Korea National NanoFab Center

Daejeon, South Korea

Korea National NanoFab Center

Daejeon, South Korea
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Yu S.,Korea Advanced Institute of Science and Technology | Han H.J.,Korea Advanced Institute of Science and Technology | Kim J.M.,Korea Advanced Institute of Science and Technology | Yim S.,Korea Advanced Institute of Science and Technology | And 8 more authors.
ACS Nano | Year: 2017

With the recent emergence of flexible and wearable optoelectronic devices, the achievement of sufficient bendability and stretchability of transparent and conducting electrodes (TCEs) has become an important requirement. Although metal-mesh-based structures have been investigated for TCEs because of their excellent performances, the fabrication of mesh or grid structures with a submicron line width is still complex due to the requirements of laborious lithography and pattern transfer steps. Here, we introduce an extremely facile fabrication technique for metal patterns embedded in a flexible substrate based on submicron replication and an area-selective delamination (ASD) pattern. The high-yield, area-specific lift-off process is based on the principle of solvent-assisted delamination of deposited metal thin films and a mechanical triggering effect by soft wiping or ultrasonication. Our fabrication process is very simple, convenient, and cost-effective in that it does not require any lithography/etching steps or sophisticated facilities. Moreover, their outstanding optical and electrical properties (e.g., sheet resistances of 0.43 ω sq-1 at 94% transmittance), which are markedly superior to those of other flexible TCEs, are demonstrated. Furthermore, there is no significant change of resistance over 1000 repeated bending cycles, with a bending radius of 5 mm, and immersion in various solvents such as salt water and organic solvents. Finally, we demonstrate high-performance transparent heaters and flexible touch panels fabricated using the nanomesh electrode, confirming the long-range electrical conduction and reliability of the electrode. © 2017 American Chemical Society.

Jeon H.-J.,Korea National Nanofab Center | Jeong H.S.,Korea Institute of Science and Technology
Macromolecular Research | Year: 2016

We describe a highly efficient technique for nanostructuring silicon (Si) wafer surfaces with high-resolution (< 15 nm) and high aspect ratio (20) structures without any deposition processes. Our strategy is based on advanced secondary sputtering lithography (SSL), which combines physical and chemical plasma etching during an ion bombardment process. Compared with general SSL techniques using Ar gas only, the reactive radicals assisted the SSL and promoted the Si etching rate to simultaneously deposit the etched Si materials onto the side surface of a pre-patterned polymer. In addition, various three-dimensional Si nanostructure shapes could be developed simply by controlling the pre-patterned polymer, thereby providing a simple and versatile approach to customizing this technique. © 2016 The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht

Lee J.O.,Korea Advanced Institute of Science and Technology | Song Y.-H.,Korea Advanced Institute of Science and Technology | Kim M.-W.,Korea Advanced Institute of Science and Technology | Kang M.-H.,Korea National NanoFab Center | And 3 more authors.
Nature Nanotechnology | Year: 2013

Nanoelectromechanical (NEM) switches1-6 have received widespread attention as promising candidates in the drive to surmount the physical limitations currently faced by complementary metal oxide semiconductor technology. The NEM switch has demonstrated superior characteristics including quasi-zero leakage behaviour1, excellent density capability 2 and operation in harsh environments3. However, an unacceptably high operating voltage (4-20 V) has posed a major obstacle in the practical use of the NEM switch in low-power integrated circuits. To utilize the NEM switch widely as a core device component in ultralow power applications7-11, the operation voltage needs to be reduced to 1 Vor below. However, sub-1 Vactuation has not yet been demonstrated because of fabrication difficulties and irreversible switching failure caused by surface adhesion. Here, we report the sub-1 V operation of a NEM switch through the introduction of a novel pipe clip device structure and an effective air gap fabrication technique. This achievement is primarily attributed to the incorporation of a 4-nm-thick air gap, which is the smallest reported so far for a NEM switch generated using a 'top-down' approach. Our structure and process can potentially be utilized in various nanogap-related applications, including NEM switch-based ultralow-power integrated circuits, NEM resonators 12,13, nanogap electrodes for scientific research14 and sensors15. © 2013 Macmillan Publishers Limited. All rights reserved.

Yeon J.,Korea Advanced Institute of Science and Technology | Lee Y.J.,LG Innotek | Yoo D.E.,Korea National NanoFab Center | Yoo K.J.,LG Innotek | And 9 more authors.
Nano Letters | Year: 2013

Nanowires are being actively explored as promising nanostructured materials for high performance flexible electronics, biochemical sensors, photonic applications, solar cells, and secondary batteries. In particular, ultralong (centimeter-long) nanowires are highly attractive from the perspective of electronic performance, device throughput (or productivity), and the possibility of novel applications. However, most previous works on ultralong nanowires have issues related to limited length, productivity, difficult alignment, and deploying onto the planar substrate complying with well-matured device fabrication technologies. Here, we demonstrate a highly ordered ultralong (up to 20 cm) nanowire array, with a diameter of 50 nm (aspect ratio of up to 4 000 000:1), in an unprecedented large (8 in.) scale (2 000 000 strands on a wafer). We first devised a perfectly connected ultralong nanograting master template on the whole area of an 8 in. substrate using a top-down approach, with a density equivalent to that achieved with e-beam lithography (100 nm). Using this large-area, ultralong, high-density nanograting template, we developed a fast and effective method for fabricating up to 20 cm long nanowire arrays on a plastic substrate, composed of metal, dielectric, oxide, and ferroelectric materials. As a suggestion of practical application, a prototype of a large-area aluminum wire grid polarizer was demonstrated. © 2013 American Chemical Society.

