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The nucleation and polymorphism of calcium carbonate have been studied using a microdevice named the crystallization mushroom. This setup allows carrying out precipitation experiments reproducibly by the vapor diffusion sitting drop technique. Within the range of concentrations investigated (from 10 to 500 mmol/L CaCl2 and from 1 to 25 mmol/L NH4HCO3), the dominant polymorph to appear first in the drops was calcite, or mixtures of calcite and vaterite followed by aragonite. Additionally, amorphous calcium carbonate (ACC) was not observed. The order of appearance of the polymorphs in the droplets is explained by intrinsic features of the crystallization mushroom, that is, the slow increase in the ionic activity product caused by slow diffusion of NH3 and CO2 gases, which favors the least soluble phase calcite to crystallize before other more soluble polymorphs. The appearance of calcite as the first nucleating dominant polymorph in the drops allowed us to calculate its surface free energy from induction ti...

We measured noninvasively step velocities of elementary two-dimensional (2D) islands on {110} faces of tetragonal lysozyme crystals, under various supersaturations, by laser confocal microscopy combined with differential interference contrast microscopy. We studied the correlation between the effects of protein impurities on the growth of elementary steps and their adsorption sites on a crystal surface, using three kinds of proteins: fluorescent-labeled lysozyme (F-lysozyme), covalently bonded dimers of lysozyme (dimer), and a 18 kDa polypeptide (18 kDa). These three protein impurities suppressed the advancement of the steps. However, they exhibited different supersaturation dependencies of the suppression of the step velocities. To clarify the cause of this difference, we observed in situ the adsorption sites of individual molecules of F-lysozyme and fluorescent-labeled dimer (F-dimer) on the crystal surface by single-molecule visualization. We found that F-lysozyme adsorbed preferentially on steps (i.e., kinks), whereas F-dimer adsorbed randomly on terraces. Taking into account the different adsorption sites of F-lysozyme and F-dimer, we could successfully explain the different effects of the impurities on the step velocities. These observations strongly suggest that 18 kDa also adsorbs randomly on terraces. Seikagaku lysozyme exhibited a complex effect that could not alone be explained by the two major impurities (dimer and 18 kDa) present in Seikagaku lysozyme, indicating that trace amounts of other impurities significantly affect the step advancement.

We review a wet chemical process to prepare the high quality hydrogen-terminated Si(111)-(1×1) surface and show that the two key issues for the high reproducibility are the etching time and the oxygen in the etching solution. We add ammonium sulfite to remove the oxygen according to the previous report [Appl. Surf. Sci. 130, 146 (1998)]. To elucidate the optimal etching time, the vibrational properties and the surface morphology are investigated by high-resolution electron-energy-loss spectroscopy (HREELS), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The HREELS spectra and images of AFM and STM reveal the precise aqueous NH4F etching process of Si(111) and indicate the high controllability of steps and terraces with atomic scale. The surface cleanliness and morphology strongly depend on the etching time. At the etching time of 10 min, we obtain an ultra-clean and atomically ordered surface with wide terraces of 36 ± 7 nm step distance. It is confirmed by AFM and STM that the 1.0% ammonium sulfite is useful to remove dissolved oxygen in the 40% NH4F etching solution and to prepare a high quality H:Si(111)-(1×1) surface with low density of etch pits. The measurement of scanning tunneling spectroscopy(STS) shows the Schottky diode character of the surface. This surface is well applied to the initial stages of the nano-particle and film growth of Ag atoms and Pentacene molecules. [DOI: 10.1380/ejssnt.2009.557]

The investigation of the effect of micro impurity on crystal growth by optical microscopy has been validated. The results showed that the growth rate of a lysozyme crystal was affected even if the concentration of impurity of fluorescent-labeled lysozyme (abbreviation, F-lysozyme) was very small. Different concentrations of F-lysozyme had different effects on crystal growth rate. The growth rate decreased much more as F-lysozyme concentration increased. The density of incorporated F-lysozyme on different grown layers of a lysozyme crystal during crystal growth was obtained from the results of flat-bottomed etch pits density. (C) 2008 Elsevier B.V. All rights reserved.

We have performed femtosecond laser-induced nucleation of protein in agarose gel to study the crystallization dynamics. The use of agarose gel facilitates the monitoring of laser-induced crystallization from the focal point, because the gel forms a highly viscous solution at low supersaturation and thereby suppresses the diffusion of laser-induced bubbles and microcrystals. We succeeded in monitoring the crystallization process from the focal point in the time range from microseconds to days. In addition, by combining an agarose gel system with fluorescence imaging, we revealed that the shrinking of laser-induced cavitation bubbles causes a local increase of protein concentration, which could be the trigger for protein nucleation.

