• Journal of the Optical Society of Korea
• /
• 제16권1호
• /
• pp.53-56
• /
• 2012

We have developed a slab-type Nd:YAG gain module based on the techniques of conduction cooling and end pumping. The Nd:YAG slab is end-capped on both ends by undoped pure YAG and is pumped through the end-caps by stacked arrays of laser diode bars. The slab's surfaces of total internal reflection are in contact on both sides with microchannel cooling blocks which are cooled by water circulation. The power oscillator based on the gain module generates more than 400 W at 1-kW pumping with a slope efficiency of 55%. The small-signal gain of the gain module is 10 in a single zig-zag pass, and the amplified beam shows a near diffraction-limited beam quality.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.7-7
• /
• 2011

Quantum beam technology has been expected to develop breakthroughs for nanotechnology during the third basic plan of science and technology (2006~2010). Recently, Green- or Life Innovations has taken over the national interests in the fourth basic science and technology plan (2011~2015). The NIMS (National Institute for Materials Science) has been conducting the corresponding mid-term research plans, as well as other national projects, such as nano-Green project (Global Research for Environment and Energy based on Nanomaterials science). In this lecture, the research trends in Japan and NIMS are firstly reviewed, and the typical achievements are highlighted over key nanotechnology fields. As one of the key nanotechnologies, the quantum beam research in NIMS focused on synchrotron radiation, neutron beams and ion/atom beams, having complementary attributes. The facilities used are SPring-8, nuclear reactor JRR-3, pulsed neutron source J-PARC and ion-laser-combined beams as well as excited atomic beams. Materials studied are typically fuel cell materials, superconducting/magnetic/multi-ferroic materials, quasicrystals, thermoelectric materials, precipitation-hardened steels, nanoparticle-dispersed materials. Here, we introduce a few topics of neutron scattering and ion beam nanofabrication. For neutron powder diffraction, the NIMS has developed multi-purpose pattern fitting software, post RIETAN2000. An ionic conductor, doped Pr2NiO4, which is a candidate for fuel-cell material, was analyzed by neutron powder diffraction with the software developed. The nuclear-density distribution derived revealed the two-dimensional network of the diffusion paths of oxygen ions at high temperatures. Using the high sensitivity of neutron beams for light elements, hydrogen states in a precipitation-strengthened steel were successfully evaluated. The small-angle neutron scattering (SANS) demonstrated the sensitive detection of hydrogen atoms trapped at the interfaces of nano-sized NbC. This result provides evidence for hydrogen embrittlement due to trapped hydrogen at precipitates. The ion beam technology can give novel functionality on a nano-scale and is targeting applications in plasmonics, ultra-fast optical communications, high-density recording and bio-patterning. The technologies developed are an ion-and-laser combined irradiation method for spatial control of nanoparticles, and a nano-masked ion irradiation method for patterning. Furthermore, we succeeded in implanting a wide-area nanopattern using nano-masks of anodic porous alumina. The patterning of ion implantation will be further applied for controlling protein adhesivity of biopolymers. It has thus been demonstrated that the quantum beam-based nanotechnology will lead the innovations both for nano-characterization and nano-fabrication.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
• /
• pp.289.1-289.1
• /
• 2007

• 한국전기전자재료학회논문지
• /
• 제13권6호
• /
• pp.467-471
• /
• 2000

The thermal annealing effect of $Zn_{0.9}Cd_{0.1}$ single quantum-well structures grown by molecular beam epitaxy is investigated. As the results of before and after rapid thermal annealed samples a red shift of E1-HH1 peak by Cd interdiffusion during thermal annealing of ZnCeSe/ZnSe sample was observed. In the case of annealed sample over $450^{\circ}C$ donor and acceptor impurities related peaks were observed which seems to be due to a diffusion of Ga and As from GaAs substrate. And also interdiffusion phenomena is idenified by the results of DCX measurements and which are consisten with the PL measurements.

