Progress in Crystal Growth and Characterization of Materials最新文献

Epitaxial semiconductor quantum dots have been, in the last 40 years or so, at the center of the research effort of a large community. The focus being on “semiconductor physics and devices”, in view of the broad applications and potential, e.g., for efficient temperature insensitive lasers at telecom wavelengths, or as “artificial atoms” for quantum information processing. Our manuscript aims at addressing, with an historical perspective, the specifics of (III-V) epitaxial quantum dot early developments (largely for light emitting) and subsequent years. We will not only highlight the variety of epitaxial structures and methods, but also, intentionally glancing a didactic approach, discuss aspects that are, in general, little acknowledged or debated in the present literature. The analyses will also naturally bring us to examine some of current challenges, in a field which, despite sensational achievements, is, remarkably, still far from being mature in its developments and applications.

Magnesium borate (Mg₂B₂O₅) whiskers are highly regarded as a promising inorganic reinforcing material due to their availability, ease of preparation, and remarkable reinforcing effect. The main objective of this article is to examine the properties of Mg₂B₂O₅ whiskers and to encourage researchers to utilize them, thereby enhancing the characteristics of various composites in a cost–effective manner. Six production methods of Mg₂B₂O₅ whiskers are addressed, and based on these methods, different growth mechanisms of Mg₂B₂O₅ whiskers, including liquid–solid, solid–liquid–solid, vapor–solid, and vapor–liquid–solid mechanisms, are analyzed and summarized. As reinforcing materials, Mg₂B₂O₅ whiskers are widely employed in alloys and polymers, effectively enhancing the physical and chemical properties of the resulting whisker–reinforced composites, including mechanical, friction and wear resistance, and flame retardancy properties. Furthermore, the impact of surface modification of Mg₂B₂O₅ whiskers on the properties of composites was explored. The cost–effectiveness, favorable properties, and wide availability of Mg₂B₂O₅ whiskers make them excellent potential materials for numerous applications, and the article provides an analysis and forecasts the future development direction and prospects of Mg₂B₂O₅ whiskers.

In this review article, we focus on the synthesis process and properties of Fe-Si-B-based soft magnetic alloys that exhibit superior magnetic properties. The process parameters related to the synthesis and characterization of these types of alloys are studied widely and investigated the properties observed in nanocrystalline Cu and Nb-dopped Fe-Si-B-based magnetic alloys. The properties of these materials are an exceptional combination of high permeability, high Curie temperature, low core losses and anisotropy energy, and near zero effective magnetostriction suitable for various applications such as magnetic field sensors, sensors for non-destructive evaluation of materials, motors, transformer cores, electric vehicles, etc. A significant number of research works have been conducted so far and more research is continued to improve their properties in various ways including engineering of materials composition, optimization of synthesis processes, and parameters for easy integration into modern devices. This review article aims to demonstrate a comparison study of the properties of Fe-Si-B- based soft magnetic alloys and to provide the latest updates on their developments toward tailoring the extrinsic (coercivity, and permeability) and intrinsic (Curie temperature and saturation magnetization) properties for conquering the subsequent area of applications.

Under alkaline conditions, silica forms self-assembled mineral compounds which are similar in morphology, nanostructure, and texture to the hybrid biomineral structures that, millions of years ago gave to life. In this review we propose that, during the earliest history of this planet, there was a geochemical scenario that led to large-scale production of both simple and complex organic compounds, many of which were important for prebiotic chemistry. The production was based on a high concentration of silica and high pH. Two main factors affected this process: a) a source of simple carbon molecules that were either synthesized abiotically from reactions associated with serpentinization, or carried by meteorites and produced by their impact on Earth, and b) the formation of self-organized silica-metal mineral compounds that catalyzed the condensation of single molecules in a reduced methane-rich atmosphere. We discuss the plausibility of this geochemical scenario and its catalytic properties and the transition towards a slightly alkaline to Neutral Ocean.

