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Double-layer CVD graphene as stretchable transparent electrodes
Won, Sejeong,Hwangbo, Yun,Lee, Seoung-Ki,Kim, Kyung-Shik,Kim, Kwang-Seop,Lee, Seung-Mo,Lee, Hak-Joo,Ahn, Jong-Hyun,Kim, Jae-Hyun,Lee, Soon-Bok The Royal Society of Chemistry 2014 Nanoscale Vol.6 No.11
<P>The stretchability of CVD graphene with a large area is much lower than that of mechanically exfoliated pristine graphene owing to the intrinsic and extrinsic defects induced during its synthesis, etch-out of the catalytic metal, and the transfer processes. This low stretchability is the main obstacle for commercial application of CVD graphene in the field of flexible and stretchable electronics. In this study, artificially layered CVD graphene is suggested as a promising candidate for a stretchable transparent electrode. In contrast to single-layer graphene (SLG), multi-layer graphene has excellent electromechanical stretchability owing to the strain relaxation facilitated by sliding among the graphene layers. Macroscopic and microscopic electromechanical tensile tests were performed to understand the key mechanism for the improved stretchability, and crack generation and evolution were systematically investigated for their dependence on the number of CVD graphene layers during tensile deformation using lateral force microscopy. The stretchability of double-layer graphene (DLG) is much larger than that of SLG and is similar to that of triple-layer graphene (TLG). Considering the transmittance and the cost of transfer, DLG can be regarded as a suitable candidate for stretchable transparent electrodes.</P>
Graphene-based crack lithography for high-throughput fabrication of terahertz metamaterials
Won, Sejeong,Jung, Hyun-June,Kim, Dasom,Lee, Sang-Hun,Van Lam, Do,Kim, Hyeon-Don,Kim, Kwang-Seop,Lee, Seung-Mo,Seo, Minah,Kim, Dai-Sik,Lee, Hak-Joo,Kim, Jae-Hyun Elsevier 2020 Carbon Vol.158 No.-
<P><B>Abstract</B></P> <P>Terahertz (THz) nanoantennas have significant potential for versatile applications in THz spectroscopy because of their capability for strong electromagnetic field localization. Electron-beam lithography or focused ion beam machining is typically employed to fabricate nanoantenna structures. These nanolithography methods present limitations in the widespread utilization of THz nanoantennas because of their high cost and low productivity. In this work, we proposed graphene-based crack lithography as a high throughput fabrication method for nanoantenna structures. A double-layer graphene interface was introduced to enable independent control of the nanoantenna dimensions and provide graphene-based nanoantenna structures. We analyzed the underlying mechanism of graphene-based cracking and developed an analytical model governing the geometric parameters of the fabricated nanostructures. As a vital application of the fabricated nanoantenna structures, we demonstrated the highly sensitive detection of <SMALL>D</SMALL>-Glucose molecules. Graphene-based crack lithography can provide a cost-effective method for generating nanoantenna structures with the desired characteristics and can accelerate the development of practical applications of electromagnetic metamaterials.</P> <P><B>Graphical abstract</B></P> <P>Nanoantennas of various materials with desired terahertz resonance characteristics can be readily manufactured on a large scale using the graphene-based crack lithography.</P> <P>[DISPLAY OMISSION]</P>
Graphene-based stretchable and transparent moisture barrier
Won, Sejeong,Van Lam, Do,Lee, Jin Young,Jung, Hyun-June,Hur, Min,Kim, Kwang-Seop,Lee, Hak-Joo,Kim, Jae-Hyun IOP 2018 Nanotechnology Vol.29 No.12
<P>We propose an alumina-deposited double-layer graphene (2LG) as a transparent, scalable, and stretchable barrier against moisture; this barrier is indispensable for foldable or stretchable organic displays and electronics. Both the barrier property and stretchability were significantly enhanced through the introduction of 2LG between alumina and a polymeric substrate. 2LG with negligible polymeric residues was coated on the polymeric substrate via a scalable dry transfer method in a roll-to-roll manner; an alumina layer was deposited on the graphene via atomic layer deposition. The effect of the graphene layer on crack generation in the alumina layer was systematically studied under external strain using an <I>in situ</I> micro-tensile tester, and correlations between the deformation-induced defects and water vapor transmission rate were quantitatively analyzed. The enhanced stretchability of alumina-deposited 2LG originated from the interlayer sliding between the graphene layers, which resulted in the crack density of the alumina layer being reduced under external strain.</P>
Lee, Won Seok,Won, Sejeong,Park, Jeunghee,Lee, Jihye,Park, Inkyu RSC Pub 2012 Nanoscale Vol.4 No.11
<P>Controlled alignment and mechanically robust bonding between nanowires (NWs) and electrodes are essential requirements for reliable operation of functional NW-based electronic devices. In this work, we developed a novel process for the alignment and bonding between NWs and metal electrodes by using thermo-compressive transfer printing. In this process, bottom-up synthesized NWs were aligned in parallel by shear loading onto the intermediate substrate and then finally transferred onto the target substrate with low melting temperature metal electrodes. In particular, multi-layer (e.g. Cr/Au/In/Au and Cr/Cu/In/Au) metal electrodes are softened at low temperatures (below 100 °C) and facilitate submergence of aligned NWs into the surface of electrodes at a moderate pressure (???5 bar). By using this thermo-compressive transfer printing process, robust electrical and mechanical contact between NWs and metal electrodes can be realized. This method is believed to be very useful for the large-area fabrication of NW-based electrical devices with improved mechanical robustness, electrical contact resistance, and reliability.</P>
Park, Daehoon,Won, Sejeong,Kim, Kwang-Seop,Jung, Joo-Yun,Choi, Jang-Young,Nah, Junghyo Elsevier 2018 Nano energy Vol.54 No.-
<P><B>Abstract</B></P> <P>Generation of electric potential by the flow of an electrolyte droplet on a graphene surface is investigated to develop a liquid motion energy harvester. Most of the research efforts to date have been focused on unveiling the interaction between graphene and an electrolyte droplet. However, other factors that significantly affect the output potential have not been paid much attention. Here, we report the electrostatic charging of graphene during a layer-transfer process and its influence on the enhancement of the performance of graphene-based liquid motion energy harvesting devices. In particular, we investigated the dependence of the output voltage on the triboelectric properties of the substrate. Our finding indicates that the triboelectric surface charging of graphene is significantly influenced by physisorption between graphene and the underlying substrate. Therefore, it directly affects the output power generation and the concentration of electrolyte solution at which the maximum power generation can be achieved. The method presented here is a simple route to further improve the output performance of graphene-based liquid motion energy harvesting devices and this study extends the physical understanding of charge interaction between graphene and an electrolyte solution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Triboelectrification of the graphene during the transfer process affects the performance of TENG. </LI> <LI> Interaction between the graphene and the substrate determines surface charging of the graphene. </LI> <LI> The origin of the output enhancement mechanism was experimentally investigated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>