The regulation of calcite mineralization by chiral biological molecules is one of the fundamental unresolved issues at the interface between biological, geological, and physical sciences. Here we address the role of chirality of l-aspartic acid (l-Asp), a model additive, in the regulation of the growth of calcite crystals. We apply phase-shift interferometry to nonintrusively monitor in-situ the morphology of the surface and quantify the velocity of propagation of the edges of the unfinished crystal layers, the steps, during crystallization. We show that l-Asp leads to several-fold increase in the step velocity, in all directions, at low supersaturations, and several-fold decrease in the step velocity at high supersaturations. l-Asp also introduces asymmetry in the velocity of steps related by mirror symmetry, however, of ≤10%. To explain the complex effects of l-Asp and, likely, of other biological regulators of calcite crystallization, we show that prior to incorporation into steps, calcium and carbonat...

We directly observed the transition of crystal growth behavior of Si in a low undercooling region. We succeeded in observing the initiation of faceted dendrite growth from a portion of parallel twins with increasing degrees of undercooling. The critical undercooling for growing a faceted dendrite was experimentally determined to be Δ T = 10 K. We also confirmed that parallel twins associated with faceted dendrite growth were formed between grain boundaries and not at grain boundaries during melt growth. The parallel-twin formation was explained in terms of a model of twin formation on the {1 1 1} facet plane at the growth interface.

We directly observed the diffusion of individual fluorescence-labeled protein molecules at an interface between a solution and a protein crystal using a single-molecule visualization technique, by which we can observe individual molecules with fluorescence labels. We simulated the diffusion behavior of mobile solute molecules at a solution−crystal interface, using fluorescence-labeled lysozyme and tetragonal lysozyme crystals. We found that the molecules diffused along the crystal surface 4–5 orders of magnitude slower (diffusion coefficient (6.9 ± 1.2) × 10−15 m2/s) than in a bulk solution, indicating that the molecules strongly interacted with molecules that were aligned at the crystal surface. This result denotes that slow two-dimensional diffusion inside a range of interactions from the crystal surface is a general picture of surface diffusion at an interface between an aqueous solution and a hydrophilic crystal surface. In addition, the number density of the molecules at the interface was 3 orders of...

We have investigated femtosecond laser-induced nucleation of hen egg-white lysozyme (HEWL) as a function of the laser pulse energy and pulse time width. This is the first recorded study to confirm that the femtosecond laser-induced nucleation of HEWL can be induced at a specific threshold laser energy. The threshold energy is comparable to that of cavitation bubble generation. The results strongly suggest that morphological changes in the solution are key factors for protein nucleation.

We observed two-dimensional (2D) nucleation behavior on {110} and {101} faces of tetragonal crystals of model protein lysozyme by laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM). We measured, for the first time directly and noninvasively, the 2D nucleation rates using 99.99% pure lysozyme, 98.5% pure lysozyme (Seikagaku Co.), and 99.99% pure lysozyme with intentionally added impure proteins (fluorescent-labeled lysozyme, covalently bonded dimer of lysozyme, and 18 kDa polypeptide). We found that 2D nucleation was the dominant growth mechanism under conditions adopted in this study, and the 2D nucleation occurred randomly on the entire crystal surface irrespective of supersaturation within the range of a = In(C/Ce) = 0-1.4, where C is a bulk lysozyme concentration and Ce the solubility (crystal size: 0.2-0.3 mm). Repeated 2D nucleation, which continued for 3-4 layers, was also observed mainly when the impure proteins were present. In addition, multilayered 2D islands were formed after the adsorption of relatively large foreign particles on the crystal surface. From the comparison between the 2D nucleation rates determined on the {110} faces with and without the impure proteins, we concluded that homogeneous 2D nucleation occurred under a higher supersaturation range (a > 0.8), irrespective of the presence of the impurities. In contrast, under a lower supersaturation range (σ < 0.8), we found that significant heterogeneous 2D nucleation dominated the growth mainly when the impure proteins were present. The {101} faces exhibited more significant heterogeneous 2D nucleation induced by smaller amounts of impurities than in the case of the {110} faces. We also determined the ledge free energies of the homogeneous and heterogeneous nucleation. Within the experimental conditions used in this study, we could not find significant dependence of the ledge free energies of the heterogeneous nucleation on the kinds of impure proteins.

We propose an improved wet chemical process for preparing a high-quality hydrogen-terminated Si(111)-(1× 1) surface and show an atomically ordered and ultraclean surface without carbon and oxygen contamination. The vibrational properties and surface morphology are investigated by high-resolution electron energy loss spectroscopy (HREELS), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). The HREELS spectra and images of AFM and STM reveal the precise aqueous NH4F etching process of Si(111) and indicate the high controllability of steps and terraces at the atomic scale. The surface cleanliness and morphology strongly depend on the etching time. At the etching time of 10 min, we obtain an ultraclean and atomically ordered surface with wide terraces of 36±7 nm step distance. It is confirmed by AFM and STM that 1.0% ammonium sulfite is useful for removing dissolved oxygen in the 40% NH4F etching solution and for preparing a high-quality H:Si(111)-(1× 1) surface with a low density of etch pits. The onset of tunneling current and the gap of 1.39 eV are measured by scanning tunneling spectroscopy. There is no peak at -1.3 eV in comparison with the previous report [Phys. Rev. Lett. 65 (1990) 1917].

