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Tension assisted metal transfer of graphene for Schottky diodes onto wafer scale substrates
Lee, Jooho,Lee, Su Chan,Kim, Yongsung,Heo, Jinseong,Lee, Kiyoung,Lee, Dongwook,Kim, Jaekwan,Lee, Sunghee,Lee, Chang Seung,Nam, Min Sik,Jun, Seong Chan IOP 2016 Nanotechnology Vol.27 No.7
<P>We developed an effective graphene transfer method for graphene/silicon Schottky diodes on a wafer as large as 6 inches. Graphene grown on a large scale substrate was passivated and sealed with a gold layer, protecting graphene from any possible contaminant and keeping good electrical contact. The Au/graphene was transferred by the tension-assisted transfer process without polymer residues. The gold film itself was used directly as the electrodes of a Schottky diode. We demonstrated wafer-scale integration of graphene/silicon Schottky diode using the proposed transfer process. The transmission electron microscopy analysis and relatively low ideality factor of the diodes indicated fewer defects on the interface than those obtained using the conventional poly(methyl methacrylate)-assisted transfer method. We further demonstrated gas sensors as an application of graphene Schottky diodes.</P>
Comparison of the Gut Microbiotas of Healthy Adult Twins Living in South Korea and the United States
Lee, Sunghee,Sung, Joohon,Lee, JungEun,Ko, GwangPyo American Society for Microbiology 2011 Applied and environmental microbiology Vol.77 No.20
<B>ABSTRACT</B><P>We compared the composition of the fecal microbiotas of Korean and U.S. adult twins. Our data indicated that the gut microbiota shows some signature of biogeography, potentially mediated by differences in diet and/or other environmental factors; however, these regional differences may be masked by other phenotypic variations, such as obesity.</P>
Lee, Young Hoon,Park, Sunghee,Oh, Jihun,Shin, Jong Won,Jung, Jaehoon,Yoo, Seunghyup,Lee, Min Hyung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.28
<P>A synthetic approach to highly efficient thermally activated delayed fluorescence (TADF) is proposed that uses ortho donor (D) acceptor (A) compounds (PXZoB, DPAoB, and CzoB), wherein the acceptor is based on triarylboron and the donor is phenoxazine (PXZ), diphenylamine (DPA), or carbazole (Cz). Combined with the ortho D-A connectivity, the bulky nature of the triarylboron endows the D-A dyads with inherent steric 'locking' for a highly twisteD-Arrangement, leading to a small energy difference between singlet and triplet excited states (Delta E-sT) and thus exhibiting very efficient TADF with microsecond-range lifetimes. In sharp contrast, the Corresponding para D-A derivatives, DPApB and CzpB, only display short-lived, normal fluorescence. Organic light-emitting diodes (OLEDs) incorporating the proposed ortho D-A compounds as emitters display orange, greenish-blue, and pure blue emission and exhibit high external quantum efficiency (eta(EQE)). In particular, the pure blue OLEDs based on the proposed ortho D-A emitters with a carbazole donor (CzoB) show a record-high eta(EQE) of 22.6% with CIE color coordinates of (0.139, 0.150), well illustrating the validity of the proposeD-Approach. Upon optical optimization, the eta(EQE) is further improved to 24.1%.</P>
Lee, Changyeol,Kim, Soonok,Li, Wei,Bang, Sunghee,Lee, Hanna,Lee, Hyun-Jung,Noh, Eun-Young,Park, Jung-Eun,Bang, Woo Young,Shim, Sang Hee Springer Science and Business Media LLC 2017 Journal of antibiotics Vol.70 No.6
<P>Endophytes, important plant-associated mycobionts, have attracted a great deal of attention because of their bioactive secondary metabolites. Even though halophytes have been reported to overcome salt stress via associations with their endophytes, few studies have investigated the metabolites produced by the endophytes from halophytes. In this study, a dark septate endophytic fungal strain (JS0464), identified as Gaeumannomyces sp. by ITS sequencing, was isolated from the rhizome of a halophyte, Phragmites communis, in Suncheon bay, South Korea. This strain was cultured on a large scale and extracted with ethyl acetate. Chemical investigations of extracts of JS0464 led to the isolation of two glycosylated dialkylresorcinol derivatives (1-2), an anthraquinone derivative (3) and eight known compounds (4-11), which were identified by spectroscopic analyses incorporating one-dimensional/2D NMR and MS. Nine compounds showed significant nitric oxide reduction activity in lipopolysaccharide-stimulated microglia BV-2 cells, seven of which did not impair cell viability. The results suggest that endophytes from the halophytes could be potential resources for bioactive natural products.</P>
Adaptive Rate Control Scheme for Streaming-based Content Sharing Service
( Sunghee Lee ),( Kwangsue Chung ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.4
This paper presents an adaptive rate control scheme for streaming-based content sharing service. This scheme delivers multimedia contents from a user device to another device or seamlessly redirects streaming service across heterogeneous user devices. In the proposed scheme, a streaming server adjusts video quality level according to the network and client status. Our scheme is different from other rate control schemes, because the video quality at the server is decided not only based on the available bandwidth, but also based on the device characteristics and bandwidth requirement at the access network. We also propose a bandwidth estimation method to achieve more equitable bandwidth allocations among streaming flows competing for the same narrow link with different Round Trip Times (RTTs). Through the simulation, we prove that our scheme improves the network stability and the quality of streaming service by appropriately adjusting the quality of the video stream. The simulation results also demonstrate the ability of the proposed scheme in ensuring RTT-fairness while remaining throughput efficient.
