Preferred orientation (PO) of chemical vapor deposited polycrystalline films greatly affects film properties. Therefore controlling PO has provoked a great deal of controversy in many years [ 1,2] . We have found a relation between PO and flux of the growth species and explained it by the rate-determining step of adsorption or reaction by applying Langmuir-type adsorption model.
The In_xGa_<1-x> As layers were grown on composition converted InAs(111)B patterned substrates by liquid phase epitaxy. Grown layer with flat and mirror-like surface was obtained. Ga compositions of the depth direction on InAs substrates was decreasing. Ga and In compositions of the In_xGa_<1-x>(x=0.8) layers were found to be uniform.
We analyze the stabilization mechanism in the DAS structure formation on Si(111). A single faulted (F) half of the unit cell of the DAS structure grows into a small DAS domain. Atomic-structure modeling of the formation process of a new F-half implies that a corner-hole shared by two F-halves reduces the number of dangling bonds. We calculated the surface free energy during the 7×7 DAS domain growth. The critical size is in good agreement with our experimental results.
Tetra-n-Butyl Ammonium Bromide (TBAB: (C_4H_9)_4N・Br) forms a semiclathrate-hydrate crystal with water molecules under atmospheric pressure. We carried out in situ observation of this crystal to investigate the growth mechanism of hydrate crystals. The morphology of growing crystal depends on the supercooling. The growth velocity of bottom plane was a function of supercooling. On the other hand, the side plane did not grow under the supercooling 1.4 K. We concluded that the growth of TBAB semiclathrate-hydrate crystals is extremely prohibited by intertacial kinetics.
In-situ observations of CO_2 hydrate and N_2 hydrate growth using a high-energy X-rays were done at high-pressures, and growth rates of each hydrate from ice particles were measured. Assuming a model of diffusion in the hydrate layers, mass-diffusion coefficients of guest molecules and H_2O molecules were calculated.
We in-situ observed the interfaces between ice and water including AFGP using one-directional growth method to clarify a change of the growth kinetics. As a result, it was found that the position of the prismatic interface periodically changed and that of basal interface was constant. We will discuss about the mechanism of this oscillatory growth.
We propose a new method of fringe analysis, in which we shift a phase of interferogram to π/4 and π/2 on Fourier space, compute its inverse Fourier transform and obtain two phase shift images from the original. We applied the method to actual image and exactly reconstructed concentration field around a growing crystal.
The formation of the primary α Phase and the secondary β phase in Sr(NO_3)_2-H_2O system following the dissolution of the β and ct phases in water, respectively, was observed in situ. From the large difference of the peritectic temperature and the temperatures at which such phenomena occur, it follows that the differences in the equilibrium concentration of the tow solid phases in a solution drives the formation of the stable phases.
In-situ observation microscope up to about 3000 magnifications has been developed to observe crystal growth from high temperature solution up to 1500 degree, and alite crystal growth from high temperature solution is examined associated with its nucleation by using this microscope.
The effects of pH , Pb ion addition and overheating upon the width of the metastable zone against nucleation in the KCl aqueous solution were investigated. It was found that these conditions had large influence on the width.
20.8, 41.7 and 52.1wt% trehalose solutions were supercooled more than 10K and frozen rapidly. Phase separation of ice and trehalose-rich phase was observed every time. Structure of the frozen 52.1wt% trehalose solution was finer than that of the lower concentration solutions. This fine structure caused homogeneous melting of 52.1wt% trehalose solution.
The surface energy of single crystals of apatites was estimated by liquid contact angles using Wilhelmy method. We also adopted static drop method in order to make sure the reliability of Wilhelmy method.
In fat products, the polymorphism is the major factor to determine the physical properties as melting behavior and morphology. The ultrasonication shortened the induction time of crystallization of trilaurin. And the polymorphism of triaurin was measured by the in-situ observation using time-resolved X-ray diffaction by u sing synchrotron radiation source . The ultrasonication promoted form which was a stable form.