Optical trapping of silver nanoparticles dispersed with rhodamine 6G (R6G) and NaCl in water gives surface-enhanced hyper-Raman scattering (SEHRS) of R6G. In this paper we have measured the SEHRS spectrum in the R6G concentration range between 10−7 and 10−11 M. SEHRS intensity and signal-to-noise ratio show clear differences at the lower R6G concentrations than ~10−9 M, indicating that the number of R6G in a trapped silver aggregate approaches the single-molecule level. This trapping SEHRS technique is applied for the detection of lysozyme molecules labelled with tetramethylrhodamine dye.

We propose a simple model to explain formation mechanism of parallel twins that are related to Si-facetted dendrite growth, and attempt to confirm its validity by in situ observations. The model involves the formation of a twin boundary at the {1 1 1} facet plane on the growth interface followed by formation of another twin parallel to the first one. Subsequently, a facetted dendrite grows parallel to the facet plane in this model. This growth behavior was successfully observed by growth experiments.

We investigate thin film crystals of an organic semiconductor, pentacene (Pn), grown on hydrogen-terminated Si(111) (H−Si(111)) surfaces with various interstep distances to elucidate the effects of vicinal steps of H−Si(111) on the growth of the Pn layers. By observing the morphology of the thin films with atomic force microscopy, we conclude that the vicinal steps induce significant anisotropy in the growth of the first layers of Pn: dendritic branches evolve in a lower-terrace side (the Si[112] direction), but a compact shape appears in an upper-terrace side (the Si[112] direction), although the first layers grow in an isotropic shape on a flat H−Si(111) surface. Furthermore, the growth of the first layers is much faster in the lower-terrace-side direction than in the upper-terrace-side direction. The anisotropy of the growth increases with decreasing interstep distances of H−Si(111), in particular ≤10 nm. Since such anisotropic growth was observed in a similar way irrespective of the directions of ...

We have experimentally determined the surface tension-to-shear viscosity ratio (the so-called characteristic velocity) of quasiliquid layers (QLLs) on ice crystal surfaces from their wetting dynamics. Using an advanced optical microscope, whose resolution reaches the molecular level in the height direction, we directly observed the coalescent process of QLLs and followed the relaxation modes of their contact lines. The relaxation dynamics is known to be governed by the characteristic velocity, which allows us to access the physical properties of QLLs in a noninvasive way. Here we quantitatively demonstrate that QLLs, when completely wetting ices, have a thickness of 9 +/- 3 nm and an approximately 200 times lower characteristic velocity than bulk water, whereas QLLs, when partially wetting ices, have a velocity that is 20 times lower than the bulk. This indicates that ice crystal surfaces significantly affect the physical properties of QLLs localized near the surfaces at a nanometer scale.

We demonstrate the oscillatory phenomenon for the twisting growth of a triclinic crystal through in situ observation of the concentration field around the growing tip of a needle by high-resolution phase-shift interferometry.

To study the effects of impure proteins, i.e. proteins with heterogeneous features that are minor constituents within “purified” protein solutions, on the crystallization of target proteins, and in particular the effects of such impurities on intermolecular contacts, we modified only the e -amino group of the N-terminal lysine of hen egg-white lysozyme with a fluorescent reagent, tetramethylrhodamine-5-isothiocyanate (5-TRITC), which has a high detection sensitivity. We then investigated the effects of the fluorescent-labeled lysozyme (F-lysozyme) on the nucleation and growth of tetragonal and monoclinic lysozyme crystals. In the tetragonal and monoclinic crystals, the fluorescent labels were located at molecular surfaces of lysozyme inside and outside of the intermolecular contact areas, respectively. We found that addition of a low concentration (0.02 mg/ml) of F-lysozyme significantly suppressed nucleation of the tetragonal crystals but had no effect on that of the monoclinic crystals. In contrast, addition of a higher concentration (0.05 mg/ml) of F-lysozyme significantly promoted the heterogeneous nucleation of both polymorphs. In addition, the decrease in the growth rate of the tetragonal crystal by F-lysozyme was much more significant than that of the monoclinic one, although the effective distribution coefficients of F-lysozyme for the tetragonal and monoclinic crystals were similar (2.9 and 3.2, respectively). These results clearly indicate that inhibiting the formation of specific intermolecular contacts plays a crucial role in the effects of impure proteins.

