• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.16-23
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• 1999

Deposition of parylene (PA) films has been explored at substrate temperatures below 2$0^{\circ}C$ and pressures below 4 torr. The film thickness was measured using AFM and the film thickness measured was 3,500-12,000$\AA$ and the growth rate was 20-70$\AA$/min. T도 dielectric constant of the deposited PA films was found to be 2.66 and the dielectric strength was in excess of 2$\times$105V/cm. The growth rate became a maximum at a precursor decomposition temperature of $600^{\circ}C$. It was found that the growth rate decreased with increasing substrate temperature, whereas it increased with increasing pressure. At a precursor decomposition temperature of 75$0^{\circ}C$ or at a deposition pressure above 1 Torr the film surface became rough due to particle formation in the gas phase. The condensation of a p-xylylene monomer on the substrate surface turned out to be a rate-limiting step in the growth of the PA films.

• 한국세라믹학회지
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• 제31권1호
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• pp.88-96
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• 1994

Hot filament-assisted CVD was carried out to deposit diamond films on Si(100) substrate at 90$0^{\circ}C$ using a 1% CH4-H2 mixture gas. Deposition was made at various conditions of mass flow rate of the feed gas (30~1000 sccm), pressure (2.5~300 Torr), and filament-substrate distance (4~15 mm), and the deposited films were characterized by SEM, XRD, and Raman spectroscopy. As the flow rate increases, the growth rate also increased but the crystallinity of the film was degraded. A longer filament-substrate distance simply caused both the growth rate and the crystallinity to become poorer. On the other hand, the pressure variation resulted in a maximum growth rate of 2.6 ${\mu}{\textrm}{m}$/hr at 10 Torr and the best film quality around 50 Torr, exhibiting an optimum condition. The observed trends were interpreted in terms of the flow velocity-dependent pyrolysis reaction efficiency and mass transport through the boundary layer.

• 한국재료학회지
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• 제27권11호
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• pp.609-616
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• 2017

We investigated a Leidenfrost effect in the growth of ZnO nanostructures on silicon substrates by ultrasonic-assisted spray pyrolysis deposition(SPD). Structural and optical properties of the ZnO nanostructures grown by varying the growth parameters, such as substrate temperature, source concentration, and suction rate of the mist in the chambers, were investigated using field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence spectrum analysis. Structural investigations of the ZnO nanostructures showed abnormal evolution of the morphologies with variation of the substrate temperatures. The shape of the ZnO nanostructures transformed from nanoplate, nanorod, nanopencil, and nanoprism shapes with increasing of the substrate temperature from 250 to $450^{\circ}C$; these shapes were significantly different from those seen for the conventional growth mechanisms in SPD. The observed growth behavior showed that a Leidenfrost effect dominantly affected the growth mechanism of the ZnO nanostructures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.36-37
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• 2006

Both negative and positive substrate bias effects on the structural properties and field-emission characteristics are investigated. carbon nanotubes (CNTs) are grown on Ni catalysts employing an inductively-coupled plasma chemical vapor deposition (ICP-CVD) method. Characterization using various techniques, such as field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and Raman spectroscopy, shows that the physical dimension as well as the crystal quality of CNTs grown can be changed and controlled by the application of substrate bias during CNT growth. It is for the first time observed that the prevailing growth mechanism of CNTs, which is either due to tip-driven growth or based-on-catalyst growth, may be influenced by substrate biasing. It is also seen that negative biasing would be more effectively role in the vertical-alignment of CNTs compared to positive biasing. However, the CNTs grown under the positively bias condition display much better electron emission capabilities than those grown under negative bias or without bias. The reasons for all the measured data regarding the structural properties of CNTs are discussed to confirm the correlation with the observed field-emissive properties.

• 인간식물환경학회지
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• 제24권5호
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• pp.499-507
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• 2021

Background and objective: This study was carried out to develop an effective technique for raising seedlings of Veronica pyrethrina Nakai, a native plant species in the Korean Peninsula, in plug trays. Methods: To investigate the optimum plug cell size and sowing media, we sowed seed in to plug trays with 34, 21, and 10 mL cells and filled with a commercial horticultural substrate and mixtures of peatmoss and perlite in 1:1, 3:1, and 4:1 ratios. Fertilization levels were set at 0, 500, 1000 and 2000 mg·L^-1. Results: Plug cell size did not significantly influence the seedling growth of V. pyrethrina. By substrate type, the growth rate was highest in the horticultural substrate, followed by 4:1, 3:1, and 1:1. Growth by fertilization level was higher in all fertilized treatment groups than in the control group, and there was no difference among 500, 1000, and 2000 mg·L^-1. Conclusion: The results of this study proved that it is most suitable for raising seedlings of V. pyrethrina to sow the seeds in a 10 mL cell plug tray filled with horticultural substrates, and apply fertilizers with less than 500 mg·L^-1 concentration.

