Two-dimensional graph model for epitaxial crystal growth with adatoms

Crystalline silicon thin film solar cells on glass substrates are a low cost alternative to silicon wafer cells. As an alternative to a simple furnace annealing step in which a-Si is converted to c-Si with 1 µm grains, an epitaxial crystal growth process is presented here. First a seed layer is prepared on glass by diode laser crystallization of an a-Si layer on glass to result in 100 µm grains. Then a-Si is deposited on top of the seed which is converted to c-Si by epitaxial growth. A 1.1 µm thick c-Si layer with 100 µm grains was produced in this way. The paper presents details of the epitaxial growth process.

Quantum light from optically dressed quantum dot states in microcavities

Diopside has been developed for use in dental root implants and for the filling of bone defects. In previous studies, diopside developed hydroxyapatite (HA) on its surface and achieved a direct bond with bone. The purpose of this study was to investigate the mechanism of crystal formation on the diopside surface. We ultrastructurally evaluated the interface between new diopside-induced crystals and diopside. Specimens were prepared in three experiments: (1) Granular diopside was immersed in simulated body fluid (SBF); (2) granular diopside was implanted into a cavity in rabbit bone; and (3) a diopside dental root implant was implanted into a Japanese monkey. The specimens were examined by contact microradiography, high-resolution transmission electron microscopy, and analytical electron microscopy. In the experiment with SBF, many platelet-like crystals formed in the diopside surface layer. The lattice of diopside and that of the new crystals were very close, but no clear continuation of the lattice was observed. In the experiments which used a rabbit and a monkey, contact microradiography showed close contact between bone and diopside. High-resolution transmission electron microscopy revealed crystal growth from the diopside surface layer, and continuity between the diopside lattice and that of the new crystals. The morphological characteristics of the new crystals and the results of these analyses suggest that these new crystals are HA. With regard to the mechanism by which crystals are formed on the diopside surface layer, it is possible that epitaxial crystal growth could originate as a nucleus on the surface. In this case, epitaxial crystal growth of primarily octacalcium phosphate (OCP) may have occurred, and this may have changed to HA by a phase transition. However, epitaxial growth of OCP on the diopside surface is still highly speculative, since there is no direct supporting evidence.

A kinetic model of epitaxial growth on a Ga-stabilized GaAs (001) surface from As4 and Ga beams is proposed. Elementary surface processes are studied: adsorption-desorption of As4, bimolecular reaction of As4*, and incorporation of As 2 chem in lattice sites. The model correctly describes the experimental results for the growth rate at low and high As4 pressures. The role of As4 desorption from the surface in the epitaxial growth of GaAs crystals is analyzed.

We investigated the crystal growth of piperonyl (E,E)-muconate [bis(3,4-methylenedioxybenzyl) (E,E)-muconate, MDO] on inorganic crystalline substrates during vapor deposition for the control of polymer chain alignment by the subsequent solid-state photopolymerization of the MDO monomer thin films deposited on the substrate. We controlled the arrangement of the MDO molecules and the polymer chains produced on the substrate, depending on the lattice parameters of the substrate surfaces used. The epitaxial crystal growth of MDO on the {001} plane of a KCl single crystal was observed under the condition that the crystal lattice lengths of MDO agreed well with the specific space distance of the substrate; i.e., the KCl cubic crystal resulted in a d(110) value of 4.45 Å, which was very close to the value of the monomer stacking distance in the MDO crystal (d(s) = 4.43 Å). On the other hand, slightly large and too small d(110) values for KBr and NaCl, respectively, resulted in the less controlled and no epitaxial crystal growth of MDO. The irradiation of polarized UV light on the MDO thin-film crystal produced highly regulated polymer alignment in a specific direction on the KCl substrate.

Kinetics model of crystal nucleation and growth in supercooled water for designing ice-templating soft matter scaffold

Epitaxial heterostructures with precise registry between crystal layers play a key role in electronics and optoelectronics. In a close analogy, performance of nanocrystal (NC) based devices depends on the perfection of interfaces formed between NC layers. Here we systematically study the epitaxial growth of NC layers for the first time to enable the fabrication of coherent NC layers. NC epitaxy reveals an exceptional strain tolerance. It follows a universal island size scaling behaviour and shows a strain-driven transition from layer-by-layer to Stranski-Krastanov growth with non-trivial island height statistics. Kinetic bottlenecks play an important role in NC epitaxy, especially in the transition from sub-monolayer to multilayer coverage and the epitaxy of NCs with anisotropic shape. These findings provide a foundation for the rational design of epitaxial structures in a fundamentally and practically important size regime between atomic and microscopic systems.