The step velocity on {1 1 0} faces of tetragonal lysozyme crystals has been measured in situ by high-resolution phase contrast microscopy. The movement of the steps shows a distinct anisotropy with respect to the growth velocity and the interaction with impurities. Under high-purity conditions (using lysozyme of 99.99% purity), the step velocity v step in the 〈1 1 0〉 direction exceeds the one in the 〈0 0 1〉 direction by a factor of 6. Spiral hillocks as well as 2D islands show an elongated, lens shaped morphology with pronounced tips in the 〈1 1 0〉 direction. The ratio of v step 〈1 1 0〉/ v step 〈0 0 1〉 is reduced to ≈2–4 when commercial grade lysozyme (purity: 98.5%) is used. The morphology of the hillocks/islands changes from the lens-shaped one to a rounded one. The step velocity into the fast growing 〈1 1 0〉 direction is significantly more affected by impurities than the growth into the 〈0 0 1〉 direction. The step velocity of monolayer islands (5.6 nm in height), of multilayer islands and of growth spirals is similar within the accuracy of the measurements. On the topside, the crystal is exposed to protein solution of ≈0.5 mm width. This results in convective mass transport conditions. On the backside of the crystal, there is a small gap of a few hundred nanometers. Within this gap, the crystal is growing under diffusive transport conditions. Changing the focus position from the topside of the crystal to the backside, the growth can be observed on the same crystal under convective as well as under diffusive conditions. Using commercial grade lysozyme, the growth velocity is higher under diffusive conditions than under convectively dominated ones. The morphology of the islands grown from a commercial grade solution under diffusive mass transport conditions is similar to the island morphology obtained otherwise only from high-purity solutions. Using high-purity solution, the step velocity and the island morphology does not differ as a function of the mass transport conditions. These results prove the extension of the depletion zone of the impurities and the reduced transport of impurities toward the growing interface under diffusive transport conditions.

We attempted to visualize defects in a tetragonal lysozyme crystal in situ by laser confocal microscopy combined with differential interference contrast microscopy (LCM-DIM). Birefringence microscopy (BM) and phase-contrast microscopy (PCM) were also employed for the in situ observations. LCM-DIM enabled us to observe the {1 1 0} surfaces of the crystals and visualize the strain fields around the dislocations normal to a light beam with sufficient contrast during growth for the first time. Relatively large inclusions (60 to 300 μm) inside the crystal could also be visualized during growth, with the use of BM and PCM. We found that the dislocations appeared in bundles and were probably generated at the periphery of the relatively large inclusions inside the crystal. The existence of the dislocations was confirmed by etching experiments, in which we observed two kinds of etch pits: those with a point bottom and those with a flat bottom; the former corresponded to the dislocations inside the crystal and the...

Liquid-phase epitaxial (LPE) growth on silicon carbide simultaneously covers macroscale defects, e.g. micropipes, and improves the quality of the crystal. In this study, an epi-layer grown over a macrodefect was evaluated by micro-Raman scattering spectroscopy. Before the growth process, the density of the stacking fault was high and the carrier density spatially inhomogeneous in the vicinity of the macrodefects. On the other hand, after growth, the layer over the macrodefect displayed good quality; the density of the stacking fault was less than that before growth and the homogeneity of the carrier density improved.

A novel method has been developed to improve protein-crystal perfection during crystallization in a high magnetic field and structural studies have been undertaken. The three-dimensional structure of orthorhombic hen egg-white (HEW) lysozyme crystals grown in a homogeneous and static magnetic field of 10 T has been determined and refined to a resolution of 1.13 angstroms and an R factor of 17.0%. The 10 T crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 56.54 (3), b = 73.86 (6), c = 30.50 (2) angstroms and one molecule per asymmetric unit. A comparison of the structures of the 0 T and 10 T crystals has been carried out. The magnitude of the structural changes, with a root-mean-square deviation value of 0.75 angstroms for the positions of all protein atoms, is similar to that observed when an identical protein structure is resolved in two different crystalline lattices. The structures remain similar, with the exception of a few residues e.g. Arg68, Arg73, Arg128 and Gln121. The shifts of the arginine residues result in very significant structural fluctuations, which can have large effects on a protein's crystallization properties. The high magnetic field contributed to an improvement in diffraction intensity by (i) the displacement of the charged side chains of Arg68 and Arg73 in the flexible loop and of Arg128 at the C-terminus and (ii) the removal of the alternate conformations of the charged side chains of Arg21, Lys97 or Arg114. The improvement in crystal perfection might arise from the magnetic effect on molecular orientation without structural change and differences in molecular interactions. X-ray diffraction and molecular-modelling studies of lysozyme crystals grown in a 10 T field have indicated that the field contributes to the stability of the dihedral angle. The average difference in conformational energy has a value of -578 kJ mol(-1) per charged residue in favour of the crystal grown in the magnetic field. For most protein atoms, the average B factor in the 10 T crystal shows an improvement of 1.8 angstroms(2) over that for the 0 T control; subsequently, the difference in diffraction intensity between the 10 T and 0 T crystals corresponds to an increase of 22.6% at the resolution limit. The mosaicity of the 10 T crystal was better than that of the 0 T crystal. More highly isotropic values of 0.0065, 0.0049 and 0.0048 degrees were recorded along the a, b and c axes, respectively. Anisotropic mosaicity analysis indicated that crystal growth is most perfect in the direction that corresponds to the favoured growth direction of the crystal, and that the crystal grown in the magnetic field had domains that were three times the volume of those of the control crystal. Overall, the magnetic field has improved the quality of these crystals and the diffracted intensity has increased significantly with the magnetic field, leading to a higher resolution.

