• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.368-368
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• 2010

Monolayers of graphite can be grown by fine controlled surface graphitization on the surfaces of various metallic and semiconducting materials. Epitaxial graphene grown on polished silicon carbide crystal surfaces has drawn much attention due to well known vacuum annealing procedures from surface analysis methods, especially scanning tunneling microscopy(STM) and scanning tunneling spectroscopy(STS). In this study, we have grown single layer and few layer graphene on silicon terminated 6H-SiC(0001) crystals. The growth of graphene layers were observed by low energy electron diffraction(LEED) patterns. Scanning tunneling microscopy and spectroscopy measurements were performed to illustrate the electronic structure which may display some clue on the influence of the underlying structure. Spatially resolved STS results acquired at the edges of epitaxial graphene show in detail the electron density of states, which is compared to theoretical calculations. STM measurements were also done on graphene films grown by chemical vapor deposition(CVD) and transferred onto a SiC(0001) crystal. These observations may provide a hint for the understanding of carrier scattering at the edges.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.159-164
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• 2009

We fabricated 40 nm-thick cobalt silicide ($CoSi_2$) as a buffer layer, on p-type Si(100) and Si(111) substrates to investigate the possibility of GaN epitaxial growth on $CoSi_2$/Si substrates. We deposited GaN using a HVPE (hydride vapor phase epitaxy) with two processes of process I ($850^{\circ}C$-12 minutes + $1080^{\circ}C$-30 minutes) and process II ($557^{\circ}C$-5 minutes + $900^{\circ}C$-5 minutes) on $CoSi_2$/Si substrates. An optical microscopy, FE-SEM, AFM, and HR-XRD (high resolution X-ray diffractometer) were employed to determine the GaN epitaxy. In case of process I, it showed no GaN epitaxial growth. However, in process II, it showed that GaN epitaxial growth occurred. Especially, in process II, GaN layer showed selfaligned substrate separation from silicon substrate. Through XRD ${\omega}$-scan of GaN <0002> direction, we confirmed that the combination of cobalt silicide and Si(100) as a buffer and HVPE at low temperature (process II) was helpful for GaN epitaxy growth.

• Journal of the Semiconductor & Display Technology
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• v.6 no.4
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• pp.65-68
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• 2007

An epitaxial NiSi structure on Si (001) substrate was studied by using density functional theory (DFT). Orhorhombic and B2-NiSi structures were compared first. B2 structure was further considered as it has same crystal structure as Si and the lattice mismatch between B2 and Si is small, compared to orthorhombic-NiSi. The lattice parameters of x- and y-direction in B2-NiSi structure were modified to match with those in Si (001). The size reduction of the lattice parameter of B2-NiSi to match with that of Si increased the lattice parameter of z-direction by 10.5%. Therefore, we propose that an optimum structure of NiSi for epitaxial growth on Si (001) is a tetragonal structure.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.93-98
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• 2002

The effect of bonding misfit on single crystallization of transient liquid phase (TLP) bonded joints of single crystal superalloy CMSX-2 was investigated using MBF-80 insert metal. The bonding misfit was defined by (100) twist angle (rotating angle) at bonded interface. TLP bonding of specimens was carried out at 1523K for 1.8ks in vacuum. The post-bond heat treatment consisted of the solution and sequential two step aging treatment was conducted in the Ar atmosphere. The crystallographic orientation analysis across the TLP bonded joints was conducted three dimensionally using the electron back scattering pattern (EBSP) method. EBSP analyses f3r the bonded and post bonded heat treated specimens were conducted. All bonded joints had misorientation centering around the bonded interface for as-bonded and post-bond heat treated specimens with rotating angle. The average misorientation angle between both solid phases in bonded interlayer was almost identical to the rotating angle at bonded interface. HRTEM observation revealed that the atom arrangement of both solid phases in bonded interlayer was quite different across the bonded interface. It followed that grain boundary was formed in bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during TLP bonding and single crystallization could not be achieved in joints with rotating angle.

