• Carbon letters
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• v.9 no.2
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• pp.131-136
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• 2008

In order to investigate the effect of doping C, N, B and F elements on $TiO_2$ for reducing the band gap, the heat treatment of $TiO_2$ was carried out with tetraethylammonium tetrafluoroborate. Through XRD and XPS analysis, the C, N, B and F doped anatase $TiO_2$ was confirmed. According to the increase of temperature during treatment, the particle size was increased due to aggregation of $TiO_2$ with elements (B, C, N and F). To investigate the capacity of photocatalyst for degradation of dye under solar light, the degradation of acridine orange and methylene blue was conducted. The degradation of dyes was carried out successfully under solar light indicating the effect of doping elements (B, C, N and F) on $TiO_2$ for reducing the band gap effectively.

• Progress in Superconductivity
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• v.14 no.1
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• pp.34-38
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• 2012

The effect of graphene inclusion in the ex-situ $MgB_2$ was analyzed with the help of resistivity behavior and critical current density studies. Amount of graphene was systematically varied from 0% for pristine sample to 3% by the weight of $MgB_2$. Graphene that is considered as a good source of carbon was found to be intact without any significant carbon doping in $MgB_2$ structure as reveled by XRD measurements. There was no signature of graphene inclusion as far as the superconducting transition is concerned which remained same at 39 K for all the samples. The transition width being sensitive to defect doping remained more or less about 2 K for all the samples showing no variation due to doping. Although there was no change in the superconducting transition or transition width, the graphene doped sample showed noticeable decrease in the overall resistivity behavior with respect to decrease in temperature. The graphene inclusion acted as effective pinning centers which have enhanced the upper critical field of these samples.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.246-249
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• 2013

Graphene was obtained on Cu foil by thermal decomposition method. A gas mixture of $H_2$ and $CH_4$ and an ambient annealing temperature of $1,000^{\circ}C$ were used during the deposition for 30 Min., and for the transfer onto $SiO_2/Si$ and Si substrates. The physical properties of graphene were investigated with regard to the effect ofnitrogen atom doping and the various substrates used. The G/2D ratio decreased when the graphene became monolayer graphene. The graphene grown on $SiO_2/Si$ substrate showed a low intensity of the G/2D ratio, because the polarity of the $SiO_2$ layer improved the quality of graphene. The intensity of the G/2D ratio of graphene doped with nitrogen atoms increased with the doping time. The quality of graphene depended on the concentration of the nitrogen doping and chemical properties of substrates. High-quality monolayer graphene was obtained with a low G/2D ratio. The increase in the intensity of the G/2D ratios corresponded to a blue shift in the 2D peaks.

• Carbon letters
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• v.10 no.2
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• pp.123-130
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• 2009

Multi-elements doped $TiO_2$ was prepared as a new photocatalyst in order to decrease the band gap of $TiO_2$ by sol-gel process which can provide the large active sites of $TiO_2$. Multi-elements were doped by using a single precursor, tetraethylammonium tetrafluoroborate (TEATFB). By the benefit of large specific surface area of $TiO_2$ prepared by sol-gel process, catalysts showed initial fast removal of dye. The photoactivity showed that the doped catalysts significantly promote the light reactivity than undoped $TiO_2$. The commendable photoactivity of prepared catalysts is predominantly attributable to the doping of anions which may reduce the band gap.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.133-134
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• 2000

Effect of nitrogen doping on field emission characteristics of patterned Diamond-like Carbon (DLC) films was studied. The patterned DLC films were fabricated by the method reported previously[1]. Nitrogen doping in DLC film was carried out by introducing $N_2$ gas into the vacuum chamber during deposition. Higher emission current density of $0.3{\sim}0.4$ $mA/cm^2$ was observed for the films with 6 at % N than the undoped films but the emission current density decreased with further increase of N contents. Some changes in CN bonding characteristics with increasing N contents were observed. The CN bonding characteristics which seem to affect the electron emission properties of these films were studied by Raman spectroscopy, x-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The electrical resistivity and the optical band gap measurements showed consistence with the above analyses.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.201-201
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• 2009

• Korean Journal of Materials Research
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• v.33 no.4
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• pp.124-129
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• 2023

