• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.505-509
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• 2016

We have investigated the characteristics of amorphous silicon (a-Si) thin-film solar cell by inserting barrier layer. The conversion efficiency of a-Si thin-film solar cells on graphite substrate shows nearly zero because of the surface roughness of the graphite substrate. To enhance the performance of solar cells, the surface morphology of the back side were modified by changing the barrier layer on graphite. The surface roughness of graphite substrate with the barrier layer grown by plasma enhanced chemical vapor deposition (PECVD) reduced from ~2 um to ~75 nm. In this study, the combination of the barrier layer on graphite substrate is important to increase solar cell efficiency. We achieved ~ 7.8% cell efficiency for an a-Si thin-film solar cell on graphite substrate with SiNx/SiOx stack barrier layer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.421.2-421.2
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• 2014

We report on the growth of ZnO nanorods (NRs) grown on graphite and silicon substrates via an all-solution process and characteristics of their heterojunctions. Structural investigations indicated that morphological and crystalline properties were not significantly different for the ZnO NRs on both substrates. However, optical properties from photoluminescence spectra showed that the ZnO NRs on graphite substrate contained more point defects than that on Si substrate. The ZnO NRs on both substrates showed typical rectification properties exhibiting successful diode formation. The heterojunction between the ZnO NRs and the graphite substrate showed a Schottky diode characteristic and photoresponse under ultraviolet illumination at a small reverse bias of -0.1 V. The results showed that the graphite substrate could be a good candidate for a Schottky contact electrode as well as a conducting substrate for electronic and optoelectronic applications of ZnO NRs.

• 한국세라믹학회지
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• 제50권2호
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• pp.122-126
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• 2013

The surface roughness of the inner and outer surfaces of a tube is an important requirement for nuclear fuel cladding. When an inner SiC clad tube, which is considered as an advanced Pressurized Water Cooled Reactor (PWR) clad with a three-layered structure, is fabricated by Chemical Vapor Deposition (CVD), the surface roughness of the substrate, graphite, is an important process parameter. The surface character of the graphite substrate could directly affect the roughness of the inner surface of SiC deposits, which is in contact with a substrate. To evaluate the effects of the surface roughness changes of a substrate, SiC deposits were fabricated using different types of graphite substrates prepared by the following four polishing paths and heat-treatment for purification: (1) polishing with #220 abrasive paper (PP) without heat treatment (HT), (2) polishing with #220 PP with HT, (3) #2400 PP without HT, (4) polishing with #2400 PP with HT. The average surface roughnesses (Ra) of each deposited SiC layer are 4.273, 6.599, 3.069, and $6.401{\mu}m$, respectively. In the low pressure SiC CVD process with a graphite substrate, the removal of graphite particles on the graphite surface during the purification and the temperature increasing process for CVD seemed to affect the surface roughness of SiC deposits. For the lower surface roughness of the as-deposited interlayer of SiC on the graphite substrate, the fine controlled processing with the completed removal of rough scratches and cleaning at each polishing and heat treating step was important.

• 한국세라믹학회지
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• 제34권12호
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• pp.1199-1204
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• 1997

SiC conversion layer was fabricated by the chemical vapor reaction between graphite substrate and silica powder. The CVR process was carried out in nitrogen atmosphere at 175$0^{\circ}C$ and 185$0^{\circ}C$. From the reduction of silica powder with graphite substrate, the SiO vapor was created, infiltrated into the graphite substrate, then, the SiC conversion layer was formed from the vapor-solid reaction of SiO and graphite. In the XRD pattern of conversion layer, it was confirmed that 3C $\beta$-SiC phase was created at 175$0^{\circ}C$ and 185$0^{\circ}C$. Also, in the back scattered image of cross-sectional conversion layer, it was found that the conversion layer was easily formed at 185$0^{\circ}C$, the interface of graphite substrate and SiC layer was observed. It was though that the coke particle size and density of graphite substrate mainly affect the XRD pattern and microstructure of SiC conversion layer. In the oxidation test of 100$0^{\circ}C$, the SiC converted graphites exhibited good oxidation resistance compared with the unconverted graphites.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1120-1128
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• 2004

