Ihm K.,Pohang Accelerator Laboratory |
Lim J.T.,Sungkyunkwan University |
Lee K.-J.,Pohang University of Science and Technology |
Kwon J.W.,Sungkyunkwan University |
And 6 more authors.
Applied Physics Letters | Year: 2010
Impressive optical properties of graphene have been attracting the interest of researchers, and, recently, the photovoltaic effects of a heterojunction structure embedded with few layer graphene (FLG) have been demonstrated. Here, we show the direct dependence of open-circuit voltage (Voc) on numbers of graphene layers. After unavoidably adsorbed contaminants were removed from the FLGs, by means of in situ annealing, prepared by layer-by-layer transfer of the chemically grown graphene layer, the work functions of FLGs showed a sequential increase as the graphene layers increase, despite of random interlayer-stacking, resulting in the modulation of photovoltaic behaviors of FLGs/Si interfaces. © 2010 American Institute of Physics.
Kim S.-H.,Sungkyunkwan University |
Kim S.-H.,Korea Institute of Nuclear Safety |
Huh N.-S.,Seoul National University of Science and Technology |
Kim M.-K.,SKKU Advanced Institute of Nanotechnology |
And 5 more authors.
Journal of Mechanical Science and Technology | Year: 2013
Turbulent mixing in a T-junction causes thermal striping which is irregular and frequent fluctuation of thermal layer. Thermal striping is a significant thermal problem because it causes unpredicted high cycle thermal fatigue and fatigue cracking in piping systems. Since this phenomenon is hardly detected by common plant instruments due to high frequency and complex mechanism, numerical approaches are indispensable for a precise evaluation. This research was carried out to define a suitable and effective numerical method for evaluating thermal stress and fatigue induced by thermal striping. A three-dimensional hydro-thermo-mechanical analysis was performed based on one-way separate analysis method to find out the characteristics of stress components and its results were compared to the results of a one-dimensional simplified analysis. It was found that the detailed three-dimensional analysis is indispensable because one-dimensional simplified analysis can overestimate or underestimate according to the assumed heat transfer coefficient and cannot estimate the considerable mean stress effects. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
Kim Y.-H.,ChangSung Co. |
Kim Y.-H.,SKKU Advanced Institute of Nanotechnology |
Lee J.-E.,ChangSung Co. |
Cho S.-K.,ChangSung Co. |
And 6 more authors.
Colloid and Polymer Science | Year: 2012
An ultrathin polydimethylsiloxane (PDMS) layer with a mean thickness of 1 nm was coated on soft magnetic carbonyl iron (CI) particles by using a simple thermal evaporation process, and then their physical characteristics were examined using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetry analysis (TGA), and vibrating sample magnetometry (VSM). Magnetorheological (MR) fluid was prepared by using PDMS-coated CI powder, and its rheological behavior was investigated under different external magnetic field strengths using a rotational rheometer. The CI particles coated by a thin PDMS layer showed higher oxidation temperature than pristine CI particles and MR fluid consisting of PDMS-coated CI particles demonstrated better dispersion stability in a nonmagnetic carrier fluid. © Springer-Verlag 2012.
Jeon J.,Sungkyunkwan University |
Jang S.K.,Sungkyunkwan University |
Jeon S.M.,Sungkyunkwan University |
Yoo G.,Sungkyunkwan University |
And 2 more authors.
IEEE Transactions on Nanotechnology | Year: 2015
We report that control over the grain size and lateral growth of monolayer MoS2 film, yielding a uniform large-area monolayer MoS2 film, can be achieved by submitting the SiO2 surfaces of the substrates to oxygen plasma treatment and modulating substrate temperature in chemical vapor deposition (CVD) process. Scanning electron microscopy and atomic force microscopy images and Raman spectra revealed that the MoS2 lateral growth could be controlled by the surface treatment conditions and process temperatures. Moreover, the obtained monolayer MoS2 films showed excellent scalable uniformity covering a centimeter-scale SiO2/Si substrates, which was confirmed with Raman and photoluminescence mapping studies. Transmission electron microscopy measurements revealed that the MoS2 film of the monolayer was largely single crystalline in nature. Back-gate field effect transistors based on a CVD-grown uniform monolayer MoS2 film showed a good current on/off ratio of ∼106 and a field effect mobility of 7.23 cm2/V·s. Our new approach to growing MoS2 films is anticipated to advance studies of MoS2 or other transition metal dichalcogenide material growth mechanisms and to facilitate the mass production of uniform high-quality MoS2 films for the commercialization of a variety of applications. © 2002-2012 IEEE.
Cho Y.,Sungkyunkwan University |
Choi H.,Samsung |
Kim T.,Sungkyunkwan University |
Kim T.,SKKU Advanced Institute of Nanotechnology
ECS Transactions | Year: 2013
The present semiconductor cleaning technology is based upon chemical cleaning, a high-temperature process that consumes vast amounts of chemicals and ultrapure water. Therefore, this technology gives rise to many environmental issues, and some alternatives are being evaluated. Herein we report, gas cluster cleaning method for cleaning semiconductor devices. Two types of particles such as Ceria (CeO2) and Silica (SiO2) were used to evaluate particle removal efficiency (PRE). It is observed from the field emission scanning electron microscopy (FE-SEM) images that most of particles were removed with PRE more than 90% under various experimental conditions. Further, the pattern damage evaluation is carried out for poly-Si patterns which have width of pattern in the range of 60 to 100 nm. It is observed that there is no pattern damage for various experimental conditions. © The Electrochemical Society.