Sohn K.-J.,Seoul National University | Park J.H.,Korea National NanoFab Center | Lee D.-E.,Seoul National University | Jang H.-I.,Korea National NanoFab Center | Lee W.I.,Seoul National University
Journal of Micromechanics and Microengineering | Year: 2013

Thermal roll-to-roll imprint lithography (R2RIL) is a simple and low-cost process for the mass production of micro/nanopatterns. However, in that it relies on highly viscous thermoplastic resists, it is limited in its ability to imprint precise patterns at a high speed. Moreover, the concentrated imprint force applied in R2RIL can damage the resist material which is structurally vulnerable at high process temperatures. Therefore, it is important to understand the temperature- and time-dependent characteristics of the resist material as well as the imprinting mechanism when using thermal R2RIL. In this work, the effects of the process temperature and rolling speed on thermal R2RIL of polycarbonate (PC) films were investigated to improve the process efficiency. Micro-scale line patterns were successfully transferred onto PC films from nickel (Ni) mold stamps. Consequently, line patterns with widths in the range of 5-80 ̈m were achieved at a traveling speed of 28.6 mm s-1 and process temperature of 150 °C, which is just above the glass transition temperature (Tg). In addition, the patterning performance was investigated for different temperatures, rolling speeds and pattern sizes. The imprinted pattern profiles were measured by an alpha-step surface profiler to investigate the patterning performance. The results show that a much better imprint performance was achieved at 150 °C, compared to the result at temperatures below Tg. The physical mechanisms of thermal R2RIL on a PC film were studied by a finite-element analysis and the patterning process was successfully demonstrated by a visco-plastic deformation model. © 2013 IOP Publishing Ltd.

Park J.H.,Korea National NanoFab Center | Park H.-H.,Yonsei University
Micro and Nano Letters | Year: 2011

Piezoelectric (PZT) (Pb(Zr 0.52Ti 0.48)O 3) thick film-based microtransducers demonstrate excellent piezoelectric performances. PZT thick films on Si-based substrate can be used as piezoelectric actuators and sensors with the introduction of microelectromechanical system technology and the screen printing method. However, the thick films made just by the screen printing method have high porosity compared with bulk product, and the PZT thick films on Si-based substrate have problems regarding degradation of active materials and interface properties owing to inter-diffusion or reaction between Si substrate and PZT materials at high temperature for sintering. Thus, the authors have fabricated screen printed PZT thick films on Si substrate using the screen printing method and sol infiltration for enhancing densification. Ethanol-based photo-cross-linkable sol and conventional diol-based sol were used to compare influence of patterning process. Thick films with relative high densities at low temperature, 800°C and without inter-diffusion and reaction between the layers and thick film were accomplished. Also, it was revealed that the PZT thick film treated by ethanol-based photo-cross-linkable sol showed better electrical properties as well as excellent patternability. © 2011 The Institution of Engineering and Technology.

Cho S.-Y.,Korea Advanced Institute of Science and Technology | Jeon H.-J.,Korea National Nanofab Center | Yoo H.-W.,Agency for Defense Development | Cho K.M.,Korea Advanced Institute of Science and Technology | And 3 more authors.
Nano Letters | Year: 2015

Enhancement of the fluorescence intensity of quantum dot (QD)-polymer nanocomposite arrays is an important issue in QD studies because of the significant reduction of fluorescence signals of such arrays due to nonradiative processes in densely packed polymer chains in solid films. In this study, we enhance the fluorescence intensity of such arrays without significantly reducing their optical transparency. Enhanced fluorescence is achieved by hybridizing ultrathin plasmonic Au nanowalls onto the sidewalls of the arrays via single-step patterning and hybridization. The plasmonic Au nanowall induces metal-enhanced fluorescence, resulting in a maximum 7-fold enhancement of the fluorescence signals. We also prepare QD nanostructures of various shapes and sizes by controlling the dry etching time. In the near future, this facile approach can be used for fluorescence enhancement of colloidal QDs with plasmonic hybrid structures. Such structures can be used as optical substrates for imaging applications and for fabrication of QD-LED devices. © 2015 American Chemical Society.

Park W.I.,Korea Advanced Institute of Science and Technology | Kim K.,Korea Advanced Institute of Science and Technology | Jang H.-I.,Korea National NanoFab Center | Jang H.-I.,University of Seoul | And 5 more authors.
Small | Year: 2012

The synergetic combination of low-temperature thermal assistance with solvent annealing for the self-assembly of block copolymers with a large Flory-Huggins interaction parameter simultaneously achieves sub-10 nm resolution and sub-1 minute annealing time. It is shown that this method is applicable to different geometries of patterns such as nanoscale dots, lines, and holes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PubMed | Agency for Defense Development, Korea National Nanofab Center and Korea Advanced Institute of Science and Technology
Type: Journal Article | Journal: Nano letters | Year: 2016

The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (25) structure (14 nm thickness) composed of ultrasmall grains (5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of 5 nm was fabricated by secondary sputtering via Ar(+) bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (R/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of 5 nm within a highly ordered, tall nanowire array structure.

In this study, hybrid-structured metal mesh (HMM) films as potential flexible transparent electrodes, composed of aligned micro-sized metal fibers integrated into random network of metal nanofibers, were fabricated by the combination of electrospinning and metal deposition. These naturally fiber-bridged HMMs, with a gold layer thickness of 85 nm, exhibited a high transmittance of around 90% and a sheet resistance of approximately 10 sq

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