This study aimed to grow single crystals with low dislocation density using a heat exchange method using room temperature water, and investigated the effect of the structure of the heat exchanger under the crucible on the defects and dislocation density of the single crystals and the shape of the solid-liquid interface of the crystals, and obtained the following conclusions. The dislocation density of sapphire single crystal grown at 2,200℃ for 30 min and a growth rate of 0.2℃/min was 0.92x103pcs/㎠. Mo guard was used to stabilize the solid-liquid interface grown from seeds, and sapphire single crystals with a diameter of 130㎜ and a height of 75㎜ were grown.

Solid state grain growth (SSCG) is a method of growing large single crystals from seed single crystals by abnormal grain growth in a small-grained matrix. During grain growth, pores are often trapped in the matrix and remain in single crystals. Aerosol deposition (AD) is a method of manufacturing films with almost full density from nano grains by causing high energy collision between substrates and ceramic powders. AD and SSCG are used to grow single crystals with few pores. BaTiO3 films are coated on (100) SrTiO3 seeds by AD. To generate grain growth, BaTiO3 films are heated to 1,300 oC and held for 10 h, and entire films are grown as single crystals. The condition of grain growth driving force is ΔGmax < ΔGc ≤ ΔGseed. On the other hand, the condition of grain growth driving force in BaTiO3 AD films heat-treated at 1,100 and 1,200 oC is ΔGc < ΔGmax, and single crystals are not grown.

Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a BaTiO3 coating layer with ~ 9 μm thickness is fabricated using an aerosol deposition method on (100) and (110) cut SrTiO3 single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and 1,300℃ for 5 h). BaTiO3 layer shows different growth behavior and X-ray diffraction depending on cutting direction of SrTiO3 seed. Rectangular pillars at SrTiO3 (100) and laminating thin plates at SrTiO3 (110), respectively, are observed.

Grain-growth behavior in the 95Na1/2Bi1/2TiO3-5BaTiO3 (mole fraction, NBT-5BT) system has been investigated with the addition of Na2CO3. When Na2CO3 is added to NBT-5BT, the growth rate is higher than desired and grains are already impinging each other during the initial stage of sintering. The grain size decreases as the sintering temperature increases. With the addition of Na2CO3, a liquid phase infiltrates the interfaces between grains during sintering. The interface structure can be changed to be more faceted and the interface migration rate can increase due to fast material transport through the liquid phase. As the sintering temperature increases, the impingement of abnormal grains increases because the number of abnormal grains increases. Therefore, the average grain size of abnormal grains can be decreased as the temperature increases. The phenomenon can provide evidence that grain coarsening in NBT-5BT with addition of Na2CO3 is governed by the growth of facet planes, which would occur via mixed control.

The γ/γ´ two-phases, commonly known as a eutectic structure, are observed in the γ interdendritic region of a Nibase superalloy. However, the growth behavior of the γ/γ´ two-phases, whether it is of eutectic or peritectic nature, has not been decidedly established. Directional solidifications were, thus, performed with the planar interface at a low growth rate of 0.5 μm/s in order to promote macro segregation. Directional solidification started with the γ planar interface and the γ´ phase nucleated on the γ planar interface at the solidification fraction of 0.75. The γ/γ´ two-phases showed the γ´ rod structure as major phase and the γ minor phase between γ´ rods, and the volume fraction of the γ phase changed continuously with an increasing solidification fraction. The two-phase γ/γ´ is seen as the coupled peritectic.

A stoichiometric mixture of evaporating materials for ZnAl2Se4 single-crystal thin films was prepared in a horizontalelectric furnace. These ZnAl2Se4 polycrystals had a defect chalcopyrite structure, and its lattice constants were a0=5.5563Åand c0=10.8897Å.To obtain a single-crystal thin film, mixed ZnAl2Se4 crystal was deposited on the thoroughly etched semi-insulating GaAs(100) substrate by a hot wall epitaxy (HWE) system. The source and the substrate temperatures were 620oCand 400oC, respectively. The crystalline structure of the single-crystal thin film was investigated by using a double crystal X-ray rocking curve and X-ray diffraction ω-2θ scans. The carrier density and mobility of the ZnAl2Se4 single-crystal thin filmwere 8.23×1016cm−3 and 287m2/vs at 293K, respectively. To identify the band gap energy, the optical absorption spectra ofthe ZnAl2Se4 single-crystal thin film was investigated in the temperature region of 10-293K. The temperature dependence ofthe direct optical energy gap is well presented by Varshni's relation: Eg(T)=Eg(0)−(αT2/T+β). The constants of Varshni'sequation had the values of Eg(0)=3.5269eV, α=2.03×10−3eV/K and β=501.9K for the ZnAl2Se4 single-crystal thin film.The crystal field and the spin-orbit splitting energies for the valence band of the ZnAl2Se4 were estimated to be 109.5meVand 124.6meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicatethat splitting of the ∆so definitely exists in the Γ5 states of the valence band of the ZnAl2Se4/GaAs epilayer. The threephotocurrent peaks observed at 10K are ascribed to the A1-, B1-exciton for n=1 and C21-exciton peaks for n=21.

Single crystal ZnIn2S4 layers were grown on thoroughly etched semi-insulating GaAs(100) substrateat 450oC with hot wall epitaxy (HWE) system by evaporating ZnIn2S4 source at 610oC. The crystalline structureof the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray rockingcurve (DCRC). The temperature dependence of the energy band gap of the ZnIn2S4 obtained from theabsorption spectra was well described by the Varshni’s relation, Eg(T)=2.9514eV-(7.24×10−4eV/K)T2/(T＋489K). After the as-grown ZnIn2S4 single crystal thin films were annealed in Zn-, S-, and In-atmospheres, theorigin of point defects of ZnIn2S4 single crystal thin films has been investigated by the photoluminescence (PL)at 10K. The native defects of VZn, VS, Znint, and Sint obtained by PL measurements were classified as a donorsor acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted ZnIn2S4 singlecrystal thin films to an optical p-type. Also, we confirmed that In in ZnIn2S4/GaAs did not form the nativedefects because In in ZnIn2S4 single crystal thin films existed in the form of stable bonds.

In this study, a vertical type LPE system has been developed for III-V semiconductor compounds single crystal growth. On the basis of the experience & basic study using this system, the system modification has been carried out for a ultra thin multi-layer single crystal. The temperature fluctuation was within ±0.006℃ at 800℃, temperature uniformity for graphite boat around was within ±0.15℃ at 650℃, and cooling rate was controllable from 2.2℃/min to 0.05℃/min. As a result it is considered to satisfy the condition to grow a ultra thin layer single crystal of III-V semiconductor compounds.

Shortening the lasing wavelength(particularly below infrared ; the visible region) of laser diodes is very attractive because it can provide a wide range of applications in the fields of optical information, measurement, sensor, the development of medical instrument, and optical communication through plastic fibers. According to the recent researches on the field, InGaAsP/GaAs was suggested as a material for red-light laser. In this study, in order to grow InGaAsP/GaAs epitaxial layer on InGaAsP/GaAs by LPE, we used GaP and InP two phase solution technique for 670nm and 780 nm region, respectively. Through the X-ray diffraction measurement for the epitaxial layer grown from the experiments, we found that the lattice mismatch of In0.46Ga0.54As0.07P0.93/GaAs and In0.19Ga0.81As0.62P0.38/GaAs was about +0.3% and +0.1%, respectively.