• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.274-274
• /
• 2014

금속칼코게나이드 화합물중 하나인 $MoS_2$는 초저 마찰계수의 금속성 윤활제로 널리 사용되고 있으며 흑연과 비슷한 판상 구조를 지니고 있어 기계적 박리법을 통한 그래핀의 발견 이후 2차원 박막 합성법에 대한 활발한 연구가 진행되고 있다. 최근 다양한 응용이 진행 중인 그래핀의 경우 높은 전자이동도, 기계적 강도, 유연성, 열전도도 등 뛰어난 물리적 특성을 지니고 있으나 zero-bandgap으로 인한 낮은 on/off ratio는 thin film transistor (TFT), 논리회로(logic circuit) 등 반도체 소자 응용에 한계가 있다. 하지만 $MoS_2$는 벌크상태에서 약 1.2 eV의 indirect band-gap을 지닌 반면 단일층의 경우 1.8 eV의 direct-bandgap을 나타내고 있다. 또한 단일층 $MoS_2$를 이용하여 $HfO_2/MoS_2/SiO_2$ 구조의 트랜지스터를 제작하였을 때 $200cm^2/v^{-1}s^{-1}$의 높은 mobility와 $10^8$ 이상의 on/off ratio 나타낸다는 연구가 보고되어 있어 박막형 트랜지스터 응용을 위한 신소재로 주목을 받고 있다. 한편 2차원 $MoS_2$ 박막을 합성하기 위한 대표적인 방법인 기계적 박리법의 경우 고품질의 단일층 $MoS_2$ 성장이 가능하지만 대면적 합성에 한계를 지니고 있으며 화학기상증착법(CVD)의 경우 공정 gas의 분해를 위한 높은 온도가 요구되므로 박막형 투명 트랜지스터 응용을 위한 플라스틱 기판으로의 in-situ 성장이 어렵기 때문에 이를 보완할 수 있는 $MoS_2$ 박막 합성 공정 개발이 필요하다. 특히 Plasma enhanced chemical vapor deposition (PECVD) 방법은 공정 gas가 전기적 에너지로 분해되어 chamber 내부에서 cold-plasma 형태로 존 재하기 때문에 박막의 저온성장 및 대면적 합성이 가능하며 고진공을 바탕으로 합성 중 발생하는 오염 요소를 효과적으로 제어할 수 있다. 본 연구에서는PECVD를 이용하여 plasma power, 공정압력, 공정 gas의 유량 등 다양한 공정 변수를 조절함으로써 저온, 저압 조건하에서의 $MoS_2$ 박막 성장 가능성을 확인하였으며 전구체로는 Mo 금속과 $H_2S$ gas를 사용하였다. 또한 향후 flexible 소자 응용을 위한 플라스틱 기판의 녹는점을 고려하여 공정 온도는 $300^{\circ}C$ 이하로 설정하였으며 합성된 $MoS_2$ 박막의 두께 및 화학적 구성은 Raman spectroscopy를 이용하여 확인 하였다. 공정온도 $200^{\circ}C$와 $150^{\circ}C$에서 성장한 $MoS_2$ 박막의 Raman peak의 경우 상대적으로 낮은 공정온도로 인하여 Mo와 H2S의 화학적 결합이 감소된 것을 관찰할 수 있었고 $300^{\circ}C$의 경우 약 $26{\sim}27cm^{-1}$의 Raman peak 간격을 통해 5~6층의 $MoS_2$ 박막이 형성 된 것을 확인할 수 있었다.

• Journal of the Korean Vacuum Society
• /
• v.20 no.2
• /
• pp.155-163
• /
• 2011

Carbon nanotubes (CNT) have been attracted much attention since they have been expected to be used in various areas by virtue of their outstanding physical, electrical, and chemical properties. In order to make full use of their prominent electric conductivity in some areas such as electron emission sources, device interconnects, and electrodes in energy storage devices, direct growth of CNT with vertical alignment is definitely beneficial issue because they can maintain mechanical stability and high conductivity at the interface between substrates. Here, we report direct growth of vertically aligned CNT (VCNT) on Cu foils using thermal chemical vapor deposition and characterize the field emission property of the VCNT. The VCNT's height was controlled by changing the growth temperature, growth time, and catalytic layer thickness. Optimum growth condition was found to be $800^{\circ}C$ for 20 min with acetylene and hydrogen mixtures on Fe catalytic layer of 1 nm thick. The diameter of VCNT grown was smaller than that of usual multi walled CNT. Based on the result of field emission characterization, we concluded that the VCNT on Cu foils can be useful in various potential applications where high conductivity through the interface between CNT and substrate is required.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.36T no.3
• /
• pp.13-18
• /
• 1999

Diamond film was deposited on Si wafer using $\textrm{H}_2$ and $\textrm{CH}_4$ mixed gas by RF PACVD. Prior to deposition, mechanical scratching was done to improve density of nucleation sites with diamond paste of $1\mu\textrm{m}$ The microstructure of deposited film was studied at various methane concentrations. The deposited film was characterized by XRD(X-tay diffraction), SEM(Scanning Electron Microscopy) and Raman Spectroscopy The deposited diamond film showed that the crystallite was increased at the lower methane concentration.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.122-122
• /
• 2003