Investigations on electromigration phenomena for protein crystallization in gels and solution using a crystal growth cell with multiple electrodes at constant current (2 μA per circuit) are discussed. In this work, the advantages and disadvantages of different electrode dispositions number, and electrode connections inside the cell are shown. A pH change effect was discarded as the main factor affecting the selective growth of the crystals at the cathode and the fact is explained in terms of electromigration phenomena. Additionally, controlled potential experiments were carried out in order to avoid parasitic reactions observed at constant current, resulting in an increase of reproducibility and better control of crystal growth.

On flat and off-cut Si(1 1 1) substrates terminated with monohydride, thin film crystals of organic semiconductor perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) were grown by molecular beam epitaxy (MBE) and were observed by atomic force microscopy (AFM). The thin film crystals on the hydrogen-terminated Si(1 1 1) surface (H–Si(1 1 1)) have a mesa-type island shape. On the flat H–Si(1 1 1) (average step distance >500 nm, off-angle

We investigated the grain growth behaviors of polycrystalline silicon during directional growth from melt. Two types of grain growth behaviors were directly observed using an in situ monitoring system. In the first, when the moving velocity of solid–liquid growth interface is slow and the interfacial morphology is flat, a grain with a plane of lower surface energy with respect to the growth direction expands to lateral direction. In the second, when the interface moves fast and it has an irregular shape because of the differences of the growth rate among grains, a faster growing grain competitively expands to lateral direction covering the slower one. We suggested that the undercooling at the growth front is the key parameter to divide those growth behaviors.

We investigated the effects of growth temperature on the surface morphology of silicon layers grown by liquid phase epitaxy method on a (1 1 1) oriented silicon substrate in a relatively low-temperature range from 600°C to 900°C using Au–Bi alloy solvent. Layers are formed in the following growth sequence: (1) commencing in the form of initial nuclei as starting points of growth, (2) these structures grow along lateral and vertical directions as island structures, and (3) coalesce each other. Moreover, it was made clear that flat layers tend to cover the substrate completely at high growth temperature, in order to clarify the main factor that influences the surface morphology, an empirical model of the growth process was constructed. As a result, the temperature dependence of the surface morphology mainly depends on the temperature dependence of the preferential growth direction of Si on Si (1 1 1).

In this work, the effects of an internal electric field (a direct current) on the crystallization of hen egg-white lysozyme were investigated. The crystallization was carried out in solution and gel placed in a crystallization cell. This crystallization growth cell has two parallel Pt electrodes (0.2 mm diameter and 15 mm length), and those electrodes were in contact with crystallization media. A direct current of 2.0 μA was applied (1.9×10 −3 V) for 8 h in solution and 12 h in gel media. During the crystallization, no generation of gas was observed. Lysozyme crystals appeared only around the cathode (negatively charged electrode), while amorphous precipitation was observed around the anode (positively charged electrode). By applying the direct current, the number of the deposited crystals was significantly decreased, and consequently the size of the crystals was increased. The direct current also decreased the induction time of nucleation. No significant change in pH was observed during the crystallization. The deposition of the crystals only around the cathode and the decrease in the induction time can be explained by an opposite polarity of the lysozyme molecules and the electrodes and by interactions between the lysozyme molecules and the Cl − in the vicinity of the electrodes. Electric potential generated by an electric field would be also responsible for the decrease in the number of the deposited crystals.

We fabricated Si-based solar cell with stacked Ge islands grown via the Stranski-Krastanov growth mode in the intrinsic layer of pin diodes. The onset of the external quantum efficiency in the near infrared regime was extended up to approximately 1.4 μm for the solar cells with stacked Ge islands. The quantum efficiency was found to increase with increasing number of stacking, showing that a part of electron-hole pairs generated within Ge islands was separated by the internal electric field and contributed to the photocurrent. Increase of the processing temperature for the impurity diffusion was found to bring blue-shift of the band gap through the intermixing of Si and Ge as well as the deformation of Ge islands. Therefore, low-temperature process was suggested to be necessary for further enhancement of quantum efficiency in the near infrared regime.

We report on fabrication of SiGe single crystal film on insulator by a simple approach including a growth of a thin Ge film on a commercially available SOI substrate, formation of a SiO2 protective layer, and rapid thermal annealing (RTA) in an Ar atmosphere. Homogeneity of the local Si fraction in SiGe-on-insulator (SGOI) was found to be closely connected with the SiGe phase diagram, and RTA below the solidus line is required to obtain homogeneous SGOI. In spite of the high annealing temperature beyond the melting point of Ge, obtained SGOI was revealed to be single crystalline as evidenced by electron back scattering pattern analysis.

