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Single Crystalline Graphene-based Transparent Electrode with Extremely High Folding Resistance
노지수,박호범 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Graphene is a promising substitute of current transparent conducting materials due to its outstanding physical properties. However, polycrystalline polycrystalline graphene (PCG) with numerical structural defects is generally used for the transparent electrode studies. Single crystalline graphene (SCG) has never been used as transparent electrode because it has been a great challenge to synthesize it with large size and some simulation studies show that electrical and mechanical properties would be the same with PCG with large grain size. Here we demonstrate transparent flexible electrode using SCG and compared its properties with PCG. We have confirmed SCG has much improved mechanical and barrier properties and especially the sheet resistance of SCG-based electrode maintained during 10000 times of folding test with 0.5 mm of folding radius. This result shows better macroscopic properties of SCG and its advantages for applying electronic devices.
노지수,이현희,박호범 한국막학회 2016 한국막학회 총회 및 학술발표회 Vol.2016 No.11
Graphene is well-known as a perfect barrier because of its dense and delocalized cloud consisting of p-orbitals. However, graphene membrane synthesized by chemical vapor deposition (CVD) intrinsically contains structural defects (e.q., grain boundaries and point defects), which allow any small molecules to penetrate through the defective graphene membrane. Here we prepared polycrystalline graphene membranes including such defects, and investigated the gas transport behavior through the graphene membrane. Also, we compared the gas permeation behavior (or barrier properties) of large-area, single crystalline graphene membrane without any structural defects.
Synthesis and characterization of grain boundaries-free CVD graphene
노지수,박호범,이민용,유명진,윤희욱 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Large-area monolayer graphene can be synthesized by chemical vapor deposition (CVD) on catalytic copper metal surface. However, the graphene from CVD method usually shows inferior properties as compared to theoretical value of perfect graphene without any structural defects including point defects and grain boundaries. It is widely accepted that the presence of grain boundaries in graphene can lower its outstanding physical properties. In this regard, the synthesis of high-quality graphene (close to single crystal graphene monolayer) has been extensively studied. Likewise, we have prepared a high-quality, large-area graphene with a high carrier mobility of ~12,000 cm2/Vs by using well-oriented copper foil and improved CVD method. Such graphene has still lots of point defects, but no grain boundaries which help improve the quality CVD graphene.
Adhesion between Graphene and Various Polymer Substrates
노지수,이현희,박호범 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
The adhesion between graphene and polymer is important to prepare graphene-containing products such as composites, barriers and electronic devices. Poor adhesion leads to long term stability degradation of graphene based product, because water or other molecules exiting in air are easily adsorbed between the graphene surface and polymer. However, understanding the adhesion of graphene to other material is not simple due to the various influencing factors such as surface roughness, surface energy, graphene thickness and wettability. Here, we studied the relationship between surface free energy and adhesion force of graphene to common polymers. The surface free energy was calculated by contact angle measurement and relative adhesion force was inferenced by delaminating graphene sheets from Cu foil. This results can provide a clue for designing polymer materials with desired adhesion force to graphene surface.
Growth of high-quality graphene monolayer by chemical vapor deposition
노지수,박호범,이민용,윤희욱,유명진 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Chemical vapor deposition (CVD) using Cu catalyst is the most possible way for producing large-size graphene monolayer. It has been a great challenge to prepare high quality graphene to improve graphene properties since graphene from CVD method usually has grain boundaries which degrade its electrical properties. Recently, centimeter-size single crystal graphene has been synthesized by reducing nucleation density of graphene. However, more practical synthesis of single crystal graphene is still desirable for large area application. Here we demonstrate large-area, single crystal graphene sheet with a high carrier mobility of ~12,000 ㎠/Vs, using thermal CVD method. We found the structure defects of graphene arestrongly dependent on the catalytic Cu substrate such as grain size, crystal structure and surface condition.