1991년 일본 NEC의 Iijima가 탄소 나노튜브를 발견한 이후, 1995년 Smalley와 De Heer에 의해 탄소 나노튜브의 우수한 전폐방출 특성이 보고되면서 탄소 나노튜브를 새로운 전계방출 물질로 응용하기 위한 연구가 세계적으로 활발히 진행되고 있다. 탄소 나노튜브의 전계방출 연구는 대부분 시장규모가 클 것으로 예상되는 field emission display(FEED)의 cathode에 집중되고 있다. FED cathode는 현재 탄소 나노튜브 페이스트를 스크린 프린팅하여 대면적화를 이루고자 하는 방향과 탄소 나노튜브를 기판 위에 chemical vapor deposition(CVD)로 증착하여 고정세화와 저전압 구동을 이루고자 하는 방향으로 진행되고있다.

• Electrical & Electronic Materials
• /
• v.9 no.5
• /
• pp.470-475
• /
• 1996

Fiber-textured diamond films have been deposited on scratched silicon(100) substrate by micro wave .plasma enhanced chemical vapor deposition at the condition of micro wave power : 950 W, pressure : 60 torr, H$_{2}$ gas flow rate : 50 sccm, CH$_{4}$ gas flow rate : 1.5 sccm, substrate temperature : about 900.deg. C and deposition time : 20 hours. The films were characterized by mean of scanning electron microscopy, Raman spectroscopy and X-ray analysis.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.856-857
• /
• 1998

Hydrogenated amorphous carbon nitride [a-C:H(N)] films were deposited on pretreated silicon(100) substrate in activated gas phase using. RF plasma-assisted CVD. We measured the FT-IR spectrum to investigate $C{\equiv}N$ stretching mode(nitrile), C-H stretching mode, C-H bending mode, C=C stretching mode C=N(imino) mode, and the EDX to investigate the ratio of N to C(0.25). By the results of FT-IR and EDX spectrum, We confirmed that hydrogenated amorphous carbon nitride films successfully were synthesized by RF-PACVD

• Journal of the Korean Ceramic Society
• /
• v.29 no.9
• /
• pp.681-688
• /
• 1992

Ultrafine Si3N4 and Si3N4+SiC mixed powders were synthesized through thermal plasma chemical vapor deposition(CVD) using a hybrid plasma, which was characterized by the supersposition of a radio-frequency plasma and arc jet. The reactant SiCl4 was injected into an arc jet and completely decomposed in a hybrid plasma, and the second reactant CH4 and/or NH3 mixed with H2 were injected into the tail flame through double stage ring slits. In the case of ultrafine Si3N4 powder synthesis, reaction efficiency increased significantly by double stage injection compared to single stage one, although crystallizing behaviors depended upon injection speed of reactive quenching gas (NH3+N2) and injection method. For the preparation of Si2N4+SiC mixed powders, N/C composition ratio could be controlled by regulating the injection speed of NH3 and/or CH4 reactant and H2 quenching gas mixtures as well as by adjusting the reaction space.

• Journal of the Korean Ceramic Society
• /
• v.32 no.6
• /
• pp.685-696
• /
• 1995

The most important techniques in the synthesis of SiC/C function gradient material (FGM) are to control the SiC/C ratio and to obtain the moderate deposition rate. For these, various gas systems and flow rates were attempted and evaluated. It turned out that the CH4＋SiCl4＋H2 system was suitable for the deposition of SiC-rich layers, the C3H8＋SiCl4＋Ar system for the deposition of carbon-rich layers, and the C3H8＋SiCl4＋H2＋Ar system was good to deposit the layers between them.

• Proceedings of the KIEE Conference
• /
• 1998.07d
• /
• pp.1514-1515
• /
• 1998

Diamond thin films were deposited on n-type (100) Si wafers from $H_2-CH_4$ gas mixture by rf PACVD. Prior to deposition, mechanical scratching was done to improve density of nucleation sites with diamond paste of 3${\mu}m$. The microstructure of deposited diamond thin films was studied by using the following conditions : discharge power of 500W, $H_2$ flow rate of 50sccm, reaction pressure of 20torr, and $CH_4/H_2$ ratio of 0.3$\sim$1%. The deposited diamond thin films showed that the crystallite was increased at the lower methane concentration. The deposited thin films were characterized by Scanning Electron Microscopy. Raman Spectroscopy and Fourier-Transform Infrared Spectroscopy.

• Journal of the Microelectronics and Packaging Society
• /
• v.11 no.1
• /
• pp.59-64
• /
• 2004

The performance of fuel cell electrode depends on the characteristics of the catalyst support material. This paper deals with the use of CNF(carbon nanofibre) and CNT(carbon nanotube) as platinum catalyst support. The CNF and CNT were synthesized with catalyst treated by mechanochemical process and were prepared by chemical vapor deposition (CVD) method. The platinum supported on CNF and CNT for polymer electrolyte membrane fuel cell (PEMFC) application. In result, the best I-V characteristic was verified by the prepared MEA(membrane electrode assembly) from twisted CNF that had a diameter of 65 nm.