Surface micro-topography of the {1 1 0} faces of tetragonal lysozyme crystals was observed in situ by laser confocal microscopy (LCM) combined with differential interference contrast microscopy (DIM). We could observe two-dimensional (2D) nucleation and subsequent growth of the 2D islands in real time. When steps of neighboring 2D islands coalesced, the contrast of the steps disappeared completely and the 2D islands merged smoothly. This result proved that the height of the steps observed by LCM combined with DIM was always the same and these steps were elementary ones (5.6 nm high). The combination of LCM and DIM was necessary to observe elementary steps with sufficient contrast. The elementary steps on a spiral growth hillock could also be observed using the LCM–DIM system, although their contrast was much smaller than that of the 2D islands because of much smaller inter-step distance.

Surface of an off-cut Si(1 1 1) substrate with an average step distance of 100 A was terminated with monohydride. On this substrate, thin film crystals of organic semiconductor PTCDA were grown by molecular beam epitaxy (MBE). Surface of the thin film crystals on the hydrogen-terminated Si(1 1 1) surface (H-Si(1 1 1)) were observed using ultra-high vacuum scanning tunneling microscopy (UHV-STM) and atomic force microscopy (AFM). The PTCDA thin film crystals had an island shape of Volmer–Weber type. From the direction of the vicinal steps of the substrate [1 1 0] , we determined the size and orientation of the PTCDA thin film crystals on the H-Si(1 1 1). Long-axis of the two-dimensional (2D) unit cell of the thin film crystals matches the vector (6, 2) of the H-Si(1 1 1) surface. We proposed two conceivable epitaxial relations: one is 6 2 2/3 11/3 and the other is point-on-line coincidence. 2D unit cells of the thin film crystals have widely stretched structure (2–10%), and the island growth of Volmer–Weber type is probably due to this large lattice misfit.

Novel effects of combining the magnetic and internal electric fields on protein crystallization were studied in this report. Homogeneity in crystal size and ratio of magnetically orientated crystals were significantly increased, when a homogeneous magnetic field of 10 T and an internal electric field (a direct current of 2 μA) were applied to the crystallization of hen egg-white lysozyme at the same time. When the directions of the magnetic field and the electric current were parallel, there were not significant effects observed. This result suggests that the Lorenz force is responsible for the coupling effects of the magnetic and internal electric fields.

Melt growth behavior of polycrystalline silicon was observed using a newly developed in-situ monitoring system consisting of a furnace and a microscope. It is possible to perform a directional growth from seed crystal or crucible wall and to observe the growth interface by using this system. Differences of growth rate or interfacial morphology among each grain of polycrystalline silicon were observed during melt growth. The Mullins–Sekerka instability of growth interface was also observed in a silicon melt for the first time. This observation system is confirmed to become a useful tool for revealing the growth mechanism of polycrystalline silicon.

Hydrostatic pressure is a useful parameter to control protein crystallization. One can change the solubility of protein crystals quickly by changing pressure. Information about the hydration of the specific surfaces of protein molecules can be obtained from the pressure dependency of solubility. When a protein molecule is hydrophobic or when its molecular volume in a solution is significantly larger than that in a crystal, applying high pressure is expected to be an effective method to promote crystallization. Pressure also affects the growth kinetics of protein crystals. Dependency of a growth rate on a driving force for crystallization was measured on typical proteins and analyzed using a two-dimensional nucleation growth model of a poly-nuclei type. High-pressure effects on growth kinetics could be explained by changes in a surface free energy, an activation energy and an average distance between kinks. Common understanding, however, has not yet been obtained for growth kinetics.

A magnetic field and high-pressure are effective parameters to control protein crystallization. A magnetic field significantly affects the number, orientation and growth rate (morphology) of protein crystals and damps the buoyancy convection in protein solutions. Quality of protein crystals can be also improved by a magnetic field. The improvement in the crystal quality is due to a magnetic orientation effect. High-pressure can also give large effects on the solubility and growth kinetics of protein crystals. Changes in the solubility with pressure results from a difference in the volume between bulk water and the water hydrating the contact regions of protein molecules inside the crystal.

The strain, surface and interface energies of the SiGe/Si (SiGe grown on Si) heterostructure system with and without misfit dislocations were calculated for the Frank–van der Merwe (FM), Stranski–Krastanov (SK) and Volmer–Weber (VW) growth modes essentially based on the three kinds of fundamental and simple structures. The free energies for each growth mode were derived from these energies, and it was determined as a function of the composition and layer thickness of SiGe on Si. By comparison of the free energies, the phase diagrams of the FM, SK and VW growth modes for the SiGe/Si system were determined. The (1 1 1) and (1 0 0) reconstructed surfaces were selected for this calculation. From the phase diagrams, it was found for the growth of SiGe on Si that the layer-by-layer growth such as the FM mode was easy to be obtained when the Ge composition is small, and the island growth on a wetting layer such as the SK mode was easy to be obtained when the Ge composition is large. The VW mode is energetically stable in the Ge-rich compositional range, but it is difficult for the VW mode to appear in the actual growth of SiGe on Si because the VW region is right above the SK region. The regions of the SK and VW modes for the (1 1 1) heterostructure are larger than those for the (1 0 0) one because the strain energy of the (1 1 1) face is larger than that of the (1 0 0) face. The regions of the SK and VW modes for the heterostructure with misfit dislocations are narrower than those for the one without misfit dislocations because the strain energy is much released by misfit dislocations. The phase diagrams roughly explain the behavior of the FM and SK growth modes of SiGe on Si.