Technology Spillover Effect from Early Supplier Involvement Strategy in New Product Development
Sunghee Lee,Booyun Cho 한국인터넷전자상거래학회 2015 인터넷전자상거래연구 Vol.15 No.2
In the era of time-base competition, firms try to introduce new products faster by reducing time of developing a new product. To do so, early supplier involvement has been considered in R&D(Research & Development) stage with supplier development and tight relationship control. Few existing studies considered two-sided effects(i.e, cost reductions from ESI(Early Supplier Involvement) and additional control costs). Moreover, accumulated knowledge from NPD(New Product Development) would contribute to improve the efficiency of production stage(i.e., Technology Spillover Effect). In this study, we try to build in-house and outsourcing R&D models to identify the impacts of overall cost factors. We classify the functions of a product into base and assisting functions, assuming that the only assisting ones can be outsourced with ESI situations. With the comparison between in-house and outsourced R&D decision, we hope the managers of buying firms could find optimal decisions. Implications are discussed along with the results.
Crack-Release Transfer Method of Wafer-Scale Grown Graphene Onto Large-Area Substrates
Lee, Jooho,Kim, Yongsung,Shin, Hyeon-Jin,Lee, ChangSeung,Lee, Dongwook,Lee, Sunghee,Moon, Chang-Yul,Lee, Su Chan,Kim, Sun Jun,Ji, Jae Hoon,Yoon, Hyong Seo,Jun, Seong Chan American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.15
<P>We developed a crack-release graphene transfer technique for opening up possibilities for the fabrication of graphene-based devices. Graphene film grown on metal catalysts/SiO<SUB>2</SUB>/Si wafer should be scathelessly peeled for sequent transferring to a target substrate. However, when the graphene is grown on the metal catalyst on a silicon substrate, there is a large tensile stress resulting from the difference of the coefficient of thermal expansion in the catalyst and silicon. The conventional methods of detaching graphene from metal catalysts were found to induce considerable mechanical damage on graphene films during separation processes including metal wet etching. Here we report a new technique wherein bubbles generated by electrolysis reaction separate thin metal catalysts from the SiO<SUB>2</SUB>/Si wafer. The dry attachment of graphene to the target wafer was processed utilizing a wafer to wafer bonding technique in a vacuum. We measured the microscopic image, Raman spectra, and electrical properties of the transferred graphene. The optical and electrical properties of the graphene transferred by the bubbles/dry method are better than those of the graphene obtained by mechanical/wet transfer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-15/am502565z/production/images/medium/am-2014-02565z_0005.gif'></P>
A MULTIPATH CONGESTION CONTROL SCHEME FOR HIGH-QUALITY MULTIMEDIA STREAMING
( Sunghee Lee ),( Kwangsue Chung ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1
As network adaptive streaming technology becomes increasingly common, transport protocol also becomes important in guaranteeing the quality of multimedia streaming. At the same time, because of the appearance of high-quality video such as Ultra High Definition (UHD), preventing buffering as well as preserving high quality while deploying a streaming service becomes important. The Internet Engineering Task Force recently published Multipath TCP (MPTCP). MPTCP improves the maximum transmission rate by simultaneously transmitting data over different paths with multiple TCP subflows. However, MPTCP cannot preserve high quality, because the MPTCP subflows slowly increase the transmission rate, and upon detecting a packet loss, drastically halve the transmission rate. In this paper, we propose a new multipath congestion control scheme for high-quality multimedia streaming. The proposed scheme preserves high quality of video by adaptively adjusting the increasing parameter of subflows according to the network status. The proposed scheme also increases network efficiency by providing load balancing and stability, and by supporting fairness with single-flow congestion control schemes.
Sunghee Lee,Ahram Cho,Ohsoo Na,Seongmin Sohn 한국인터넷전자상거래학회 2015 인터넷전자상거래연구 Vol.15 No.5
When a manufacturer’s profit level depends on a supplier’s selling price, the supplier has two options according to whether it seeks the public purpose or private profit. The lava water industrialization support center under Jeju Technopark plays a supplying role for the lava water to the nearby companies. This paper analytically shows that the strategically different approaches by the supplier influences the manufacturer’s production pattern. Furthermore, we provide the basis for understanding the public supplier’s non-public action.