• 한국균학회지
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• 제50권4호
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• pp.255-262
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• 2022

In this study, the fungal strain KNUF-21-F39 was isolated from a declined apple tree (Malus domestica) in the Chungcheongbuk province in Korea. The strain KNUF-21-F39 presented a slow growth rate and a variety of macroconidia shapes and sizes ranging from ovoid to fusoid and 1- to 5-septate, primarily showing 3- and 4-septate, with "S" -shaped macroconidia rarely observed. The strain was identified based on morphological characteristics along with phylogenetic analysis performed using the internal transcribed spacer region (ITS) and partial sequences of translation elongation factor 1-α (tef1), RNA polymerase largest subunit (rpb1), and calmodulin (cal) genes. The fungal strain KNUF-21-F39 was identified as Fusarium diversisporum, which has not been previously reported in Korea. The ice nucleation activity (INA) of the strain was also evaluated, identifying the strain as positive for INA. This is the first report characterizing F. diversisporum as an IN-active fungal species.

• 한국표면공학회지
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• 제40권2호
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• pp.91-97
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• 2007

In this study we investigated the oxygen effect on the nucleation and its residual stress during unbalanced magnetron sputtering. Up to 0.5% in oxygen flow rate, cubic phase (c-BN) was dominated with extremely small fraction of Hexagonal phase (h-BN) of increasing trend with oxygen concentration, whereas hexagonal phase is dominated beyond 0.75% flow rate. Interestingly, the residual stress in cubic-phase-dominated films was substantially reduced with small amount of oxygen (${\sim}0.5%$) down to a low value comparable to the h-BN case. This may be because oxygen atoms break B-N $sp^3$ bonds and make B-O bonds more favorably, increasing $sp^2$ bonds preference, as revealed by FTIR and NEXAFS. It was confirmed by experimental facts that the threshold bias voltage for nucleation and growth of cubic phase were increased from -55 V to -70 V and from -50 V to -60 V respectively. The reduction of residual stress in O-added c-BN films is seemingly resulting from the microstructure of the films. The oxygen tends to increase slightly the amount of h-BN phase in the grain boundary of c-BN and the soft h-BN phase of 3D network including surrounding nano grains of cubic phase may relax the residual stress of cubic phase.

• 한국진공학회지
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• 제7권2호
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• pp.94-103
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• 1998

HFCVD(Hot Filament Chemical Vapor Deposition)방법을 이용한 다이아몬드의 핵 생성과 성장에 있어서, 인가한 직류 bias를 변수로 하여 핵생성 밀도와 증착율의 변화를 조 사하였다. 반응압력 20torr, 메탄농도 1.0%, Filament 온도 $2100^{\circ}C$ 그리고 Substrate 온도 $980^{\circ}C$에서 증착 단계를 핵생성기와 성장기로 구분하고 각 단계마다 bias의 방향과 크기를 다르게 인가하면서 다이아몬드 박막을 증착시켰다. Negative bias는 핵생성기에는 핵생성을 촉진시키지만 성장기에도 계속 인가하면 결정입자의 지속적인 성장을 방해하고 결정 구조를 비다이아몬드 성분으로 변화시키는 작용을 하여 박막의 morphology에 좋지 않은 영향을 주 었다. Positive bias는 핵생성기와 성장기에서 모두 $CH_4$의 분해를 촉진시킨 결과 증착율의 향상을 가져왔다. 따라서 다이아몬드 박막의 증착시 핵생성기에서는 negative bias를 인가하 고 성장기에는 positive bias를 인가하는 것이 핵생성 밀도와 증착율의 향상에 효과적인 것 으로 조사되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.78-78
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• 2013

Recently, many platinoid metals like platinum and ruthenium have been used as an electrode of microelectronic devices because of their low resistivity and high work-function. However the material cost of Ru is very expensive and it usually takes long initial nucleation time on SiO2 during chemical deposition. Therefore many researchers have focused on how to enhance the initial growth rate on SiO2 surface. There are two methods to deposit Ru film with atomic layer deposition (ALD); the one is thermal ALD using dilute oxygen gas as a reactant, and the other is plasma enhanced ALD (PEALD) using NH3 plasma as a reactant. Generally, the film roughness of Ru film deposited by PEALD is smoother than that deposited by thermal ALD. However, the plasma is not favorable in the application of high aspect ratio structure. In this study, we used a bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] as a metal organic precursor for both thermal and plasma enhanced ALDs. In order to reduce initial nucleation time, we use several methods such as Ar plasma pre-treatment for PEALD and usage of sacrificial RuO2 under layer for thermal ALD. In case of PEALD, some of surface hydroxyls were removed from SiO2 substrate during the Ar plasma treatment. And relatively high surface nitrogen concentration after first NH3 plasma exposure step in ALD process was observed with in-situ Auger electron spectroscopy (AES). This means that surface amine filled the hydroxyl removed sites by the NH3 plasma. Surface amine played a role as a reduction site but not a nucleation site. Therefore, the precursor reduction was enhanced but the adhesion property was degraded. In case of thermal ALD, a Ru film was deposited from Ru precursors on the surface of RuO2 and the RuO2 film was reduced from RuO2/SiO2 interface to Ru during the deposition. The reduction process was controlled by oxygen partial pressure in ambient. Under high oxygen partial pressure, RuO2 was deposited on RuO2/SiO2, and under medium oxygen partial pressure, RuO2 was partially reduced and oxygen concentration in RuO2 film was decreased. Under low oxygen partial pressure, finally RuO2 was disappeared and about 3% of oxygen was remained. Usually rough surface was observed with longer initial nucleation time. However, the Ru deposited with reduction of RuO2 exhibits smooth surface and was deposited quickly because the sacrificial RuO2 has no initial nucleation time on SiO2 and played a role as a buffer layer between Ru and SiO2.