This study assessed the influences of fluorine introduced into DLC films on the structural and mechanical properties of the sample. In addition, the effects of the fluorine incorporation on the compressive stress in DLC films were investigated. For this purpose, fluorinated diamond-like carbon (F-DLC) films were deposited on cobalt-chromium-molybdenum substrates using radio-frequency plasma-enhanced chemical vapor. The coatings were examined by Raman scattering (RS), Attenuated total reflectance Fourier transform infrared spectroscopic analysis (ATR-FTIR), and a combination of elastic recoil detection analysis and Rutherford backscattering (ERDA-RBS). Nano-indentation tests were performed to measure hardness. Also, the residual stress of the films was calculated by the Stony equation. The ATR-FTIR analysis revealed that F was present in the amorphous matrix mainly as C-F and C-F₂ groups. Based on Raman spectroscopy results, it was determined that F made the DLC films more graphitic. Additionally, it was shown that adding F into the DLC coating resulted in weaker mechanical properties and the F-DLC coating exhibited lower stress than DLC films. These effects were attributed to the replacement of strong C = C by feebler C-F bonds in the F-DLC films. F-doping decreased the hardness of the DLC from 11.5 to 8.8 GPa. In addition, with F addition, the compressive stress of the DLC sample decreased from 1 to 0.7 GPa.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.118.2-118.2
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• 2016

3D NAND 제조에 있어 high-aspect-ratio etch 공정을 견뎌낼 수 있는 hardmask 소재로서 amorphous carbon layer (ACL) 가 각광받고 있으며 hardmask로서의 특성을 향상시키기 위해 다양한 연구가 진행중에 있다 [1]. 본 연구팀의 기존 연구에서 질소 및 붕소 doping 된 ACL 박막의 etch rate 및 Raman 분석을 통해 박막 특성을 확인한 바 있었으나, 공정 중 arcing이 일어나는 등 의도치 않은 문제로 인해 공정 최적화에 일부 문제가 존재하였다. 본 연구에서는 plasma enhanced chemical vapor deposition (PECVD) 공정을 통해 C6H12 기체 및 doping을 위한 NH3 와 B2H6 두 기체를 이용하여 특성 개선된 ACL을 증착하는 과정에서 발생하는 arcing 및 증착 특성을 규명하고자 진공 내 입자의 수농도를 실시간 측정할 수 있는 particle beam mass spectrometer(PBMS)를 적용, 특정 공정 사건 진단 및 해당 사건에서 발생하는 입자를 분석, 증착된 박막의 Raman spectroscopy 결과와 비교 분석하였다.

• Analytical Science and Technology
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• v.8 no.4
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• pp.583-590
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• 1995

Pitch-based mesophase carbon fibers prepared at different temperatures were heat-treated at temperatures lower than those of the preparation and the electrochemical Li doping/undoping characteristics were evaluated in relation to the data of IR, mass, etc. Presence of surface hydroxyls were confirmed by FTIR for lower temperature sample which showed poor anode characteristics. Upon oxidative heating, removal of surface hydroxyls took place, resulting in a remarkable improvement of the electrode characteristics. At the same time, surface roughening took place, which was confirmed by SEM and double layer capacity measurements. In situ mass spectra obesrved during the heat-treatments showed gas evolution of $H_2O$, CO, $CO_2$, $C_2H_4$, and/or $H_2$ depending on the conditions. These data together with those of weight loss and conductivity provided us a valuable information in regard to the evaluation of the electrochemical characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.326-331
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• 2000

We have fabricated the field emitter arrays coated with diamond-like carbon (DLC) films that improved the field emission characteristics. The nitrogen doped DLC films are prepared by the filtered cathodic vacuum are (FCVA) tehnique. The activation energy of the nitrogen doped DLC films are derived from electrical conductivity measurements. The silicon field emission arrays (FEAs) were prepared by the VLSI technique. The turn-on field was rapidly decreasing and the emission current was remarkably increasing the DLC-coated FEAs than the non-coated silicon FEAs. In the nitrogen doped FEAs, the turn-on field decreased and the emission current increased with increasing the nitrogen found out the field emission current and the work function of the DLC-coated FEAs was remarkably decreased than that of the non-coated silicon FEAs. As nitrogen doping concentrations are increased the work function of FEAs is decreased and the field emission properties are improved in nitrogen doped DLC-coated FEAs. This phenomenon in due the fact that the Fermi energy level moves to the conduction band by increasing nitrogen doping concentration.