Graphene Research Center

Singapore, Singapore

Graphene Research Center

Singapore, Singapore

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Reddy M.V.,Ionics | Reddy M.V.,Graphene Research Center | Reddy M.V.,National University of Singapore | Prithvi G.,Ionics | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2014

The compounds, CoN, CoO, and Co3O4 were prepared in the form of nano-rod/particles and we investigated the Li-cycling properties, and their use as an anode material. The urea combustion method, nitridation, and carbothermal reduction methods were adopted to prepare Co3O 4, CoN, and CoO, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and the Brunauer-Emmett-Teller (BET) surface and density methods were used to characterise the materials. Cyclic voltammetry (CV) was performed and galvanostatic cycling tests were also conducted up to 60-70 cycles. The observed reversible capacity of all compounds is of the increasing order CoO, Co 3O4, CoN and all compounds showed negligible capacity fading. CoO allows for Li2O and Co metal to form during the discharge cycle, allowing for a high theoretical capacity of 715 mA h g-1. Co3O4 allows for 4 Li2O and 3Co to form, and has a theoretical capacity of 890 mAhg-1. CoN is the best anode material of the three because the nitrogen allows for Li3N and Co to form, resulting in an even higher theoretical capacity of 1100 mAhg-1 due to the Li3N and Co metal formation. Irrespective of morphology the charge profiles of all three compounds showed a major plateaux ∼2.0 V vs. Li and potential values are almost unchanged irrespective of crystal structure. Electrochemical impedance spectroscopy (EIS) was performed to understand variation resistance and capacitance values. © 2013 American Chemical Society.


News Article | December 1, 2016
Site: www.cemag.us

All our smart phones have shiny flat AMOLED displays. Behind each single pixel of these displays hide at least two silicon transistors which were mass-manufactured using laser annealing technologies. While the traditional methods to make them uses temperatures above 1,000 C, the laser technique reaches the same results at low temperatures even on plastic substrates (melting temperature below 300 C). Interestingly, a similar procedure can be used to generate crystals of graphene. Graphene is a strong and thin nano-material made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide. Professor Keon Jae Lee's research group at the Center for Multidimensional Carbon Materials within the Institute for Basic Science (IBS) and Professor Choi Sung-Yool's team at Korea Advanced Institute of Science & Technology (KAIST) discovered graphene synthesis mechanism using laser-induced solid-state phase separation of single-crystal silicon carbide (SiC). This study, available in Nature Communications, clarifies how this laser technology can separate a complex compound (SiC) into its ultrathin elements of carbon and silicon. Although several fundamental studies understood the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time. With high resolution microscope images and molecular dynamic simulations, scientists found that a single-pulse irradiation of xenon chloride excimer laser of 30 nanoseconds melts SiC, leading to the separation of a liquid SiC layer, a disordered carbon layer with graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes the sublimation of the separated silicon, while the disordered carbon layer is transformed into a multilayer graphene. "This research shows that the laser material interaction technology can be a powerful tool for next generation of two dimensional nanomaterials," says Choi, adding, "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future." Keon is affiliated with the School of Materials Science and Engineering, KAIST, and Choi with the School of Electrical Engineering and Graphene Research Center, KAIST.


News Article | December 1, 2016
Site: www.eurekalert.org

All our smart phones have shiny flat AMOLED displays. Behind each single pixel of these displays hide at least two silicon transistors which were mass-manufactured using laser annealing technologies. While the traditional methods to make them uses temperatures above 1,000°C, the laser technique reaches the same results at low temperatures even on plastic substrates (melting temperature below 300°C). Interestingly, a similar procedure can be used to generate crystals of graphene. Graphene is a strong and thin nano-material made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide. Prof. KEON Jae Lee's research group at the Center for Multidimensional Carbon Materials within the Institute for Basic Science (IBS) and Prof. CHOI Sung-Yool's team at KAIST discovered graphene synthesis mechanism using laser-induced solid-state phase separation of single-crystal silicon carbide (SiC). This study, available on Nature Communications, clarifies how this laser technology can separate a complex compound (SiC) into its ultrathin elements of carbon and silicon. Although several fundamental studies understood the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time. With high resolution microscope images and molecular dynamic simulations, scientists found that a single-pulse irradiation of xenon chloride excimer laser of 30 nanoseconds melts SiC, leading to the separation of a liquid SiC layer, a disordered carbon layer with graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes the sublimation of the separated silicon, while the disordered carbon layer is transformed into a multilayer graphene. "This research shows that the laser material interaction technology can be a powerful tool for next generation of two dimensional nanomaterials," said Prof. Keon. Prof. Choi added: "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future." IBS Prof. Keon is affiliated with the School of Materials Science and Engineering, KAIST and Prof. Choi with the School of Electrical Engineering and Graphene Research Center, KAIST.