We report on a theoretical investigation of the elastic strain in an ellipsoidal SiGe inclusion coherently embedded in Si and its influence on the band structure of SiGe. The strain was calculated as a function of the Ge fraction in SiGe and the aspect ratio of the ellipsoid, and utilized to derive the shift of the band edge. When the principal axis of the ellipsoid was chosen to be parallel to [001], the band structure of SiGe was predicted to be Si like regardless of the aspect ratio. The band gap of strained SiGe was also calculated, and the deviation of the aspect ratio from unity was found to be effective to decrease the band gap due to the breaking of the crystal symmetry. These results suggest the importance of controlling strain, shape, and local Ge fraction in multicrystalline SiGe, which we propose as a promising material for solar cell applications.

Solubility and growth rate of orthorhombic lysozyme (from hen egg-white) crystals were measured at 0.1 and 100 MPa. A growth or dissolution rate of a given concentration was measured, and the solubility was determined as the concentration at which the crystal did not grow or dissolve. The solubility decreased with increasing pressure at 30, 35 and 40 °C. This means that the supersaturation, σ (= lnC/C e, C: protein concentration, C e: solubility), increases; hence, the crystallization is enhanced with increasing pressure. The growth rates of (010) face, R(010), were replotted with σ, and the kinetic growth coefficients, k (= R(010) /σ), were estimated. The coefficient increased with increasing pressure at 30, 35 and 40 °C. This means that the growth kinetics is also enhanced_with increasing pressure.

In order to establish the general way to prepare thin film crystals of organic semiconductors, we studied annealing effects on the heteroepitaxial growth of Cu-phthalocyanine (CuPc) crystallites on KCl {0 0 1} substrate crystals. CuPc was deposited on a cleaved KCl single crystal by vacuum evaporation (under 10 −4 Torr). Then, the sample was taken out from the vacuum chamber and annealed in the air. On the CuPc as-deposited surface, no clear contrast was observed by scanning electron microscopy (SEM). On the contrary, many needle-like crystallites could be observed after the annealing treatment. Those crystallites were oriented so that their long axis was parallel to the 〈1 0 0〉 direction of the KCl substrate. We also investigated the effects of the annealing temperature and annealing duration time to find an optimal annealing condition.

We developed an automatic feedback control system of the crystal–melt interface position to keep the temperature at the interface constant during growth, and demonstrate its successful application to grow Ge-rich SiGe bulk crystals with uniform composition. In this system, the position of the crystal–melt interface was automatically detected by analyzing the images captured using in situ monitoring system based on charge-coupled-devices camera, and the pulling rate of the crucible was corrected at every 1 min. The system was found to be effective to keep the crystal–melt interface position during growth even when the variation of the growth rate is quite large. Especially, the interface position was kept for 470 h during growth of Ge-rich SiGe bulk crystal when we started with a long growth melt of 80 mm. As a result, a 23 mm-long Si 0.22 Ge 0.78 bulk crystal with uniform composition was obtained thanks to the constancy of the growth temperature during growth through the control of the interface position. Our technique opens a possibility to put multicomponent bulk crystal in a practical use.

In this article, recent advances in the fundamental research in the protein crystallization under high pressure were reviewed. Pressure is expected to be an important parameter to control protein crystallization, since hydrostatic pressure affects the whole system uniformly and can be changed very rapidly. So far, a lot of studies of protein crystallization under high pressure have been done, some less systematic than others. We have particularly focused on fundamental aspects (the solubility and the crystal growth kinetics) of protein crystallization under high pressure. The studies reviewed contribute significantly to high-pressure crystallography and high-pressure protein science.

We report on growth and characterizations of Si/multicrystalline-SiGe (mc-SiGe) heterostructure as a promising candidate to surpass mc-Si solar cells. Spatial distribution of the status of strain in Si was investigated using microscopic Raman spectroscopy. The strain was found to be strongly influenced by the composition and microstructure of underlying mc-SiGe. Spatial variation of the strain as well as strain relaxation was found to be suppressed by decreasing average Ge composition of underlying SiGe.

The intrinsic diffusion coefficients in a liquid GaGe alloy were determined using a novel method based on Fick’s first law. The mutual and self diffusion coefficients also were derived. The intrinsic diffusion coefficients of both components are similar to each other and so both components equally contribute to the mutual diffusion coefficient. Also, the values of the self diffusion coefficient agree with values reported in the literature. A comparative study of the gallium self diffusion coefficients between the GaGe and GaZn systems indicated that the self diffusion coefficient depends on the second alloy component.