The SCBFC was composed of bilayered cathode, the outside of which was modified with $Fe^{3+}$ (graphite-Fe(III) cathode) and the inside of which was porcelain membrane, and of an anode which was modified with $Mn^{4+}$ (graphite­Mn(lV) anode). The graphite-Fe(III), graphite-Mn(IV), and porcelain membrane were designed to have micropores. The outside of the cathode was exposed to the atmosphere and the inside was contacted with porcelain membrane. In all SCBFCS the graphite-Fe(III) was used as a cathode, and graphite-Mn(IV) and normal graphite were used as anodes, for comparison of the function between normal graphite and graphite-Mn(IV) anode. The potential difference between graphite-Mn(IV) anode and graphite-Fe(III) cathode was about 0.3 volt, which is the source for the electron driving force from anode to cathode. In chemical fuel cells composed of the graphite-Mn(IV) anode and graphite-Fe(III) cathode, a current of maximal 13 mA was produced coupled to oxidation of NADH to $NAD^{+}$ the current was not produced in SCBFC with normal graphite anode. When growing and resting cells of E. coli were applied to the SCBFC with graphite-Mn(IV) anode, the electricity production and substrate consumption were 6 to 7 times higher than in the SCBFC with normal graphite anode, and when we applied anaerobic sewage sludge to SCBFC with graphite-Mn(IV) anode, the electricity production and substrate consumption were 3 to 5 times higher than in the SCBFC with normal graphite anode. These results suggest that useful electric energy might possibly be produced from SCBFC without electron mediators, electrode-active bacteria, and extra energy consumption for the aeration of catholyte, but with wastewater as a fuel.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.36-37
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• 1992

• 한국세라믹학회지
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• 제36권1호
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• pp.21-29
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• 1999

흑연 기판에 탄화규소 전환층을 형성하는데 있어서 기판의 밀도와 기공 크기 분포의 영향이 조사되었다. 전환층형성을 위한 화학 반응은 기판의 표면 또는 표면 하부에서 SiO 기체의 침투를 통해 이루어졌다. 전환 공정 동안 기판 표면에서의 충분한 양의 SiO 기체 침투 및 연속적인 화학반응에 요구되는 기공크기 분포는 1.0~10.0$\mu\textrm{m}$ 범위인 것으로 추정되엇다. 유한요소법에 의한 탄화규소 층의 응력 해석에서는 열적 불일치에 기인하는 잔류응력 분포를 나타냈다. 그러나. X-선 회절에 의해 탄화규소 층에서는 압축응력이 측정되었으며, 탄화규소 층에서의 잔류응력 분포에 대해 SiC 층과 흑연 기판간의 interlayer의 constraining 효과, 전환층의 치밀화 거동 및 입자성장에 의해 주로 영향받는 것으로 추정되었다.

• 한국세라믹학회지
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• 제38권9호
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• pp.846-852
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• 2001

2차원적 몬테 칼로 시뮬레이션을 사용하여, 화학적 기상 반응법에 의한 탄화규소 전환층의 생성에 미치는 온도의 영향을 조사하였다. 화학적 기상 반응법은 실리카의 열탄화 환원법에 근거하며, 흑연 기판의 탄소와 실리카 반응기체와의 화학적 반응에 의하여 탄화규소 전환층을 형성하는 방법이다. 탄화규소는 반응기체의 확산 및 반응과 같은 열적활성화 과정을 통하여 생성되기 때문에 탄화규소 전환층의 형성은 온도에 크게 의존함을 알 수 있다. 본 연구에서는 몬테 칼로법을 사용하여 삼각격자로 배열된 2차원적인 계에서 흑연 기판의 미세 기공을 따라 확산된 반응기체와 탄소와의 반응에 의해서 탄화규소가 형성되는 과정을 시뮬레이션을 행하였다. 반응 온도를 1900K, 2000K, 2100K, 2200K로 조건을 달리하여 시뮬레이션 하였으며, 그 계산 결과를 실험 결과와 비교하여 재현성을 검토하고 탄화규소 전환층의 두께와 화학적 조성 구배에 대한 반응 온도의 영향을 검증하기 위한 것이다.

• 한국결정성장학회지
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• 제23권5호
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• pp.213-217
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• 2013

GaN는 대표적인 III-V족 질화물반도체로 주로 값싸고 다루기 쉬운 사파이어 기판 위에 성장된다. 하지만 사파이어 기판은 부도체이며, GaN과의 격자부정합을 일으키고 열전도도 또한 낮은 기판으로 알려져 있다. 본 논문에서는 방열기능과 열 전기전도도가 뛰어난 금속 화합물 탄소체 기판 위에 poly GaN epilayer를 HVPE법으로 성장시켜보았다. 비정질의 금속 화합물 탄소체 기판위에 성장되는 GaN epilayer의 성장메카니즘을 관찰하였다. GaN epilayer의 성장을 위해 HCl과 $NH_3$를 흘려주었다. 성장하기 위해 source zone과 growth zone의 온도는 각각 $850^{\circ}C$와 $1090^{\circ}C$로 설정했다. 성장이 끝난 샘플은 SEM, EDS, XRD측정을 통해 분석하였다.

• 한국재료학회지
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• 제29권5호
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• pp.317-321
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• 2019

We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.