Scanning tunneling microscopy (STM) and conventional electrochemical techniques were utilized to investigate the growth kinetics and mechanism of palladium island electroformation on highly oriented pyrolitic graphite (HOPG) from aqueous acid palladium chloride solutions at 298 K. Initially, the electrodeposition reaction at low cathodic overpotentials involves an activation process in which a PdCl2 surface intermediate is formed. At intermediate overpotentials, the growth of palladium islands involves a progressive nucleation and growth model under diffusion control, whereas at high overpotentials, the bulk discharge of soluble palladium species undergoes a free convective-diffusion process. As the cathodic overpotential is shifted negatively, the aspect ratio of the islands, defined as the ratio of the maximum height of the island to the island radius, and the island size decrease, whereas the island density increases. As the cathodic overpotential becomes a few millivolts more positive than the thresho...

Polyoxymethylene (POM) exhibits high crystallinity, dimensional stability, and low friction, yet its intrinsic brittleness and limited impact resistance restrict its use in dynamic environments. Blending POM with thermoplastic polyurethane (TPU) introduces molecular-level interactions particularly hydrogen bonding between carbonyl and urethane groups that generate a constrained amorphous interphase with semi-reversible physical crosslinks. This interphase governs secondary relaxations (α′/β) and segmental dynamics, enabling efficient energy dissipation and enhanced damping behavior. This review provides a comprehensive and critical synthesis of POM/TPU hybrid systems from a macromolecular physics perspective, emphasizing interfacial adhesion mechanisms, morphology evolution, and crystallization kinetics. The influence of compatibilizers, chain extenders, and fillers such as glass fibers, montmorillonite, and nano-calcium carbonate (CaCO3) is analyzed in tailoring phase dispersion, epitaxial crystal growth, hierarchical microstructure, and multi-scale toughening mechanisms. Comparative insights with other POM-based blends (e.g., POM/EPDM, POM/SEBS, POM/ABS, POM/PA6) further elucidate structure–property correlations and performance tradeoffs. The interplay between processing parameters, interphase architecture, and viscoelastic response is highlighted to establish a processing–structure–property framework. Finally, emerging opportunities in sustainable fillers, additive manufacturing, interfacial engineering, and data-driven multi-scale modeling are discussed as pathways toward next-generation, impact-resistant and recyclable acetal-based composites for lightweight engineering applications.

Cadmium Zinc Telluride (CD1-xZnxTe has become a crucial material for x-ray and gamma ray detection due to its wide band-gap, high atomic number and high density, which offer high efficiency and sharp spectroscopic resolution at room temperature. In addition, due to being lattice matched, it can also be used as substrate for the epitaxial growth of HgCdTe that can be used for infrared detection with high resolution. Hence, increasing the single crystal yield of CdZnTe from the grown ingot gained importance for the development of such detectors. In this study, a combination of modeling and experimental approaches has been developed in order to obtain high quality CdZnTe bulk crystals with good single crystal yield. A multi-zone Vertical Gradient Freeze (VGF) furnace was used for CdZnTe growth experiments. A global temperature model of the multi-zone furnace including complete geometry was employed using CrysMAS crystal growth modeling software. The correlation studies between the model and experimental behavior of the furnace are discussed in order to create a reliable model for temperature predictions. Temperature models were also included solid-liquid interface study in order to observe the interface shape at various stages of growth which would provide valuable insight about the quality and the yield of the ingot. Growth parameters and crucible geometries were estimated by CrysMAS simulations and interchanged between experiments. Effectiveness of temperature models and simulations was supported by experimental results such as single-crystalline yield, grain evolution and crystalline quality comparison by DCRC measurements of five successful crystal growths with moderate single crystal grain sizes.

A certain model for epitaxial film growth has recently attracted attention, with the existence of small global solutions having being proved in both the case of the n-dimensional torus and free space. We address a regularity question for these solutions, showing that in the case of the torus, the solutions become analytic at any positive time, with the radius of analyticity growing linearly for all time. As other authors have, we take the Laplacian of the initial data to be in the Wiener algebra, and we find an explicit smallness condition on the size of the data. Our particular condition on the torus is that the Laplacian of the initial data should have norm less than 1/4 in the Wiener algebra.

The effects of interruption time on the growth of Ge islands prepared by ion beam sputtering deposition

This chapter is a survey of recent work on the freezing and thawing of food and other biological materials when compounded by other phenomena: mass transfer, supercooling and nucleation, crystal growth, high pressure, convection in liquid foods, microwave and radio frequency heating, and mechanical effects (stresses and cracking) due to expansion. A detailed mathematical model is presented for moisture transfer in both dense and porous foods, as it is an important phenomenon. For cases when supercooling, nucleation and crystal growth have important effects, three nucleation models are discussed, each applicable to a different type of material: instantaneous nucleation followed by dendritic crystal growth, gradual nucleation in an emulsion (butter) and nucleation-propagation in cellular tissues. The modelling of crystal growth has been carried out in other fields than food, using one of the following methods: enthalpy method, cellular automata, front tracking methods, level set method and phase field method. To model microwave and RF thawing, Lambert’s law can be used when the product thickness exceeds a critical value compared to the wavelength; else the electromagnetic equation based on Maxwell’s equations must be solved. The expansion of water when turning into ice may cause severe mechanical strains and stresses, and possible cracking. Many of these topics have not been investigated in detail by food researchers and there is a need for further studies.

