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Ice-crystal growth in supercooled water is one of the most familiar examples of phase-transition dynamics, playing essential roles in various natural phenomena on Earth. Despite its fundamental importance, the microscopic view at the elementary step level remains elusive. Here, using an advanced optical microscope, we find self-organization of elementary steps during ice-crystal growth, called step-bunching instability (SBI), driven by the competition between step dynamics, interfacial stiffness, and latent heat diffusions. We also find that the SBI transiently induces screw dislocations and resulting spiral growth in the late stage of the growth process. Furthermore, quantitative observations with a two-beam interferometer allow us to obtain insights into the relative importance of the various mechanisms of the step–step interactions. Our finding offers a significant clue to understanding the general mechanism of melt growth beyond ice-crystal growth, inseparably involving several broad research fields, including cryobiological, geophysical, and material branches.

We have developed the bulk growth technique to reduce threading screw dislocations (TSDs) by combining solution growth and PVT growth methods. More than 80 % of TSDs in original seed crystals were successfully converted to Frank defects on basal planes by the solution growth on 4° off C-face with Si-5at.% Ti solvent. After PVT growth on the as-grown surface of the conversion layer, TSDs in the original seed were successfully reduced. The presence of micrometer-size macrosteps in the initial stage of PVT growth is important to continue to propagate the converted Frank defects on basal planes during PVT bulk growth.

A non-destructive, fast and accurate extended defect counting method on large diameter SiC wafers is presented. Photoluminescence (PL) signals from extended defects on 4H-SiC substrates were correlated to the specific etch features of Basal Plane Dislocations (BPDs), Threading Screw Dislocations (TSDs), and Threading Edge Dislocations (TED). For our non-destructive technique (NDT), automated defect detection was developed using modern deep convolutional neural networks (DCNN). To train a robust network, we used our large volume data set from our selective etch method of 4H-SiC substrates, already established based on definitive correlations to Synchrotron X-Ray Topography (SXRT) [1]. The defect locations, classifications and counts determined by our DCNN correlate with the subsequently etch-delineated features and counts. Once our network is sufficiently trained we will no longer need destructive methods to characterize extended defects in 4H-SiC substrates.

Shifts in the spatial distribution of threading dislocations in 150 mm 4H SiC wafers were examined as a response to intentional changes in both the flow of the nitrogen source gas used to control resistivity during bulk crystal growth, and the growth rate. The density of threading edge and screw dislocations was found to be more evenly distributed in wafers produced under a high-growth rate, low-resistivity process. This result corresponded to a flattening of the resistivity distribution, and a ~34% reduction in on-and off-facet resistivity differential. The effect was attributed to regularized 4H island coalescence due to modulation of step terrace width.

Body-centered cubic (BCC) metals, extensively utilized in low-alloy high-strength steels and heat-resistant alloys, exhibit a pronounced ductile–brittle transition (DBT) at cryogenic temperatures, marked by a well-defined yet narrow ductile–brittle transition temperature (DBTT) window. This paper overviews the research progress regarding the DBT mechanism of BCC metals. This mechanism was recently found to be related to the mobility of screw dislocation relative to edge dislocation, a decrease in which can induce a critical drop in the proliferation efficiency of dislocation sources. Furthermore, this paper summarizes the current research on the dilute solution softening effect of BCC metals, which has been frequently observed and studied in refractory alloys. The mechanism of this effect involves the low-temperature mobility of screw dislocations that could be promoted by specific solute atoms through kink pair nucleation. This offers a potential strategy for reducing the DBTT of low-alloy steels using a dilute solution, namely microalloying in metallurgy. However, the current understanding of the relationship between the macroscopic ductility of BCC alloys and the dilute solution softening effect is limited. This review aimed to draw attention to this relationship and strengthen related research.

We revisit the interaction between a point charge and an inhomogeneous magnetic field that yields the magnetic quantum dot system. This magnetic field is defined by filling the whole space, except for a region of radius r0. Then, we assume that there is an impenetrable potential wall located at r0 and discuss the quantum effects of screw dislocation topology and the missing magnetic flux. We first show that Landau levels can be achieved even though there is the presence of an impenetrable potential wall. We go further by discussing the confinement of a point charge to a cylindrical wire. In both cases, we show Aharonov–Bohm-type effects for bound states can be obtained from the influence of the screw dislocation topology and the missing magnetic flux. Later, we discuss the influence of the screw dislocation topology and the missing magnetic flux on the magnetization and the persistent currents.

The interaction between a screw dislocation and an elliptical hole with two asymmetrical cracks in a one-dimensional (1D) hexagonal quasicrystal with piezoelectric effect is considered. A general formula of the generalized stress field, the field intensity factor, and the image force is derived, and the special cases are discussed. Several numerical examples are given to show the effects of the material properties and the dislocation position on the field intensity factors and the image forces.

4H-SiC homo-epitaxial film was grown by adding HCl gas with a high Cl/Si ratio in CVD process, and defect formation and origin of the defect were investigated by confocal differential interference contrast (CDIC) microscope, PL imaging and normal differential interference contrast (DIC) microscope. It was found that a large number of large bumps are formed on the film grown at a high Cl/Si ratio of 30, and a large number of PL defects on bare substrate before the film growth are also observed. Coordinates where the bumps on the film are observed were good agreement with those where the PL defects on the bare substrate are observed. An etch pit sample on reproduced substrate from which epitaxial film was removed was fabricated by etching process using molten KOH+Na2O2, and some types of etch pits which might be originated from threading edge dislocations (TEDs), threading screw dislocations (TSDs) and basal plane dislocations (BPDs) in the substrate were observed. The coordinates where the etch pits on the reproduced substrate are observed were also good agreement with those where the bumps on the epitaxial film are observed. Therefore, it was clarified that a large number of the bumps abnormally grown on the epitaxial film are originated from the dislocations in the substrate.

The electroelastic problems of one-dimensional hexagonal piezoelectric quasicrystal materials with a periodic distribution of slant mode-III cracks under anti-plane shear and electromechanical loading are analyzed in this paper. Based on the three electrical boundary conditions at the crack surfaces, electrically permeable, electrically semi-permeable and electrically impermeable condition, the problems are classified as solving singular integral equations by using screw dislocation solutions. For two special cases of coplanar and parallel periodic crack arrays, the closed form solutions for the electroelastic fields, including stress fields, electric fields and tearing displacements, have been determined. The solutions of the singular integral equations for slant cracks can be transformed into the solutions of algebraic equations, the field intensity factors and mechanical strain energy release rates have been determined. The numerical solutions show that the normalized mechanical strain energy release rates increase under the influence of phonon field stress, phason field stress as well as electric fields, indicating that cracks are more likely to propagate in piezoelectric quasicrystal materials. In addition, it is found that the stress fields at the crack tips exhibited singularity, and the variation law of the total energy release rates with the applied electrical loading are also obtained.

In this paper, we present the quantum description that arose from the interaction of a moving magnetic quadrupole moment with electric field configurations in the background having a rotating frame of the presence of screw dislocation in the nonrelativistic regime. Interacting a moving particle involving a magnetic quadrupole moment with the chosen electric field configuration in a rotating frame can produce a kind of static scalar potential for the geometric background. We solve the relevant Schrödinger equation and acquire the exact solutions for that system by applying an analytical method. Besides, based on this interaction, owing to one of the choices for the electric field, we can see an Aharonov–Anandan quantum phase in the corresponding solutions.