmok,Cho, Jeong Ho American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.26
<P>In this work, we developed an atomically thin (∼2.5 nm) heterostructure consisting of a monolayer rhodamine 6G (R6G) film as a photoactive layer that was sandwiched between graphene films functioning as channels (graphene-R6G-graphene, G-R-G). Through a comparison of results of both photocurrent measurements and chemically enhanced Raman scattering (CERS) experiments, we found that our G-R-G heterostructure exhibited ∼7 and ∼30 times better performance than R6G-attached single-graphene (R6G-graphene, R-G) and MoS<SUB>2</SUB> devices, respectively; here, the CERS enhancement factor was highly correlated with the relative photoinduced Dirac voltage change. Furthermore, the photocurrent of the G-R-G device was found to be ∼40 times better than that of the R-G photodetector. The top graphene was highly operative in the monolayer, of which the performance is significantly deteriorated by fluorescence and tailored charge transfer efficiency with the increment of R6G film thickness. Overall, the responsivity of the G-R-G photodetector was ∼40 times higher than that of the R-G photodetector because of the more efficient carrier transfer between the organic dye and graphene induced by weaker π-π interactions between the top and bottom graphene channels in the former device. This atomically thin (∼2.5 nm) and highly photosensitive photodetector can be employed for post-Si-photodiode (PD) image sensors, single-photon detection devices, and optical communications.</P> [FIG OMISSION]</BR>
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>
Direct growth of graphene on rigid and flexible substrates: progress, applications, and challenges
Pham, Viet Phuong,Jang, Hyeon-Sik,Whang, Dongmok,Choi, Jae-Young The Royal Society of Chemistry 2017 Chemical Society reviews Vol.46 No.20
<P>Graphene has recently been attracting considerable interest because of its exceptional conductivity, mechanical strength, thermal stability,<I>etc.</I>Graphene-based devices exhibit high potential for applications in electronics, optoelectronics, and energy harvesting. In this paper, we review various growth strategies including metal-catalyzed transfer-free growth and direct-growth of graphene on flexible and rigid insulating substrates which are “major issues” for avoiding the complicated transfer processes that cause graphene defects, residues, tears and performance degradation in graphene-based functional devices. Recent advances in practical applications based on “direct-grown graphene” are discussed. Finally, several important directions, challenges and perspectives in the commercialization of ‘direct growth of graphene’ are also discussed and addressed.</P>