• 한국초전도ㆍ저온공학회논문지
• /
• 제21권2호
• /
• pp.1-9
• /
• 2019

Practical superconducting wires are designed with a composite structure to meet the desired engineering characteristics by expert selection of materials and design of the architecture. In practice, the local strain exerted on the superconducting component influences the electromagnetic properties. Here, recent progress in methods used to measure the local strain in practical superconducting wires and conductors using quantum beam techniques is introduced. Recent topics on the strain dependence of critical current are reviewed for three major practical wires: $Nb_3Sn$, BSCCO-2223 and REBCO tapes.

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

• 한국진공학회지
• /
• 제19권5호
• /
• pp.365-370
• /
• 2010

분자선 에피택시 방법을 이용하여 GaAs 기판 위에 GaAs 및 AlGaAs 에피층을 성장하면서 성장 멈춤 효과를 연구하였다. 성장 멈춤 시간에 따른 에피층 성장 과정은 반사 고에너지 전자회절로 측정하였다. 성장 멈춤 시간은 0, 15, 30, 60초로 하였다. 그리고 성장 멈춤 시간을 달리하여 GaAs/$Al_{0.3}Ga_{0.7}As$ 다양자우물을 성장한 후 양자우물의 특성을 조사하였다. 반사 고에너지 전자회절의 강도 진동은 성장 멈춤 시간에 영향을 받고 있었다. 그리고 양자우물의 광특성도 성장 멈춤 시간에 의존하고 있었다. 성장 멈춤 시간이 30초일 때 우물과 장벽층 사이에 급준한 계면을 가지는 에피층을 얻을 수 있었다.

• 한국재료학회지
• /
• 제12권3호
• /
• pp.195-199
• /
• 2002

Planar Hall effect of ferromagnetic GaMnAs thin films was investigated for the first time. The films were grown in an optimized growth condition via molecular beam epitaxy at low temperatures. For the optimization of the growth conditions, we used reflection high-energy electron diffraction, electrical conductivity, double crystal x-ray diffraction, and superconducting quantum interference device measurements techniques. We observed that the difference between the longitudinal resistance and the transverse resistance matches the planar Hall resistance. The ratio of the planar Hall resistance at saturation magnetic field to that at zero reached above 500%.

• 반도체디스플레이기술학회지
• /
• 제5권2호
• /
• pp.1-5
• /
• 2006

The GaN thin film on the 8 periods InGaN/GaN multi-quantum well structure was grown on the sapphire substrate using metal-organic chemical vapor deposition. The nano-scaled triangular-lattice holes with the diameter of 150 nm were patterned on a polymethylmethacrylate blocking film using an electron beam nano-lithography system. The thin slab and two-dimensional photonic crystals with the thickness of 28 nm were fabricated on the GaN layer for the blue light diffraction sources. The photonic crystal with the lattice parameter of 460 nm enhances spectral intensity of photoluminescence indicating that the photonic crystals provides the source of nano-diffraction for the blue light of the 450-nm wavelength.

• 전자공학회논문지A
• /
• 제32A권12호
• /
• pp.142-148
• /
• 1995

Sb ${\delta}$-doped Si layers were grown by Si MBE (Molecular Beam Epitaxy) system using substrate temperature modulation technique. The Si substrate temperatures were modulated between 350$^{\circ}C$ and 600$^{\circ}C$. The doping profile was as narrow as 41$\AA$ and the doping concentration of up to 3.5${\times}10^{20}cm^{3}$ was obtained. The film quality was as good as bulk material as verified by RHEED (Reflected High Energy Electron Diffraction), SRP (Spreading Resistance Profiling) and Hall measurement. Since the film quality is not degraded after the growth a Sb ${\delta}$-doped Si layer, the ${\delta}$-doped layers can be repeated as many times as we want. The doping technique is useful for many Si devices including small scale devices and those which utilize quantum mechanical effects.