• Particle and aerosol research
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• v.6 no.1
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• pp.21-27
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• 2010

New process consisting of electrospray and epitaxial crystal growth processes was applied to the preparation of c-plane oriented barium ferrite ($BaFe_{12}O_{19}$) thin film for high density magnetic recording media. Sodium citrate aided process was proper to preparation of amorphous $BaFe_{12}O_{19}$ nanoparticles with geometric mean diameter of 3 nm and geometric standard deviation of 1.1. The electrospray was applicable to the prepare of amorphous $BaFe_{12}O_{19}$ thin film on a substrate, and the film thickness could be controlled by adjusting the electrospray deposition time. The c-plane oriented $BaFe_{12}O_{19}$ thin film was successfully prepared by 3 step annealing process of the $BaFe_{12}O_{19}$ amorphous film on a sapphire($Al_2O_3$) substrate; annealing at $350^{\circ}C$ for 30 min, annealing at $500^{\circ}C$ for 30 min, and annealing at $700^{\circ}C$ for 60 min.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.71-74
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• 1998

$Er^{3+}$ doped $NdF_{3}$ single crystalline thin films with smooth, microcrack-free, and high-crystalline quality were grown on $CaF_{2}(111)$ substrate at $500^{\circ}C$by molecular beem epitaxy(MBE). The relation-ship between subcell and supercell showing the reconstructed $3^{1/2} \times 3^{1/2}$ structure was studied by reflection high-energy electron diffraction(RHEED) investigation. The film surface and the growth mode were examined in studied by RHEED patterns and atomic force microscope(AFM) images ex situ. The crystallinity of film and the lattice mismatch between $NdF_{3}Er}^{3+}(0002)$ film and $CaF_{2}(111)$ substrate depending in the $Er^{3+}$ concentration were investigated by X-ray rocking curve analysis.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.3-26
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• 1999

We have successfully grown <111>-oriented (La,Sr)(Al,Ta)$O_3$(LSAT) mixed-perovskite single crystals and <0001>-oriented $Ca_8La_2(PO_4)_6O_2$(CLPA) single crystals with the apatite structure by the Czochralski method. The compositional and lattice parameter uniformity of the crystals are discussed in relation to the growth conditions. Since LSAT and CLPA single crystals have excellent lattice matching with GaN, they ar promising as new substrates for the growth of high quality GaN epitaxial layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.463-465
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• 2002

In order to increase perpendicular magnetic anisotropy of magnetic layer and prepare magnetic recording layer with a good quality by epitaxial growth between magnetic layer and, we prepared Co$\_$77/Cr$\_$20/Ta$_3$/Si doublelayer for perpendicular magnetic recording media which was promoted as next generation recording media on slide glass substrate. The thickness of magnetic layer and Underlayer were varied from 20 to 100 nm and 5 to 100 m, respectively. The surface morphology and crystal structure of the CoCrTa/Si film were examined with XRD and AFM. Prepared thin films showed improvement of dispersion angle of c-axis orientation Δ$\theta$$\_$50/ caused by inserting amorphous Si underlayer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.271-275
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• 1997

We have successfully grown Cl-doped ZnSe epitaxial layers on GaAs(100) sub-strates by HWE using $ZnCl_2$ as a doping source. The Cl-doped ZnSe layers showed mirrorlike morphology and good crystallinity. It has been found that the layer exhibited an n-type conduction with low resistivity. The carrier concentration is, obtained about $10^{16}\textrm {cm}^{-3}$, where a resistivity reached 10 $\Omega \textrm {cm}$. The layer with an appropriate doping level exhibited blue photoluminescence at room temperature. The strong blue PL was obtained at the hall mobility of $100^2\textrm {cm}$/Vㆍsec.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.3
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• pp.157-160
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• 2002

The ferroelectric domain variation and electrical performance of $Pb(Zr,Ti)O_{3}$ (PZT) based capacitors through La additions were systematically studied. La substitution up to 10 % was performed to lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a (Ti_{0.9}Al_{0.1})N/Pt$ conducting barrier composite. Ferroelectric capacitors substituted with 10 % La show significantly lower coercive voltage compared to capacitors with 0 % and 3 % La. This is attributed to a systematic microstructure change into $180^{\circ}C$ domain and decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. These capacitors show promise as storage elements in low power memory architectures.