• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.210.1-210.1
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• 2014

The hexagonal boron nitride (h-BN) sheet, a 2D material like graphene sheet, is comprised of boron and nitrogen atoms. Similar to graphene, h-BN sheet has attractive mechanical properties while it has a wide band gap unlike graphene. Recently, many experimental groups studied the growth of single BN layer by chemical vapor deposition (CVD) method on the copper substrate. To study the initial stage of h-BN growth on the copper surface, we have performed density functional theory calculations. We investigate several adsorption sites of a boron or nitride atom on the Cu surfaces. Then, by increasing the number of adsorbed B and N atoms, we study formation behaviors of the BN flakes on the surface. Several types of BN flakes atoms such as triangular, linear, and hexagonal shapes are considered on the copper surface. We find that the formation of the BN flake in triangular shape is most favorable on the surface. On the basis of the theoretical results, we discuss the growth mechanism of h-BN layer on the copper surfaces in terms of its shapes in the initial stage of growth.

• Tribology and Lubricants
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• v.38 no.6
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• pp.235-240
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• 2022

Atomically-thin 2D nanomaterials can be easily deformed and have surface corrugations which can influence the frictional characteristics of the 2D nanomaterials. Chemical vapor deposition (CVD) graphene can be grown in a wafer scale, which is suitable as a large-area surface coating film. The CVD growth involves cooling process to room temperature, and the thermal expansion coefficients mismatch between graphene and the metallic substrate induces a compressive strain in graphene, resulting in the surface corrugations such as wrinkles and atomic ripples. Such corrugations can induce the friction anisotropy of graphene, and therefore, accurate imaging of the surface corrugation is significant for better understanding about the friction anisotropy of CVD graphene. In this work, the combinatorial analysis using friction force microscopy (FFM) and transverse shear microscopy (TSM) was implemented to unveil the friction anisotropy of CVD bi-layer graphene. The periodic friction anisotropy of the wrinkles was measured following a sinusoidal curve depending on the angles between the wrinkles and the scanning tip, and the two domains were observed to have the different friction signals due to the different directions of the atomic ripples, which was confirmed by the high-resolution FFM and TSM imaging. In addition, we revealed that the atomic ripples can be easily suppressed by ironing the surface during AFM scans with an appropriate normal force. This work demonstrates that the friction anisotropy of CVD bilayer graphene is well-correlated with the corrugated structures and the local friction anisotropy induced by the atomic ripples can be controllably removed by simple AFM scans.

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.169-174
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• 2007

TRISO coated fuel particle is one of the most important materials for hydrogen production using HTGR (high temperature gas cooled reactors). It is composed of three isotropic layers: inner pyrolytic carbon (IPyC), silicon carbide (SiC), outer pyrolytic carbon (OPyC) layers. In this study, TRISO coated fuel particle layers were deposited through CVD process in a horizontal hot wall deposition system. Also the computational simulations of input gas velocity, temperature profile and pressure in the reaction chamber were conducted with varying process variable (i.e temperature and input gas ratios). As deposition temperature increased, microstructure, chemical composition and growth behavior changed and deposition rate increased. The simulation showed that the change of reactant states affected growth rate at each position of the susceptor. The experimental results showed a close correlation with the simulation results.

• Journal of the Korea Computer Industry Society
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• v.8 no.1
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• pp.17-22
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• 2007

Carbon nanotubes (CNTs) were grown by a thermal chemical vapor deposition (CVD) method, which has been regarded as one of the most promising candidates for the synthesis of CNTs due to low cost and high growth yield. The Ethylene $(C_2H_4)$, hydrogen $(H_2)$ and Argon(Ar) gases were used for the growth of CNTs at $700^{\circ}C$. As a catalyst for CNTs growth, Fe thin film and Iron nitrate and Molybdenyl acetylacetonate solution with alumina nano-particle were prepared on $SiO_2/Si$ substrate. The growth properties of CNTs were analyzed by SEM and AFM.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.3
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• pp.273-278
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• 2014

On poly and single crystalline Cu substrates, the graphene was synthesized by chemical vapor deposition(CVD). Optical microscopic images which were not possible to show the detailed characterization of graphene growth were adjusted and analyzed using image analyzing software. As a result it was possible to show the detailed growth mechanism of graphene by utilizing the image analysis. Nucleation of graphene on Cu grain boundary and its growth behavior into Cu grain are shown. In addition, the movement of graphene grain boundary interacting with Cu grain boundary and pinholes during growth was illustrated in detail, and the cause and result are discussed as a result of those interactions.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.33-33
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• 1998

Invisible charged clusters are suggested to form in the gas phase and to become the growth unit in the thin film process. Similar suggestion had been made by Glasner el al. in the crystal growth of KBr and KCL in the solution where the lead ions were added. The charged cluster model, which was suggested in the diamond CVD process by our group, will be extended to the other thin film processes. It will be shown based on both the theoretical analysis and the experimental evidences that the charged clusters are formed in the gas phase and become the growth unit of the crystal in the thin film process.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.92-99
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• 2002

This work investigated the optimal condition for an uniform deposition growth rate in the vertical cylindric CVD chamber. Heat transfer, surface chemical reaction and mass diffusion in the flow field of CVD chamber h,id been computed using Fluent v5.3 code. A SIMPLE based finite Volume Method (FVM) was adopted to solve the fully elliptic equations for momentum, temperature and concentration of a chemical species. The numerical analysis results show good agreements with the measurements obtained by N. Yoshikawa. The results obtained by the numerical analysis showed that the film growth rate in the center of a susceptor is increasing, as the inner flow approaches to the forced convection. To the contrast, as it approaches to the natural convection, that in the outside of a susceptor is increasing. As the Reynolds number increases, the uniformity may not hold due to the larger temperature gradient at a susceptor surface. Therefore, when the temperature gradient on the surface of a susceptor is zero, the film growth rate becomes uniform on most surface.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.531-533
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• 1996

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.34-39
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• 1995

Various silicon films were prepared by thermal- and UV photo-CVD processes. The reactants were SiH4, Si2H6, SiH2F2, SIF4, and H2. Silicon films grown at temperatures below $500 ^{\circ}C$ were either amorphous or crystalline depending on the process conditions, and the growth rates ranged between 5 and $80\AA$min. Crystallinity of the film was improved even at $250^{\circ}C$ when the film was grown by photo-CVD using fluoro-silanes as the reactants. Analysis of the film by RBS, SIMS, XRD, and ex-situ IR indicated that substrate surface was contaminated by oxygen and other impurities when the reactants contained neither hydrogen nor fluoro-silnanes, but when fluoro-silanes were used as reactants the silicon film was highly crystalline.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1533-1536
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• 2001

To grow the diamond films by using RF-MW two step process, at first, diamond seeds were deposited on silicon substrate by RF plasma CVD, and then a diamond layer grown by MW plasma CVD on the seeds. The grain-size of diamond films deposited by using RF-MW two step process was smaller and denser and also, crystallity of diamond film was better than those of the MW plasma CVD process. The deposited diamond films were analyzed by SEM(scanning electron microscophy), XRD (x-ray diffraction), and Raman spectroscopy.