• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.418-418
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• 2012

Synthesis of nanocrystalline diamond powder was investigated via a gas-to-particle scheme using the hot filament chemical vapor deposition. Effect of substrate surface seeding by nano diamond powder, and that of the electrical conductance of the substrate were studied. The substrate temperature, methane content in the precursor gas, filament-substrate distance and filament temperature were $670^{\circ}C$, 5% methane in hydrogen, 10 mm and $2400^{\circ}C$, respectively. The powder formation by gas-to-particle mechanism were greatly enhanced by the substrate seeding by the nano diamond powder. It was attributed to the removal of the electrostatic force between the substrate and the seeded nano diamond particle by the thermal electron shower from the hot filament, via the depolarization of the substrate surface or the attached diamond powder and subsequent levitation into the gas phase to serve as the gas-phase nucleation site. The powder formation was greatly favoured by the conducting substrate relative to the insulating substrate, which proved the actual effect of the electric static force in the powder formation.

• 한국결정성장학회지
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• 제23권2호
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• pp.86-92
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• 2013

나노결정질 다이아몬드 박막 증착을 위한 전처리 공정으로 $SF_6/O_2$ 유도결합 플라즈마를 이용하여 Si 기판 표면을 texturing하였다. $SF_6/O_2$ 플라즈마 texturing은 2~16 범위의 매우 넓은 정규화된 표면 조도 선택성을 제공할 수 있음을 확인하였다. Texturing된 Si 기판 표면의 나노 다이아몬드 입자 seeding 이후 기존 기계적 연마 전처리에 비해 현저히 향상된 ${\sim}6.5{\times}10^{10}cm^{-2}$의 높은 핵형성 밀도를 확보하였다.

• 한국표면공학회지
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• 제34권5호
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• pp.448-454
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• 2001

Low field electron emission from novel carbon based cold cathodes is reported. The cathodes consisted of a layer of nanoseeded diamond and an over layer of nanocluster carbon films. The nanoseeded diamond was first coated on to thesubstrate. The nanocluster carbon films were then deposited on the nanocrystalline diamond coated substrates using the cathodic arc process at room temperature. The heterostructured microcathodes were observed to exhibit electron emission currents of 1 $\mu$A/cm$^2$ at fields as low as 1.5 to 2V/$\mu$m. The effect of the nanoseeded diamond size and concentration and the properties of different nanocluster carbon films on emission characteristics is presented.

• 한국표면공학회지
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• 제47권5호
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• pp.263-268
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• 2014

Nanocrystalline diamond(NCD) coated SiC balls were applied in a ball-on-disk tribometer. After seeding in an ultrasonic bath containing nanometer diamond powders, $2.2{\mu}m$ thick NCD films were deposited on sintered 3 mm diameter SiC balls at $600^{\circ}C$ in a 2.45 GHz microwave plasma CVD system. Bare $ZrO_2$ and SiC balls were prepared for comparison as test balls. Tribology tests were performed in air with pairs of three different balls and mirror polished steel(SKH51) disk. The wear tracks on balls and disks were examined by optical microscope and alpha step profiler. Under the load of 3 N, the friction coefficients of steel against $ZrO_2$, SiC and NCD-coated balls were between 0.4 and 0.8. After a few thousands sliding laps, the friction coefficient of NCD-coated balls dropped from 0.45 to below 0.1 and maintained thereafter. Under a higher load of 10 N or 20 N with a long sliding distance of 2 km, $ZrO_2$ and SiC balls exhibited the similar friction coefficients as above. The friction coefficient of NCD-coated balls was less than 0.1 from the beginning and increased to above 0.1 steadily or with some fluctuations as sliding distance increased. NCD coating layers were found worn out after long duration and/or high load sliding test, which resulted in the friction coefficient higher than 0.1.

• 한국표면공학회지
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• 제46권2호
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• pp.68-74
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• 2013

For the coating of diamond films on WC-Co tools, a buffer interlayer is needed because Co catalyzes diamond into graphite. W and Ti were chosen as candidate interlayer materials to prevent the diffusion of Co during diamond deposition. W or Ti interlayer of $1{\mu}m$ thickness was deposited on WC-Co substrate under Ar in a DC magnetron sputter. After seeding treatment of the interlayer-deposited specimens in an ultrasonic bath containing nanometer diamond powders, $2{\mu}m$ thick nanocrystalline diamond (NCD) films were deposited at $600^{\circ}C$ over the metal layers in a 2.45 GHz microwave plasma CVD system. The cross-sectional morphology of films was observed by FESEM. X-ray diffraction and visual Raman spectroscopy were used to confirm the NCD crystal structure. Micro hardness was measured by nano-indenter. The coefficient of friction (COF) was measured by tribology test using ball on disk method. After tribology test, wear tracks were examined by optical microscope and alpha step profiler. Rockwell C indentation test was performed to characterize the adhesion between films and substrate. Ti and W were found good interlayer materials to act as Co diffusion barriers and diamond nucleation layers. The COFs on NCD films with W or Ti interlayer were measured as less than 0.1 whereas that on bare WC-Co was 0.6~1.0. However, W interlayer exhibited better results than Ti in terms of the adhesion to WC-Co substrate and to NCD film. This result is believed to be due to smaller difference in the coefficients of thermal expansion of the related films in the case of W interlayer than Ti one. By varying the thickness of W interlayer as 1, 2, and $4{\mu}m$ with a fixed $2{\mu}m$ thick NCD film, no difference in COF and wear behavior but a significant change in adhesion was observed. It was shown that the thicker the interlayer, the stronger the adhesion. It is suggested that thicker W interlayer is more effective in relieving the residual stress of NCD film during cooling after deposition and results in stronger adhesion.

