المؤلفون: Yang, HW Yang, Hyoung Woo, Sohn, JI Sohn, Jung Inn, Yang, JH Yang, Jae Hoon, Jang, JE Jang, Jae Eun, Cha, SN Cha, Seung Nam, Kim, J Kim, Jongmin, Kang, DJ Kang, Dae Joon

المساهمون: 201332005, 110003, Yang, JH Yang, Jae Hoon, Jang, JE Jang, Jae Eun, Yang, HW Yang, Hyoung Woo, Sohn, JI Sohn, Jung Inn, Cha, SN Cha, Seung Nam, Kim, J Kim, Jongmin, Kang, DJ Kang, Dae Joon

الوصف: We report on the epitaxial growth of vanadium dioxide (VO2) thin films on (0001) GaN substrates using a radio frequency magnetron sputtering method and discuss their unusual M2-mediated metal-insulator transition (MIT) properties. We found that large lattice misfits between the VO2 film and the GaN substrate could favor the stabilization of the intermediate insulating M2 phase, which is known to be observed only in either doped or uniaxially strained samples. We demonstrated that the MIT in VO2 films on GaN substrates could be mediated via a monoclinic M2 phase during the transition from a monoclinic M1 to a rutile R phase. This was confirmed by temperature-dependent Raman studies that exhibited both an evident upshift of a high-frequency phonon mode (��V-O) from 618 cm-1 (M1) to 645 cm-1 (M2) and a distinct peak splitting of a low-frequency phonon mode (��V-V) at 221 cm-1 (M2) for increasing temperatures. Moreover, a resistance change of four orders of magnitude was observed for VO2 thin films on GaN substrates, being indicative of the high quality of VO2 thin films. This study may offer great opportunities not only to improve the understanding of M2-mediated MIT behavior in VO2 thin films, but also to realize novel electronic and optoelectronic devices. Copyright �� EPLA, 2015. ; 1

العلاقة: EPL, v.109, no.2; http://hdl.handle.net/20.500.11750/1712Test; 000349555100026; 2-s2.0-84922458217; 1328; 201332005; 110003; 109; EPL

الإتاحة: https://doi.org/20.500.11750/1712Test
https://doi.org/10.1209/0295-5075/109/27004Test
https://hdl.handle.net/20.500.11750/1712Test

المؤلفون: Kim, J Kim, Jongmin, OH, MS OH, Myung Seok, Choi, CH Choi, Chang-Hyung, Kang, SM Kang, Sung-Min, Kwak, MJ Kwak, Moo Jin, You, JB You, Jae Bem, Im, SG Im, Sung Gap, Lee, CS Lee, Chang-Soo

مصطلحات موضوعية: VAN-DER-WAALS, PHOTONIC CRYSTALS, PATCHY PARTICLES, CAPILLARY FORCES, BLOCK-COPOLYMERS, WATER-INTERFACE, NANOPARTICLES, POLYMER, SHAPE, ORGANIZATION

الوصف: The three-dimensional (3D) clustering of Janus cylinders is controlled by simply tuning the cylinder geometry and hydrophobic interactions. Janus cylinders were prepared by combining two approaches: micromolding and initiated chemical vapor deposition (iCVD). Hydrophilic cylinders with a flat-or convex-top curvature were prepared by micromolding based on surface tension-induced flow. The iCVD process then provides a hydrophobic domain through the simple and precise deposition of a polymer film on the top surface, forming monodisperse Janus microcylinders. We use these Janus cylinders as building blocks to form 2D or 3D clusters via hydrophobic interactions in methanol. We investigate how cylinder geometry or degree of hydrophobic interaction affects the resulting cluster geometries. The convex-top Janus cylinders lead to 3D clustering through tip-to-tip interactions, and the flat-top Janus cylinders lead to 2D clustering through face-to-face attraction. The number of Janus cylinders in 3D clusters is tuned by controlling the degree of hydrophobic (or hydrophilic) interaction.

الإتاحة: https://doi.org/10.1039/c5sm00734hTest
http://hdl.handle.net/10203/200073Test

المؤلفون: Yoo, J.J Yoo, Jae Jun, Kim, J Kim, Jongmin, Im, C. Im, Chang-Hwan, Ye, JC Ye, Jong Chul

الإتاحة: https://doi.org/10.1109/ICCAS.2013.6704191Test
http://hdl.handle.net/10203/188001Test

المؤلفون: Park, H Park, Hyunsin, Yun, S Yun, Sungrack, Kim, J Kim, Jongmin, Park, S Park, Sanghyuk, Yoo, CD Yoo, Chang Dong

الإتاحة: http://hdl.handle.net/10203/172531Test

المؤلفون: Kim, S Kim, Sungwoong, Kim, J Kim, Jongmin, Yun, S Yun, Sungrack, Yoo, CD Yoo Chang Dong

الإتاحة: http://hdl.handle.net/10203/169820Test

المؤلفون: Kim, J Kim, Jongmin, Lee, JH Lee, Jae-Hyug, Song, TH Song, Tae-Ho

الوصف: Characteristic properties of phenolic foam as the interstitial material of a vacuum insulation panel are investigated experimentally. For the measurement of effective thermal conductivity, a vacuum guarded hot plate (VGHP) apparatus is used and the conductivity is measured at various vacuum levels. Radiative properties are found using a Fourier transform infrared spectroscopy (FT-IR) device. Solid conductivity is estimated using the porosity of the foam. Effective thermal conductivity at high level of vacuum is measured to be 5 mW/m K which is sum of solid conductivity (2.56 mW/m K) and radiative conductivity (2.44 mW/m K) with 5% of measurement uncertainty. The pore size of the foam is estimated to be 260 mu m using rarefied gas conduction theory. This ensures insulation performance of phenolic foam up to about 10(-3) atm. Other practical characteristics of phenolic foam as the VIP core material are also discussed. ; 기계공학전공

الإتاحة: https://doi.org/10.1016Test/j.ijheatmasstransfer.2012.05.051
http://hdl.handle.net/10203/103332Test