• 한국결정성장학회지
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• 제14권4호
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• pp.145-150
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• 2004

We have investigated the structural, electrical and optical properties of Al-doped ZnO (AZO) thin films grown on glass substrate by pulsed DC magnetron sputtering as functions of pulse frequency and substrate temperature. A highly c-axis oriented AZO thin film is grown in perpendicular to the substrate when pulse frequency of 30 kHz and substrate temperature of $400^{\circ}C$ was applied. Under this optimized growth condition, the resistivity of AZO thin films exhibited $7.40\times 10^{-4}\Omega \textrm{cm}$. This indicated that the decrease of film resistivity resulted from the improvement of film crystallinity. The optical transmittance spectra of the films showed a very high transmittance of 85∼90 % in the visible wavelength region and exhibited the absorption edge of about 350 nm. The results show the potential application for transparent conductivity oxide (TCO) thin films.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1378-1383
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• 2003

Synthesis of carbon nanofibers on a metal substrate by an ethylene fueled inverse diffusion flame was illustrated. Stainless steel plates were used for the catalytic metal substrate. The effects of radial distance and residence time of the substrate were investigated. The role of hydrocarbon composition in the fuel was also viewed. Nanofibers with a diameter range of 30-70 nm were found on the substrate. The carbon nanofibers were formed and grown in the region from 4 to 5.5 mm from the central axis of a flame outside of the visible flame front in the radial direction. The minimum residence time required for the formation of carbon nanofibers were about 20 seconds, and over 60 seconds were required for the full-scale growth. The characteristic time of the formation of carbon nanofibers was much shorter than that of the substrate temperature growth. In this study, the variation in hydrocarbon composition had no significant effect on the formation and growth of the carbon nanofibers.

• Journal of Magnetics
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• 제21권2호
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• pp.168-172
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• 2016

$BiMnO_3$ has been a promising candidate as a magnetoelectric multiferroic while there have been many controversial reports on its ferroelectricity. The detailed analysis of its film growth, especially the growth of thin film having monoclinic symmetry has not been reported. We studied the effect of miscut angle, the substrate surface, and film thickness on the symmetry of $BiMnO_3$ thin film. A flat $SrTiO_3$ (110) substrate resulted in a thin film with three domains of $BiMnO_3$ and 1 degree miscut in the $SrTiO_3$ (110) substrate resulted in dominant domain preference in the $BiMnO_3$ thin film. The larger miscut resulted in a nearly perfect detwinned $BiMnO_3$ film with a monoclinic phase. This strong power of domain selection due to the step edge of the substrate was efficient even for the thicker film which showed a rather relaxed growth behavior along the $SrTiO_3$ [1-10] direction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1440-1441
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• 2006

In this study, we synthesized CNTs(carbon nanotubes) on the glass substrate by microwave plasma enhanced chemical vapor deposition (MPECVD), Effect of bias voltage on the grown behavior and morphology of CNTs were investigated. Recently, it has been proposed that aligned CNTs can also be achieved by the application of electric bias to the substrate during growth, the first time reported the bias effect such that the nanotube alignment occurred only when a positive bias was applied to the substrate whereas no aligned growth occurred under a negative bias and no tube growth was observed without bias. On the country, several researchers reported some different observations that aligned nanotubes could also be grown under negative substrate biases. This discrepancy as for the effect of positive and negative bias may indicate that the bias effect is not fully understood yet. The glass and Si wafers were first deposited with TiN buffer layer by r.f sputtering method, and then Ni catalyst same method, The thickness of TiN and Ni layer were 200 nm and 60 nm, respectively. The main process parameters include the substrate bias (0 to - 300 V), and deposition pressure (8 to 20 torr).

• 한국재료학회지
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• 제15권11호
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• pp.741-744
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• 2005

Atomic layer deposition (ALD) is a very promising deposition technique for ZnO thin films. However, there have been very few reports on ZnO grown by ALD. Effects of substrate temperature in both ALD and post annealing on the microstructure and PL properties of ZnO thin films were investigated using X-ray diffraction, photoluminescence, and scanning electron microscopy. The temperature window of ALD is found to be between $130-180^{\circ}C$. The growth rate of ZnO thin film increases as the substrate temperature increases in the temperature range except the temperature window. The crystal quality depends most strongly on the substrate temperature among all the growth parameters of ALD. The crystallinity of the film is improved by increasing the growth thine per ALD cycle or doing post-annealing treatment. The grain size of the film tends to increase and the grain shape tends to change from a worm-like longish shape to a round one as the annealing temperature increases from $600^{\circ}C\;to\;1,000^{\circ}C$.