• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.212-217
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• 2000

Bi$_2$Sr$_2$CuO$_{x}$(Bi-2201) thin films have been fabricated by atomic layer-by-layer deposition using ion beam sputtering(IBS) process. During the deposition, 14 wt%-ozone/oxygen mixture gas of typical pressure of 5.0$\times$10$^{-5}$ Torr is supplied with ultraviolet light irradiation for oxidation. XRD and RHEED investigations reveal that a buffer layer with compositions different from Bi-2201 is formed at the early deposition stage of less than 10 units cell and then Bi-2201 oriented along the c-axis is grown.n.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.281-283
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• 2001

Bi$_2$Sr$_2$CuO$\_$x/(Bi-2201) thin films were fabricated layer-by-layer deposition using an ion beam sputtering method. 10 wt% and 90 wt% ozone mixed with oxygen were used ultraviolet light irradiation to assist oxidation. At early stages of the atomic layer by layer deposition, two dimensional epitaxial growth which covers the substrate surface would be suppressed by the stress and strain caused by the lattice misfit, then three dimensional growth takes place. Since Cu element is the most difficult to oxidize, only Sr and Bi react with each other predominantly, and forms a buffer layer on the substrate in an amorphous-like structure, which is changed to SrBi$_2$O$_4$ by in-situ anneal.

• Journal of the Korean institute of surface engineering
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• v.28 no.3
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• pp.174-181
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• 1995

Multilayered silicon cantilever beams as interconnection systems for bare chip burn-in socket applications have been designed, fabricated and characterized. Fabrication processes of the beam are employing standard semiconductor processes such as thin film processes and epitaxial layer growth and silicon wet etching techniques. We investigated silicon etch rate in 1-3-10 etchant as functions of doping concentration, surface mechanical stress and crystal defects. The experimental results indicate that silicon etch rate in 1-3-10 etchant is strong functions of doping concentration and crystal defect density rather than surface mechanical stress. We suggested the new fabrication processes of multilayered silicon cantilever beams.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.3
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• pp.14-19
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• 2000

Free-standing GaN single crystal substrates have been obtained by growing thick GaN epitaxial layers on (0001) sapphire substrates using hydride vapor phase epitaxy (HVPE) method. After growing the GaN thick film of 200 ${\mu}{\textrm}{m}$, a free-standing GaN with a size of 10 mm $\times$10 mm were obtained by mechanical polishing process to remove sapphire substrate. Crack-free GaN substrates have been obtained by GaCl pre-treatment prior to the growth of GaN epitaxial layers. Properties of free-standing GaN substrates have been compared with those of lateral epitaxial overgrowth (LEO) GaN films by double-crystal x-ray diffraction (DC-XRD), cathodoluminescence (CL) and photoluminescence (PL) measurements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.397-398
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• 2005

Ferroelectric Lithium niobate ($LiNbO_3$) thin films are fabricated on $Al_2O_3$(0001) substrate using Pulsed Laser Deposition (PLD). The various deposition conditions such as substrate temperature, oxygen pressure, and post annealing condition are investigated to deposite c-axis oriented $LiNbO_3$ thin films. Highly c-axis oriented thin films are obtained under the conditions of working pressure of 100 mTorr, deposition for 10 min at $450^{\circ}C$, and in-situ annealing for 40 min. The $LiNbO_3$ thin films are chemically etched after electric poling and the etched configurations are studied by scanning electron microscope (SEM).

• Progress in Superconductivity
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• v.13 no.2
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• pp.127-132
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• 2011

Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.370.1-370.1
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• 2014

Giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and magnetic random-access memory (MRAM) are currently active areas of research. Magnetite, Fe3O4, is predicted to possess as half-metallic nature, ~100% spin polarization (P), and has a high Curie temperature (TC~850 K). On the other hand, Spinel ferrite CoFe2O4 has been widely studies for various applications such as magnetorestrictive sensors, microwave devices, biomolecular drug delivery, and electronic devices, due to its large magnetocrystalline anisotropy, chemical stability, and unique nonlinear spin-wave properties. Here we have investigated the magneto-transport properties of epitaxial CoxFe3-xO4 thin films. The epitaxial CoxFe3-xO4 (x=0; 0.4; 0.6; 1) thin films were successfully grown on MgO (100) substrate by molecular beam epitaxy (MBE). The quality of the films during growth was monitored by reflection high electron energy diffraction (RHEED). From temperature dependent resistivity measurement, we observed that the Werwey transition (1st order metal-insulator transition) temperature increased with increasing x and the resistivity of film also increased with the increasing x up to $1.6{\Omega}-cm$ for x=1. The magnetoresistance (MR) was measured with magnetic field applied perpendicular to film. A negative transverse MR was disappeared with x=0.6 and 1. Anomalous Hall data will be discussed.

• 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 Korean Magnestics Society Conference
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• 2009.12a
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• pp.203-203
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• 2009

We report on the epitaxial growth of tetragonal $DO_{22}$-type Mn3Ga films on GaSb (001) using molecular beam epitaxy and the related structural and magnetic properties. The as-studied $Mn_3Ga$ film was found to exhibit relatively small coercivity around 400 Oe, which differs greatly from the hard magnetic properties of $Mn_3Ga$ bulk specimen or films that are normally reported. This difference was probably attributed to the effects of the GaSb (001) substrate that forced the $Mn_3Ga$ film to be two-dimensionlly stabilized in the (114) orientation and thus led to the modified intrinsic properties of $Mn_3Ga$ films. The growth orientation of the Mn3Ga (114)//GaSb (001) also caused the easy magnetocrystalline direction located in the film plane due to the dominant shape anisotropy in the thin films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.343-346
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• 2010

We have investigated growth of CdTe thin films by using (As, GaAs) buffer layers for application of large scale IR focal plane arrays(IFPAs). Buffer layers were grown by molecular beam epitaxy(MBE), which reduced the lattice mismatch of CdTe/Si and prevented native oxide on Si substrates. CdTe thin films were grown by metal organic chemical deposition system(MOCVD). As a result, polycrystalline CdTe films were grown on Si(100) and arsenic coated-Si(100) substrate. In other case, single crystalline CdTe(400) thin film was grown on GaAs coated-Si(100) substrate. Moreover, we observed hillock structure and mirror like surface on the (400) orientated epitaxial CdTe thin film.