Smart phones have shiny flat AMOLED displays. Behind each single pixel of these displays hide at least two silicon transistors which were mass-manufactured using laser annealing technologies. While the traditional methods to make them uses temperatures above 1,000 °C, the laser technique reaches the same results at low temperatures even on plastic substrates (melting temperature below 300 °C). Interestingly, a similar procedure can be used to generate crystals of graphene. Graphene is a strong and thin nano-material made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide. Prof. KEON Jae Lee's research group at the Center for Multidimensional Carbon Materials (http://cmcm.ibs.re.kr/html/cmcm_en/) within the Institute for Basic Science (IBS) and Prof. CHOI Sung-Yool's team at KAIST discovered graphene synthesis mechanism using laser-induced solid-state phase separation of single-crystal silicon carbide (SiC). This study, available on Nature Communications, clarifies how this laser technology can separate a complex compound (SiC) into its ultrathin elements of carbon and silicon. Although several fundamental studies understood the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time. With high resolution microscope images and molecular dynamic simulations, scientists found that a single-pulse irradiation of xenon chloride excimer laser of 30 nanoseconds melts SiC, leading to the separation of a liquid SiC layer, a disordered carbon layer with graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes the sublimation of the separated silicon, while the disordered carbon layer is transformed into a multilayer graphene. "This research shows that the laser material interaction technology can be a powerful tool for next generation of two dimensional nanomaterials," said Prof. Keon. Prof. Choi added: "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future." IBS Prof. Keon is affiliated with the School of Materials Science and Engineering, KAIST and Prof. Choi with the School of Electrical Engineering and Graphene Research Center, KAIST. Explore further: New technique integrates graphene, graphene oxide and reduced graphene oxide onto silicon chips at room temperature More information: Insung Choi et al. Laser-induced phase separation of silicon carbide, Nature Communications (2016). DOI: 10.1038/ncomms13562


Woo Y.S.,Graphene Research Center | Seo D.H.,Graphene Research Center | Yeon D.-H.,Material Application Group | Heo J.,Graphene Research Center | And 7 more authors.
Carbon | Year: 2013

We report on the fabrication of completely uniform monolayer graphene on a metal thin film over a 150 mm Si substrate at a low temperature of 600 C by inductively coupled plasma-enhanced chemical vapor deposition (ICPCVD). Through novel use of bimetallic catalyst such as CuNi and AuNi alloys we were able to control catalytic reaction at the metal surface and grow complete monolayer graphene with a Ni content less than 20 at.%. We also found that the 2D/G intensity ratio in the Raman spectra was almost invariant with growth time and the C 1s peak in the XPS spectra was observed only at the metal surface. This implies that monolayer graphene was possibly grown on these Ni-doped copper and gold catalysts by a self-limiting surface reaction under our CVD condition. From DFT calculations, it was shown that the catalytic activity of normally inactive Cu and Au could be enhanced through the addition of Ni atoms at surface sites, providing graphene growth at lower temperatures than pure Cu or Au. The carrier mobility of graphene films grown on these CuNi and AuNi alloy catalyst was measured to be over 9000 cm2 V-1 s-1 at room temperature, which is comparable to that of CVD graphene film grown on Cu foil. Therefore, we suggest an efficient way in growing a complete monolayer graphene on thin films at low temperatures, which could be a key issue in the application of graphene devices. © 2013 Elsevier Ltd. All rights reserved.

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