• 한국표면공학회지
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• 제46권4호
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• pp.145-152
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• 2013

The growth behavior of nanocrystalline diamond (NCD) film has been studied for three different substrates, i.e. bare Si wafer, 1 ${\mu}m$ thick W and Ti films deposited on Si wafer by DC sputter. The surface roughness values of the substrates measured by AFM were Si < W < Ti. After ultrasonic seeding treatment using nanometer sized diamond powder, surface roughness remained as Si < W < Ti. The contact angles of the substrates were Si ($56^{\circ}$) > W ($31^{\circ}$) > Ti ($0^{\circ}$). During deposition in the microwave plasma CVD system, NCD particles were formed and evolved to film. For the first 0.5h, the values of NCD particle density were measured as Si < W < Ti. Since the energy barrier for heterogeneous nucleation is proportional to the contact angle of the substrate, the initial nucleus or particle densities are believed to be Si < W < Ti. Meanwhile, the NCD growth rate up to 2 h was W > Si > Ti. In the case of W substrate, NCD particles were coalesced and evolved to the film in the short time of 0.5 h, which could be attributed to the fact that the diffusion of carbon species on W substrate was fast. The slower diffusion of carbon on Si substrate is believed to be the reason for slower film growth than on W substrate. The surface of Ti substrate was observed as a vertically aligned needle shape. The NCD particle formed on the top of a Ti needle should be coalesced with the particle on the nearby needle by carbon diffusion. In this case, the diffusion length is longer than that of Si or W substrate which shows a relatively flat surface. This results in a slow growth rate of NCD on Ti substrate. As deposition time is prolonged, NCD particles grow with carbon species attached from the plasma and coalesce with nearby particles, leaving many voids in NCD/Ti interface. The low adhesion of NCD films on Ti substrate is related to the void structure of NCD/Ti interface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.180-180
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• 2016

보론이 도핑된 $3{\times}3cm$ 크기의 p 형 다결정 실리콘 기판의 표면을 경면연마한 후, 다이아몬드 입자의 seeding을 위해 슬러리 중 다이아몬드 분말의 입도를 5 nm로 고정하고 초음파 전처리 공정을 진행한 후, 다이아몬드 박막을 증착하였다. 다이아몬드 증착은 Microwave Plasma Chemical Vapor Deposition 장비를 이용하였으며, 공정 조건은 초기 진공 $10{\times}10^{-3}Torr$, 공정 가스 비율 $Ar:CH_4=200:2$, 가스 유량 202 sccm, 공정압력 90 Torr, 마이크로웨이브 파워 600 W, 기판 온도 $600^{\circ}C$이었다. 기판에 DC bias 전압을 인가하는 것을 공정 변수로 하여 0, -50, -100, -150, -200 V로 변화시켜가며, 0.5, 1, 2, 4 h 동안 증착을 진행하였다. 주사전자현미경과 XRD, AFM, 접촉각 측정 장비를 이용하여 증착된 다이아몬드 입자와 막의 특성을 분석하였다. 각 bias 조건에서 초기에는 다이아몬드 입자가 형성되어 성장되었다가 시간이 증가될수록 연속적인 다이아몬드 막이 형성되었다. Table 1은 각 bias 조건에서 증착 시간을 4 h까지 변화시키면서 얻은 다이아몬드 입자 또는 박막의 높이(두께)를 나타낸 것이다. 2 h까지의 공정 초기에는 bias 조건의 영향을 파악하기 어려운데, 이는 bias에 의한 과도한 이온포격으로 입자가 박막으로의 성장에 저해를 받는 것으로 사료된다. 증착시간이 4 h가 경과하면서 -150 V 조건에서 가장 두꺼운 막이 성장되었다. 이는 기판 표면을 덮은 다이아몬드 박막 위에서 이차 핵생성이 bias에 의해 촉진되기 때문으로 해석된다. -200 V의 조건에서는 오히려 막의 성장이 더 느렸는데, 이는 Fig. 1에 보이듯이 과도한 이온포격으로 Si/diamond 계면에서 기공이 형성된 것과 연관이 있는 것으로 보인다.

• 한국결정성장학회지
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• 제23권6호
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• pp.291-295
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• 2013

산화 및 수소 분위기 열처리를 통한 화학적 표면 개질로 나노다이아몬드 seed 입자의 응집성 완화 및 초미세나노결정질 다이아몬드 (UNCD) 박막 증착을 위한 핵형성 밀도 향상을 확보하였다. 열처리에 의해 나노다이아몬드 seed 입자표면 작용기가 개질되었고, 제타 전위도 증가하였다. 또한, 응집체 평균 크기가 약 $2{\mu}m$에서 ~55 nm로 크게 감소하였다. $600^{\circ}C$, 수소 열처리된 seed 입자로 seeding 한 Si 기판으로부터 열처리하지 않은 seed 입자에 비해 현저하게 향상된 ${\sim}2.7{\times}10^{11}cm^{-2}$의 매우 높은 핵형성 밀도를 확보하였다.