• 한국진공학회지
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• 제19권5호
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• pp.371-376
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• 2010

분자선 에피택시 장비를 이용하여 두 단계 방법(two-step method)으로 Si (100) 기판 위에 GaAs 에피층을 성장하였다. Si 기판은 초고진공을 유지하고 있는 MBE 성장 챔버 속에서 세척 방법을 달리하여 Si 기판표면에 존재하는 불순물(산소, 탄소 등)을 제거하였다. 첫 번째는 Si 기판을 몰리브덴 히터를 사용하여 $800^{\circ}C$로 직접 가열하였다. 두 번째는 Si 기판 표면에 As 빔을 조사시켜 주면서 $800^{\circ}C$로 Si 기판을 가열하였다. 세 번째는 Si 기판 표면에 Ga을 증착한 후 Si 기판을 $800^{\circ}C$로 가열하였다. 이와 같은 세 가지 다른 조건으로 세척한 Si(100) 기판 위에 성장한 GaAs 에피층의 특성은 reflection high-energy electron diffraction (RHEED), atomic force microscope (AFM), double crystal x-ray diffraction (DXRD), photoluminescence (PL), photoreflectance(PR) 등으로 조사하였다. Ga 빔을 증착하여 세척한 Si 기판 위에 성장된 GaAs 에피층의 RHEED 패턴은 ($2{\times}4$) 구조를 가지고 있었다. Ga 빔을 증착하여 세척한 Si 기판 위에 성장된 GaAs 에피층이 가장 좋은 결정성을 가지고 있었다.

• 센서학회지
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• 제16권2호
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• pp.85-90
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• 2007

This paper presents the growth conditions and characteristics of polycrystalline 3C-SiC (silicon carbide) thin films for M/NEMS applications related to harsh environments. The growth of the 3C-SiC thin film on the oxided Si wafers was carried out by APCVD using HMDS (hexamethyildisilane: $Si_{2}(CH_{3})_{6})$ precursor. Each samples were analyzed by XRD (X-ray diffraction), FT-IR (fourier transformation infrared spectroscopy), RHEED (reflection high energy electron diffraction), GDS (glow discharge spectrometer), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and TEM (tunneling electro microscope). Moreover, the electrical properties of the grown 3C-SiC thin film were evaluated by Hall effect. From these results, the grown 3C-SiC thin film is very good crystalline quality, surface like mirror and low defect. Therefore, the 3C-SiC thin film is suitable for extreme environment, Bio and RF M/NEMS applications in conjunction with Si fabrication technology.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.533-537
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• 2007

This paper describes the heteroepitaxial growth of single-crystalline 3C-SiC (cubic silicon carbide) thin films on Si (100) wafers by atmospheric pressure chemical vapor deposition (APCVD) at 1350 oC for micro/nanoelectromechanical system (M/NEMS) applications, in which hexamethyldisilane (HMDS, Si2(CH3)6) was used as a safe organosilane single-source precursor. The HMDS flow rate was 0.5 sccm and the H2 carrier gas flow rate was 2.5 slm. The HMDS flow rate was important in obtaing a mirror-like crystalline surface. The growth rate of the 3C-SiC film in this work was 4.3 μm/h. A 3C-SiC epitaxial film grown on the Si (100) substrate was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman scattering, respectively. These results show that the main chemical components of the grown film were single-crystalline 3C-SiC layers. The 3C-SiC film had a very good crystal quality without twins, defects or dislocations, and a very low residual stress.

• 한국재료학회지
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• 제21권10호
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• pp.563-567
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• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
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• pp.501-504
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• 2004

High quality GaN layer was obtained on 0001 sapphire substrate using ammonia($NH_3$) as a nitrogen source by gas source molecular beam epitaxy. As a result, RHEED is used to investigate the relaxation processes which take place during the growth of GaN. In-situ RHEED(reflection high electron energy diffraction) appeared streaky-like pattern. The full Width at half maximum of the x-ray diffraction(FWHM) rocking curve measured from plane of GaN has exhibited as narrow as 8arcmin and surface roughness was 7.83nm. Photoluminescence measurement of GaN was investigated at room temperature, where the intensity of the band edge emission is much stronger than that of deep level emission. The GaN epitaxy layer according to various growth condition was investigated.

• Applied Science and Convergence Technology
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• 제26권3호
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• pp.52-54
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• 2017

An InGaN/GaN multiple quantum well (MQW) structure is grown on a GaN/sapphire template using a plasma-assisted molecular beam epitaxy (PA-MBE). The fluctuation of the quantum well thickness formed from roughly-grown InGaN layer results in a disordered photoluminescence (PL) spectrum. The surface morphologies of the InGaN layers with various In compositions are investigated by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). A blurred InGaN/GaN hetero-interface and the non-uniform QW size is confirmed by high resolution transmission electron microscopy (HR-TEM). Inhomogeneity of the quantum confinement results in a degradation of the quantum efficiency even though the InGaN layer has a uniform In composition.

• 한국표면공학회지
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• 제43권4호
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• pp.176-179
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• 2010

The InAs thin films were grown on GaAs(100) substrate with $2^{\circ}C$ tilted toward [$0\bar{1}\bar{1}$] with different As beam equivalent pressure (BEP) by using molecular beam epitaxy. Growth temperature and thickness of the InAs thin films were $480^{\circ}C$ and 0.5 ${\mu}m$, respectively. We studied the relation between the As BEP and the properties of InAs thin films. The properties of InAs thin films were observed by reflection high-energy electron diffraction (RHEED), optical microscope, and Hall effect. The growth, monitored by RHEED, was produced through an initial 2D (2-dimensional) nucleation mode which was followed by a period of 3D (3-dimensional) island growth mode. Then, the 2D growth recovered after a few minutes and the streak RHEED pattern remained clear till the end of growth. The crystal quality of InAs thin films is dependent strongly on the As BEP. When the As BEP is $3.6{\times}10^{-6}$ Torr, the InAs thin film has a high electron mobility of 10,952 $cm^2/Vs$ at room temperature.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.318.2-318.2
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• 2016

FeM2X4 spinel structures, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. Both the Fe and M ions can occupy tetrahedral and octahedral sites; therefore, these types of compounds can display various physical and chemical properties [1]. On the other hand, the electronic and magnetic properties of these spinel structures could be modified via the control of cation distribution [2, 3]. Among the spinel oxides, iron manganese oxide is one of promising materials for applications. FeMn2O4 shows inverse spinel structure above 390 K and ferrimagnetic properties below the temperature [4]. In this work, we report on the structural and magnetic properties of epitaxial FeMn2O4 thin film on MgO(100) substrate. The reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) results indicated that films were epitaxially grown on MgO(100) without the impurity phases. The valance states of Fe and Mn in the FeMn2O4 film were carried out using x-ray photoelectron spectrometer (XPS). The magnetic properties were measured by vibrating sample magnetometer (VSM), indicating that the samples are ferromagnetic at room temperature. The structural detail and origin of magnetic ordering in FeMn2O4 will be discussed.

• 한국결정성장학회지
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• 제13권1호
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• pp.19-23
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• 2003

Polished surface of $CsB_{3}O_{5}$ (CBO) has been observed by reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS). For comparison, electronic properties of CBO powder have been studied by XPS. It has been found that the crystal surface is covered by thick amorphous layer with chemical composition closely related to that of CBO. Great enrichment of top surface by cesium, ~30 % in reference to the bulk of the modified layer, has been displayed by depth profiling.