• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.10
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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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• 2000.07a
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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.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.19-37
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• 1996

Scanning electron microscopy (SEM) has been applied to observe directly the {{{{ SQRT { 19} }}}}${\times}${{{{ SQRT { 19} }}}} and (1${\times}$1)HT reconstructions and the transition associated step bunching on the GaAs (111)B surfaces under As pressure. Close to the transition point, {{{{ SQRT { 19} }}}}${\times}${{{{ SQRT { 19} }}}}an d (1${\times}$1)HT reconstructions are observed in dark and bright domains by SEM and determined by micro-probe reflection high-energy electron diffraction (${\mu}$-RHEED). The reconstruction diagram shows hyster-esis. The stepped surface morphology during the reconstruction transition was unstable. Heavy step bunching with rough macrostep edges was observed.

• Journal of Magnetics
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• v.11 no.1
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• pp.1-4
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• 2006

We report on the growth, structural and transport properties of zinc-blende CrAs/GaAs/MnAs/GaAs multilayers on GaAs(001) substrates. Structural analyses using in-situ reflection high-energy electron diffraction and exsitu cross-sectional transmission electron microscopy confirmed the realization of a zinc-blende crystal structure. Room temperature Hall measurements reveal that the as-grown multilayer exhibits p-type conductivity with a very low resistivity of $0.052\;\omega{cm}$, a high carrier concentration of $6.2X10^{19}\;cm^{-3}$ and a Hall mobility of $1.8\;cm^2/Vs$. We also observed a clear decrease of the resistivity in samples after low temperature annealing.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.19.2-19.2
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• 2011

The $(Sr_{0.75},\;La_{0.25})TiO_3$ (SLTO) ultra-thin films with various thicknesses have been grown on Ti-O terminated $SrTiO_3$(100) substrate using Laser-Molecular Beam Epitaxy (Laser MBE). By monitoring the in-situ specular spot intensity oscillation of reflection high energy electron diffraction (RHEED), we controlled the layer-by-layer film growth. The film structure and topography were verified by atomic force microscopy (AFM) and high resolution thin film x-ray diffraction by the synchrotron x-ray radiation. We have also investigated the electronic band structure using x-ray absorption spectroscopy (XAS). The ultra thin SLTO film exhibits thickness driven metal-insulator transition around 8 unit cell thickness when the film thickness progressively reduced to 2 unit cell. The SLTO thin films with an insulating character showed band splitting in Ti $L_3-L_2$ edge XAS spectrum which is attributed to Ti 3d band splitting. This narrow d band splitting could drive the metal-insulator transition along with Anderson Localization. In optical conductivity, we have found the spectral weight transfer from coherent part to incoherent part when the film thickness was reduced. This result indicates the possibility of enhanced electron correlation in ultra thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.122-122
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• 2000

Magnesium oxide is thermodynamically very stable, has a low dielectric constant and a low refractive index, and has been widely used as substrate for growing various thin film materials, particulary oxides of the perovskite structure. There has been a considerable interest in integrating the physical properties of these oxides with semiconductor materials such as GaAs and Si. In this regard, it is considered very important to be able to grow MgO buffer layers epitaxially on the semiconductors. Various oxide films can then be grown on such buffer layers eliminating the need for using MgO single crystal substrates. Vapor phase epitaxy of magnesium oxide has been accomplished on Si(001) substrates in a high vacuum chamber using the single precursor methylmagnesium tert-butoxide in the temperature range 750-80$0^{\circ}C$. For the epitaxy of the MgO films, SiC buffer layers had to be grown on Si(001). The films were characterized by reflection high energy electron diffraction (RHEED) in situ in the growth chamber, and x-ray diffraction (XRD), x-ray pole figure analysis, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS) after the growth.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.326-328
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• 1995

SiC buffer layers were grown on Si(100) substrates by ultra-high-vacuum electron cryclotron resonance plasma (UHV ECR plasma) from $CH_4/H_2$ mixture at 700$^{\circ}C$. The electron densities and temperature were measured by single probe. The axial plasma potentials measured by emissive probe had the double layer structure at positive substrate bias. Piranha cleaning was carried out as ex-situ wet cleaning. Clean and smooth silicon surface were prepared by in-situ hydrogen plasma cleaning at 540$^{\circ}C$. A short exposure to hydrogen plasma transforms the Si surface from 1$\times$1 to 2$\times$1 reconstruction. It was monitored by reflection high energy electron diffraction (RHEED). The defect densities were analysed by the dilute Schimmel etching. The results showed that the substrate bias is important factor in hydrogen plasma cleaning. The low base pressure ($5\times10^{-10}$ torr) restrains the $SiO_2$ growth on silicon surface. The grown layers showed different characteristics at various substrate bias. RHEED and K-ray Photoelectron spectroscopy study showed that grown layer was SiC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.45-48
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• 2003

BiSrCaCuO thin films were fabricated by atomic layer-by-layer deposition using an ion beam sputtering method. 10 wt% and 90 wt% ozone mixed with oxygen were used with 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 $SrBi_2O_4$ by in-situ anneal.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.289-290
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• 2006

We report a study of Zn(S)Se/GaAs heterojunction solar cells grown by molecular beam epitaxy (MBE). Zn(S)Se/GaAs heterostructures prepared under different conditions were characterized in-situ by reflection high-energy electron diffraction (RHEED). Structural and electrical properties were investigated with double crystal X-ray diffraction and current-voltage characteristics, respectively. The fabricated $n-ZnS_{0.07}Se_{0.93}/p-GaAs$ solar cell (SC #2) exhibited open circuit voltage($V_{oc}$) of 0.37 V, short circuit current($I_{sc}$) of $1.7{\times}10^{-2}$ mA, fill factor of 0.62 and conversion efficiency of 7.8 % under 38.5 $mW/cm^2$ illumination.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.485-485
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• 2013

Plasma-assisted molecular beam epitaxy법으로 자가 형성되는 InN 박막을 활용하여 GaN 박막의 결함밀도를 감소시키는 성장 구조 조건에 대하여 연구하였다. Sapphire 기판 위에 저온에서 GaN 핵층을 3 nm 두께로 성장하고, 그 위에 InN 박막을 성장 한 후, 고온에서 GaN을 성장하였다. InN박막의 성장 온도는 $450^{\circ}C$이고, 성장 시간을 30초에서 1분 30초까지 각각 달리 하였다. 실험결과 InN 층이 삽입된 GaN 박막이 상대적으로 고른 표면이 형성되는 과정을 reflection high energy electron diffraction로 관측하였고, atomic force microscope를 측정하여 표면 거칠기의 개선을 확인하였다. InN 성장시간 변화에 따른 결정학적, 광학적 특성 변화를 x-ray diffraction, photoluminescence 이용하여 조사하였고, 본 연구를 통해 InN박막을 활용한 양질의 GaN 박막 성장 가능성을 확인하였다.