Crystal growth behavior of silicon melt was observed using a confocal scanning laser microscope with an infrared image furnace. The morphology of the growth interface changed from planar to facet with increasing growth rate. The facet vanishing process was also observed. It was shown the (1 1 1) facet formed at a steady state. The undercooling in front of the facet interface was measured by an infrared camera and found to be almost 7°. The growth behavior of silicon melt was explained by an analytical expression based on a two-dimensional nucleation model.

BphC derived from Pseudomonas sp. strain KKS102 is an extradiol-cleaving catecholic dioxygenase. This enzyme contains a non-heme iron atom and plays an important role in degrading biphenyl/polychlorinated biphenyls (PCBs) in the microbe. To elucidate detailed structures of BphC reaction intermediates, crystal structures of the substrate-free form, the BphC–substrate complex, and the BphC–substrate–NO (nitric oxide) complex were determined. These crystal structures revealed (1) the binding site of the O 2 molecule in the coordination sphere and (2) conformational changes of His194 during the catalytic reaction. On the basis of these findings, we propose a catalytic mechanism for the extradiol-cleaving catecholic dioxygenase in which His194 seems to play three distinct roles. At the early stage of the catalytic reaction, His194 appears to act as a catalytic base, which likely deprotonates the hydroxyl group of the substrate. At the next stage, the protonated His194 seems to stabilize a negative charge on the O 2 molecule located in the hydrophobic O 2 -binding cavity. Finally, protonated His194 seems to function as a proton donor, whose existence has been proposed.

Multicrystalline SiGe (mc-SiGe) with microscopic compositional distribution, which has been proposed as a promising material for solar cell applications, was characterized by microscopic Raman spectroscopy. As expected, a strong spatial variation of Raman spectra was observed. However, the compositional distribution obtained by a separate energy-dispersive X-ray analysis did not fully explain the observed spatial variation of Raman spectra. A plausible explanation of the inconsistency is the existence of built-in strain, which originates from the lattice mismatch between Si and Ge.

The growth technique and physical properties of SiGe multicrystals with microscopic compositional distribution are demonstrated for new high-efficiency solar cells in which the wavelength dependence of the absorption coefficient can be freely designed by controlling the compositional distribution in the SiGe multicrystals. This growth technique is suitable for the practical casting method, and it is made up of melt growth of SiGe multicrystals with wide and microscopic distribution of the composition from Si to Ge all over the crystals. It is studied how much widely the microscopic compositional distribution in SiGe multicrystals grown from binary Si–Ge melts can be controlled by the melt composition and the cooling process. The range of the microscopic compositional distribution becomes wider as the starting Si concentration in the growth melt becomes larger. SiGe multicrystals with various microscopic compositional distribution can be freely controlled by optimizing the melt composition and the cooling process. The wavelength dependence of the absorption coefficient of such SiGe multicrystals can also be freely designed. Using the experimentally determined absorption coefficient of a SiGe crystal with microscopic compositional distribution, the short circuit photo-current of solar cells was calculated and it is demonstrated that the short circuit photo-current can be much larger for SiGe with microscopic compositional distribution than for SiGe with uniform composition. Si thin film can be easily grown on such a SiGe multicrystal and the Si/SiGe heterostructure can be obtained. These results show that SiGe multicrystals with microscopic compositional distribution are hopeful for new high-efficiency solar cell applications by using the practical casting method.

We established an in situ and simultaneous measurement system for solute distribution and temperature distribution in high-temperature solutions. The system consists of an infrared camera, an X-ray fluorescence spectrometer for concentration measurement and a sample stage with a two-zone heater. A sample holder is composed of some graphite parts with a quartz glass window at the bottom of holder for monitoring the infrared image. Concentration measurements are performed by the X-ray analysis through the graphite lid at the top of the holder. The present system was applied to the in situ measurement of the solute and temperature distributions in the gallium–zinc solution during the crystal growth by the solute supplied zone melting method. We selected the thin sample with the thickness of 500 μm to observe the solute distribution characterized by diffusion process. As a result, we successfully observed the process in which the solute distribution changed and consequently reached the stationary state due to the diffusion in the linear temperature gradient. These results show that the present system can be a powerful tool for actual survey of supercooling and supersaturation.

Solubility of glucose isomerase (from Streptomyces rubiginosus) crystals was measured in situ at 0.1 and 100 MPa. An equilibrium temperature of the crystal with the solution of a given concentration was measured using a two-beam interferometer. The solubility of the crystal decreased to about one-ninth with increasing pressure from 0.1 to 100 MPa at 30 °C. This means that the supersaturation, σ (= ln C/Ce, C = protein concentration, Ce = solubility), increases significantly with increasing pressure at the same temperature. This strongly suggests that the substantial acceleration of the crystallization of glucose isomerase with increasing pressure reported by Visuri et al. is due to the significant decrease in the solubility. The enthalpy and entropy of the dissolution were estimated from the van't Hoff plots. The volume change accompanying the dissolution took a large positive value as ΔV = 54 ± 31 cm3 mol-1 at 30 °C.