CFD modelling of single crystal growth of potassium dihydrogen phosphate (KDP) from binary water solution at 30 °C

Porous materials are of high importance, a.o. in the field of catalysis. A typical example of relevant and well-known crystalline, microporous materials is zeolites. These stable aluminosilicates possess tuneable Lewis and Brønsted acidity, in combination with microporous channels and/or cages allowing for size and shape selectivity. As a result, these zeolites are used for many catalytic applications, including large industrial processes such as fluid catalytic cracking (FCC). Another class of highly crystalline porous solids, namely metal-organic frameworks (MOFs), have gained a lot of attention over the last few decades. These materials, built-up of metal nodes and organic linkers, are interesting due to their huge versatility: material properties, such as pore size and Lewis acidity, can be tuned to its specific application by simply tailoring its building blocks. Comparable to zeolites, MOFs can be used for a wide range of applications, such as catalysis, separation and in electronic (sensing) devices. Of both zeolites and MOFs, a large number of framework structures are known. Most of these compounds have been developed through the process of trial-and-error and/or educated guesses. Ultimately, one wishes to apply true rational design to the development of catalysts for novel applications. The required fundamental understanding of crystal growth needed for such purposes is unfortunately still lacking in literature. To study nucleation and growth behaviour, a model system apt for near-field characterisation is needed. As a result, 2D thin-film structures have been developed to facilitate high control over, and easy analysis of, crystal growth. Additionally, by converting these porous materials into thin-films, the gate-way to (membrane) specific applications is opened. To gain fundamental insights into catalytic thin-films, and to establish structure-performance correlations, we apply multiple (in-situ) characterization techniques. Initially, hetero-epitaxial growth processes were probed to uncover crystal nucleation and growth mechanisms. This real-time in-situ research was performed on HKUST-1 surface-mounted MOFs, or SURMOFs. During a one-pot synthesis between metal-ions and linkers, the surface topology was continually measured using atomic force microscopy (AFM). On a single (10 x 10 µm2) AFM spot we could follow the formation of MOF islands over multiple timeframes. Using a tailor-made script, these (growing) islands were labelled and tracked over all timeframes. From this, a (temperature-dependent) growth rate could be established. Next to structural information, the chemical nature of the formed MOF grains was uncovered using infra-red reflection absorption spectroscopy (IRRAS) at grazing angles, a highly sensitive technique providing data from monolayer coverage and up. Additionally, a novel photo-induced force microscopy (PiFM, or AFM-IR) technique was applied to these SURMOFs, which is able in distinguishing grain specific chemical nature of the nm-sized MOF islands. This knowledge of nucleation and growth behaviour can be applied to the production of high-quality SURMOFs. Whereas the direct synthesis provides a facile medium for in-situ AFM investigations, a layer-by-layer synthesis offers high control over SURMOF fabrication quality. This synthesis, in which the growth phases of the inorganic and organic compounds are separated, is a perfect model system for the systematic study of growth parameters and their effect of resulting SURMOF quality. Using IRRAS, we can fully identify peaks in the HKUST-1 SURMOF spectrum, including precursor species, which were previously unknown in literature. Additionally, in contrast to previously posed growth mechanisms, our (AFM-)IR studies show growth to occur through a solution-mediated mechanism. Moreover, AFM-IR can be used to directly probe defect formation on the nm-scale, allowing for catalytic structure-performance correlations. In accordance with the found mechanism, existing synthesis procedures can be optimized in terms of quality and speed. For zeolite ZSM-5, an innovative approach to enhance catalytic performance is to prepare homo-epitaxially grown zeolite ZSM-5 as continuous, oriented films with accessibility to only the straight zeolite channels. Applying advanced characterization techniques, such as tip-enhanced Raman spectroscopy (TERS), single-molecule fluorescence microscopy as well as grazing incidence characterization methods, we can explore the synthesis mechanisms, as well as study 3-D diffusion and related reactivity through a single pore orientation of zeolite ZSM-5 down to the level of a single molecule. Furthermore, we show the methanol-to-hydrocarbons reaction on ZSM-5 thin-films can be studied with AFM-IR. AFM-IR is highly sensitive to the surface chemical structure with regards to Al3+ framework incorporation as well as hydrocarbon formation, providing a more complete nanoscale picture of the structural and catalytic information. These combined case studies show the strength of microscopy and spectroscopy tools in understanding and improving catalytic materials. Figure 1