Step pattern stability of the vicinal surfaces during growth was analyzed using various surface kinetics models. It was shown that standard analysis of the vicinal surfaces provides no indication on the possible step coalescence and therefore could not be used to elucidate macrostep creation during growth. A scenario of the instability, leading go macrostep creation, was based on the dynamics of the step train, i.e. the step structure consisting of the high (train) and low (inter-train) density of the steps. The critical is step motion at the rear of the train which potentially leads to the step coalescence i.e. creation of the double and multiple step. The result of the analysis shows that the decisive factor for the step coalescence is the step density ratio in and out of the train. The ratio lower than 2 prevents double step formation irrespective of the kinetics. For higher ratio the coalesce depends on step kinetics: fast incorporation from lower terrace stabilizes the single steps, fast incorporation from upper leads to step coalescence. The double step is slower than the single steps, so the single steps behind catch up creating multistep and finally macrostep structure. The final surface structure consists of the macrosteps and superterraces, i.e. relatively flat vicinal segments. The macrostep alimentation from lower superterrace leads to emission of the single steps which move forward. Thus the single step motion is dominant crystal growth mode in the presence of the macrosteps. These steps finally are absorbed by the next macrostep. The absorption and emission of single steps sustain the macrostep existence, i.e. the macrostep fate is determined the single step dynamics. The condition for single step emission was derived. In addition, the macrosteps are prone to creation of the overhangs which results from surface dynamics coupling to impingement from the mother phase. The angular preferential access of the bulk material to the macrostep edge, leads to the overhang instability and creation of inclusions and dislocations.

This article highlights the electrodeposition of metals, in crystalline or amorphous form, that are monentous in the present era of science and technology. Available literature related to nucleation and growth of metal crystals has been reviewed to gain insight into the mechanism and kinetics. The progress made in the electrodeposition technique, using an ionic liquid (IL) medium, has been detailed for selected metals using different ILs for achieving the controlled growth mechanism driven by electrochemical potential. Theoretical models for nucleation and growth of crystals by electrodeposition have been explained and the effect of crystallization overpotential on the growth of crystal growth has been discussed. Finally, the factors affecting the growth process and the mechanism have been identified and critically analyzed based on the available literature, fundamental knowledge-base, chemistry of ILs, and electrodeposition.

The crystallization technique where an electric field is applied is an extremely powerful tool to control the crystallization processes of various materials. In particular, the method with application of an external electrostatic electric field can have a significant effect on the phase equilibrium of the liquid and solid phases. This review demonstrates that the crystallization processes of proteins are significantly impacted by the application of an external electrostatic electric field: (1) Control of both the increase and decrease in the nucleation rate can be achieved by changing the applied frequency of the external electrostatic electric field. (2) The effect of the external electrostatic electric field on the nucleation rate can be controlled by regulating the thickness of the electric double layer (EDL) formed at the interface. (3) The quality of the grown crystals can be improved by an increase in the step free energy under application of an external electrostatic electric field at 1 MHz. The effect of the external electrostatic electric field on nucleation and growth kinetics during crystal growth of proteins is also discussed based on a thermodynamic perspective.

Low dimensional structures, including bulk crystals, thin films, nanowires and nanotubes, have received remarkable attention due to their novel functionality and potential applications in various areas of optics, electronics, photonics, and sensing devices and photovoltaic field. Recently, remarkable progress and modification have been achieved in the synthesis process of crystalline material by vapor transport technique. In this review, we introduce an improved concept of the closed tube Chemical Vapor Transport (CVT) technique for the single crystal growth of ZrSTe, TiSTe and TiSeTe. A modified reverse temperature profile has reported the growth of ZrSTe, TiSTe and TiSeTe results show the good crystalline quality of synthesized materials. The single-crystal X-ray diffraction data reveals all three samples have trigonal unit cell structure with a space group of P31. The Semiconducting behavior of grown crystals of ZrSTe, TiSTe and TiSeTe was verified by two probe resistivity measurements, Hall Effect measurements and optical absorption at room temperature in the spectral range of 200 nm - 2200 nm. In this review, we highlight the recent progress in the transition of metal chalcogenides for their advanced application in solar energy conversion, thin-film electronics, optoelectronic devices and quantum communication devices. Moreover, different experimental challenges within the described growth technique are probed. Additionally, a survey was done for the possible enhancement of Transition Metal Chalcogenide (TMC) crystalline materials grown by the Chemical Vapor Transport technique based on various growth parameters.