Effects of ultrasound irradiation on the cystallization behavior of tripalmitin/tristearin (PPP/SSS) mixture has been examined in terms of nucleation rate. It was confirmed that ultrasound irradiation accelerated the nucleation rate as measured by induction time for the occurrence of crystals and by the number of crystals nucleated.
Thermal behavior and crystallization structure of tritauroyl Glycerol (LLL) in O/W microemulsion were investigated. With decreasing average particle size, the melting peaks shifted lower temperature and phase transition et LLL in O/W microemulsion was accelerated. Crystallization temperature was not dependent on particle size of oil phase.
We investigated the mechanism of morphological formation of silver crystals produced by reduction of AgNO_3 With ascorbic acid in the presence of organic additives. Chelating agents induced further evolution of morphologies.
The growth interface of an orthorhombic crystal of hen egg-white lysozyme was observed with AFM. The morphology and motion of steps were observed on the (110) face of the crystal resolving in the unsaturated protein solution. The concentration dependence of step velocity was observed, which enabled to determine the solubility of the crystal.
The strengths of intermolecular contacts (macrobond) in four lysozyme crystal forms were estimated, which account for morphology of crystals by using PBC approach. The other features of macrobond, such as surface area of contact, polar coordinate representation of contact site. Coulombic interaction forces, and the surface energies on crystal faces have also been evaluated.
Tetragonal hen egg-White lysozyme crystals were grown by the solubility-gradient method. Laue topography using the synchrotron radiation was applied for the assessment of the imperfection of the grown crystals. Some defect images were clearly observed on the topographs. The identifications of the defects are presented.
Impurity effect was investigated on the crystallization of the hen egg lysozyme tetragonal crystals. From the X-rey diffraction data and the observation of the growth sector boundary, we found that quality of the crystals decreases with a decrease in the supersaturation.
In order to understand the effect of impurity depletion zone in microgravity, fluorescence labeled impurity distribution in a lysozyme crystal was measured quantitatively and nondestructively by confocal laser scanning microscopy. It was found that impurity concentration incorporated in a crystal was determined by the influx rate between impurity and lysozyme molecules.
A sealed AFM vessel with constant temperature unit (incubator) was developed in this work. The whole AFM equipment was put in the incubator and temperature was controlled at 15-25℃±0.5℃. The step velocity of HEWL crystal could be controlled and measured accurately by the temperature controlled AFM system.
Solubility and growth rates of the crystals of glucose isomerase under high pressure have been measured. The solubility significantly decreased with increasing pressure. The growth rates of (101) face of the crystals at 100 MPa (30℃) were slightly larger than those at 0.1 MPa at the same supersaturation.
We have made highly reliable calculation of surface free energy on the vicinal surface with adsorption. We have found that the interchange between the two ordered states with respect to the adsorption layer causes the first-order transition on the equilibrium crystal shape.
We study the vicinal surface with repulsively interacting adsorption statistical mechanically. We investigate the thermal step bunching and the adsorption mediated inter-step attractions, which have been found in the system of the vicinal surface with attractive interacting adsorbates.
We study drift-induced step wandering in a vicinal face of Si(001). With step-down drift, only step pairing occurs. With step-up drift, both step pairing and step wandering occur with a weak step repulsion, and only the step wandering occur with a strong step repulsion. The results agree with the observation of a Si(001) vicinal face.
We study step bunching induced by drift flow of adatoms. With alternation of anisotropic diffusion coefficient like a Si(001) vicinal face, the step bunching occurs irrespective of the drift direction. When we neglect evaporation of adatoms, step bunching with step-down drift is faster than that with step-up drift. With increasing the evaporation, the difference of growth rate becomes small.
We study the possibility of step wandering due to the asymmetry of diffusion field on the upper and the lower terraces caused by the structural difference of the terraces. We consider two systems which have a gap in the diffusion coefficient and in the lifetime for evaporation, respectively. We report characteristic features of the instabilities in the two systems.