• 한국세라믹학회지
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• 제42권9호
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• pp.599-601
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• 2005

The coarsening process of two different $BaTiO_3$ single crystal seeds, one with a (111) double twin and the other without it, was investigated. Due to the presence of Twin Plane Reentrant Edge (TPRE), the coarsening rate of the twinned seed crystal was significantly higher than that without a twin. For the coarsening by the 2-dimensional nucleation and lateral growth, the energy barrier for nucleation at the TPRE was analyzed to be about a half compared with that at the terrace planes.

• 태양에너지
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• 제1권1호
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• pp.30-36
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• 1981

Pool Boiling heat transfer from controlled arrays of artificial nucleation sites was studied experimentally. Distilled water were boiled from artificial sites of uniform size, shape and spacing, drilled in superfinished copper horizontal surfaces at site density of 16, 25, 36, 49, 64, 81, 100 per $2.25cm^2$. The results confirm the boiling heat transfer from artificial sites can be improved by increasing the site density N/A or temperature difference ${\Delta}T$ or both. Following experimental correlation were developed for predicting the heat transfer rate from the heating surface which has artificial sites. $$q/A = C(T_s - T_{sat})^{1.811}(N/A)^{0.41}$$

• 한국주조공학회지
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• 제6권4호
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• pp.269-276
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• 1986

The effects of Se, $CaCO_3$ and CaO addition on the first stage graphization of malleable iron were evaluated. The results obtained in this work were as follows. 1. Many gas bubbles were found in the white cast iron under Se, $CaCO_3$ addition. 2. Nodular graphite were formed by annealing of the white cast iron with remained gas bubbles. 3. When specimens were annealed, bubbles provided the nucleation sites that were needed in graphite precipitation, so the nucleation rate of graphite was increased. 4. The remained gas bubbles and defects were more effective for the graphitization than metallic compounds.

• Tribology and Lubricants
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• 제11권5호
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• pp.20-25
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• 1995

Diamond films were prepared by a hot filament vapor deposition onto polycrystal silicon nitride substrates. Different kinds of silicon nitride containing CaO and $Fe_{2}O_{3}$ were manufactured to investigate the impurity effect of substrate on the morphology of diamond films and their wear behaviors. Nucleation rates and morphologies of diamond films deposited on various kinds of silicon nitride were compared. The highest nucleation rate was observed in a substrate containing 1% of CaO. Wear tests were performed with a silicon nitride ball on the disk geometry to investigate the tribological behavior of diamond film against silicon nitride. This study demonstrated that different morphologies of diamond film due to substrate impurities produced different wear behavior against silicon nitride.

• 한국표면공학회지
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• 제41권2호
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• pp.48-50
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• 2008

Solid phase crystallization (SPC) of amorphous silicon is usually conducted at around $600^{\circ}C$ since it is used in the application of flat panel display using thermally susceptible glass substrate. In this study we conducted SPC experiments at temperatures higher than $600^{\circ}C$ using silicon wafers. Crystallization rate becomes dramatically rapid at higher temperatures since SPC kinetics is controlled by nucleation with high value of activation energy. We report SPC kinetics of high temperatures compared to that of low temperatures.

• 한국세라믹학회지
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• 제31권3호
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• pp.249-256
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• 1994

By surface structure and X-ray topographic observation, growth mechanism of NAB single crystal grown by TSSG technique using a BaB4O7 flux was studied. Surface structure of grown crystals were investigated by optical microscope. Growth history and crystal defects included within grown crystal were investigated using X-ray topography. The {001} faces were grown by 2-D nucleation growth. As decreasing cooling rate, growth mechanism of {111} and {11} was changed from 2-D nucleation growth to the growth by screw dislocation. Only surface striations developed parallel to a-axis were observed on {010} faces. Growth sector of NAB crystals were divided into {001}, {111}, {010}, {021}, {11}. The inclusion which was usually trapped between {001} faces was investigated.