• Korean Journal of Materials Research
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• 제28권5호
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• pp.279-285
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• 2018

Graphene is an interesting material because it has remarkable properties, such as high intrinsic carrier mobility, good thermal conductivity, large specific surface area, high transparency, and high Young's modulus values. It is produced by mechanical and chemical exfoliation, chemical vapor deposition (CVD), and epitaxial growth. In particular, large-area and uniform single- and few-layer growth of graphene is possible using transition metals via a thermal CVD process. In this study, we utilize polystyrene and boron oxide, which are a carbon precursor and a doping source, respectively, for synthesis of pristine graphene and boron doped graphene. We confirm the graphene grown by the polystyrene and the boron oxide by the optical microscope and the Raman spectra. Raman spectra of boron doped graphene is shifted to the right compared with pristine graphene and the crystal quality of boron doped graphene is recovered when the synthesis time is 15 min. Sheet resistance decreases from approximately $2000{\Omega}/sq$ to $300{\Omega}/sq$ with an increasing synthesis time for the boron doped graphene.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제13권10호
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• pp.828-833
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• 2000

Growth characteristics and microstructure of AIN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the micorstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.111-114
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• 2000

Growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• Journal of the Korean Vacuum Society
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• 제1권1호
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• pp.67-72
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• 1992

The growth of Ti on Si(111)-$7{\times}7$ and the formation of epitaxial C54 $TiSi_2$ were investigated by using reflection high energy electron diffraction(RHEED) and high resolution transmission electron microscopy(HRTEM). Polycrystalline Ti layer is grown on the amorphous Ti-Si interlayer which is formed at the Ti/Si interface by Ti deposition on Si(111)-$7{\times}7$ at room temperature (RT). HRTEM lattice image and transmission electron diffraction(TED) showed that epitaxial C54 $TiSi_2$ grown on Si substrate with 160 ML of Ti on Si(111)-$7{\times}7$ surface at RT, followed by annealing at $750^{\circ}C$ for 10 min in UHV. Thin single crystal Si overlayer with [111] direction is grown on $TiSi_2$ surface when $TiSi_2$/Si(111) is annealed at ${\sim}900^{\circ}C$ in UHV, which was confirmed by Si(111)-$7{\times}7$ superstructure.

• Journal of the Microelectronics and Packaging Society
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• 제26권4호
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• pp.113-118
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• 2019

In this study, we investigated the growth of single-crystallinity α-Ga₂O₃ thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga₂O₃. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510℃, and the α-Ga₂O₃ thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 ㎛, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 10⁴ cm^-2.

• Journal of the Korean Vacuum Society
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• 제14권4호
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• pp.222-228
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• 2005

Undoped GaN epitaxial layer was grown on c-plane sapphire substrate by a two-step growth with metalorganic chemical vapor deposition(MOCVD). We have investigated the effects of the variation of final growth temperature on surface morphology, roughness, crystal quality, optical property, and electrical property In a horizontal MOCVD reactor, the film was grown at 300 Tow low-pressure with a fixed nucleation temperature of $500^{\circ}C$, varing the final growth temperature from $850\~1050^{\circ}C$ . The undoped GaN epilayers were characterized by atomic force microscopy, high-resolution x-ray diffractometer, photoluminescence, and Hall effect measurement.

• Journal of the Korean Magnetics Society
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• 제9권5호
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• pp.256-262
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• 1999

Sputter deposited CoCr(Mo)/Si film were studied with emphasis on the correlation between magnetic properties and crystallographic orientation. The perpendicular coercivities of CoCr films decreased with Si underlayer thickness, whereas those of CoCrMo films increased with Si underlayer thickness. It has been explained that additions of the larger atomic radius Mo atoms in CoCr films impedes crystal growth resulting in a decrease in grain size, thus this small grain size may induce high perpendicular coercivity. The c-axis alignment of CoCrMo film was improved due to addition of 2at.%Mo. It means CoCrMo layer grow self-epitaxial directly from orientation and structure of Si underlayer when the main layer grow on underlayer.

• Korean Journal of Materials Research
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• 제4권1호
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• pp.81-89
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• 1994

Ti film of lOnm thickness and Co film of 18nm thickness were sequentially e-heam evaporated onto Si (100) substrates. Metal deposited samples were rapidly thermal-annt.aled(KTA) in thr N1 en vironment a t $900^{\circ}C$ for 20 sec. to induce the reversal of metal bilayer, so that $CoSi_{2}$ thin films could be formed. The sheet resistance measured by the 4-point probe was 3.9 $\Omega /\square$This valur was maintained with increase in annealing time upto 150 seconds, showing high thermal stab~lity. Thc XRII spectra idrn tified the silicide film formed on the Si substrate as a $CoSi_{2}$ epitaxial layer. The SKM microgr;iphs showed smooth surface, and the cross-sectional TKM pictures revealed that the layer formed on the Si substrate were composed of two Co-Ti-Si alloy layers and 70nm thick $CoSi_{2}$ epl-layer. The AES analysis indicated that the native oxide on Si subs~rate was removed by TI ar the beginning of the RTA, and Ihcn that Co diffused to clean surface of Si substrate so that epitaxial $CoSi_{2}$ film could bt, formed. In thc rasp of KTA at $700^{\circ}C$. 20sec. followed by $900^{\circ}C$, 20sec., the thin film showed lower sheet resistance, but rough surface and interface owing to $CoSi_{2}$ crystal growth. The application scheme of this $CoSi_{2}$ epilayer to VLSI devices and the thermodynarnic/kinetic mechan~sms of the $CoSi_{2}$ epi-layer formation through the reversal of Co/Ti bdayer were discussed.

• Korean Journal of Crystallography
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• 제1권1호
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• pp.19-28
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• 1990

6H-SiC is a promising material (Eg=3.0eV) for blue light-emitting doide and high-temperature semiconducting device. In the experiment, single crystals of a-SiC have been grown by the sublimation method to fabricate blue light~emitting diode. During the growth of a-SiC single crystals, a temperature Vadient, yonh temperature and pressure ranges were kept 44℃/cm , 1800-1990℃ and 50-1000 mTorr, respectively. Single crystals obtained in Acheson furnace were used as seed crystals. Polarizing microscopy and back-reflection X-ray Laue diffraction showed that the a-SiC crystal was epitaxially and on the seed crytal. It was found by XRD analysis that when other growth conditions were the same, a-SiC was grown at the temperature above 1840℃ and 3C-SiC was gown at lower temperature or under low supersaturation of vapor. The carrier type. concentration and mobility were measured be hole(p-type), 7.6x1014cm-3 and 19cm2V-1sec-1, respectively, by van der Pauw method.

• Korean Journal of Crystallography
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• 제1권2호
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• pp.99-104
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• 1990

The hetero-epitaxial growth of AmB v type onto-electronic material is attempted by means of the laser-induced chemical vapour deposition technique. The bimolecular gas phase reaction of trimethylgallium with ammonia on (001) alumina substrate for the epitaxy of gallium nitride is chosen as a model system. In this study, ArF exciter laser (193nm) is employed as a photon source. Marked difference is found in nucleation and in subsequent crystal incorporation between the doposits formed with and without the laser-irradiation. The surface coverage with isomorphically grown drystallites is pronounced upon "volume-excited" irradiation in comparison with the conventional thermal process. As to the crystal structure of the grown layers, the laser-induced deposits of GaN may be represented by either of the following two models: (001) plane of sapphire //y (001) plane of wurtzite-type GaN, OR (001) plane of sapphire//(001) plane of wurtzite-type-GaN (111) plane of twinned zinc blende-type GaN.