We study the equilibrium shape of a heteroepitaxial island with a two-dimensional discrete lattice model. The aspect ratio of an island becomes larger as the magmitude of the elastic energy g or the number of atoms in an island n. increases. The optimum size changes from infinity to a finite value as g increases.
As desorption process from GaAS(001) surface under atmospheric pressure of hydrogen is investigated by ab initio clculation. The value of the activation energy obtained from the calculations is close to the experimental value by in situ gravimetric (GM) method during the (1×1) to (2×4) transition. Our results show that H-adsorbed (2×4) reconstructed surfaces exist under the H2 ambient, and then As atoms on the surface desorb from the surface as As_2H_2 molecules.
Thermodynamic analyses were carried out to understand compositional instability of InGaN/GaN and InGaN/InN in the MBE growth. In the thermodynamic analysis, contribution of lattice constraint from bottom layer was incorporated using enthalpy of mixing of InGaN/GaN and InGaN/InN, ΔH_m^<InGaN/GaN> and ΔH_m^<InGaN/InN>, which can be obtained by empirical interatomic potential calculations. The results suggest that compositional unstable region for InGaN/InN shifted toward Ga-rich side compared with that for InGaN/GaN. This implies that homogeneous InGaN thin films with large indium mole fraction is possible to form on InN substrate.
Semigrand canonical (SGC) Monte Carlo (MC) simulations were performed on the InGaN thin films pseudomorphic to the GaN and InN substrates to draw the alloy phase diagrams. We formulated the Gibbs-Duhem integration technique in the SGC ensemble to draw the binordal curves. We obtained miscibility gaps of high asymmetry reflecting the shape of the energy curves.
Molecular dynamics simulation was carried out to estimate the diffusion coefficient and the mechanism of diffusion with a constant pressure and temperature. The following results were obtained: (1) There is a little diffusion of a vacancy in solid GaAs. (2) The diffusion path of an interstitial arsenic atom is different from that of an interstitial gallium atom. (3) The diffusion coefficient of an interstitial arsenic atom is larger than that of an interstitial gallium atom.
Mote Carlo simulations were performed on the crystallization of hard spheres near the bottom of the system under several gravitational conditions. Comparison has been made with experimental results of a colloidal crystallization: snapshots of simulations are apparently quite similar to photos of experiments.
Monte Carlo simulation of a binary ideal solid solution crystal was done by the three models "Kink model, Step model and Surface model", and the difference between models was clarified to the relation between the growth rate and the distribution coefficient.
Seeding condition in dislocation-free CZ-Si crystal growth without necking was investicgated. Si crystals were grown without nechking using heavily B and Ge codoped Si seeds 1/2 inches in diameter under various temperature control. Dislocation-free Si crystals wale obtained when the melt temperature was higher during seeding the diameter immediate under the seeding interface was slightly smaller than the seed. Under this seeding condition, dislocation-free Si crystals 8 inches in diameter could be successfully grown without necking process.
We studied lattice misfit between the Ge/B co-doped Si seed crystal and the CZ-Si grown crystal. We found the critical lattice misfit between the seed and the grown crystal to avoid the generation of misfit dislocations was 1×10-4Å.
High-energy synchrotron-radiation X-ray topography has been applied to the observation of CZ-Si crystal ingots. This technique revealed the behavior of dislocations generated at the seed-grown crystai interface of the CZ-Si ingot grown using a heavily B-doped Si seed, and clarified the suppression of dislocation generation by use of heavily B and Ge codoped Si seeds. We conclude that the high-energy X-ray topography is very useful as the nondesructive inspection of Si ingots.
The surface tension of silicon melts have been studied by ring tensiometry technique with nitrogen addition. The surface tension has a tendency to decrease with adding nitrogen into the melts. This tendency means the decrease of surface energy of melts and crystals at high temperature. The surface energy decreases leads to the decrease of void (COP) size.