Progress in Crystal Growth and Characterization of Materials最新文献

In this paper the results of structural analysis of the SnO₂ and In₂O₃ films deposited by spray pyrolysis are presented. The main goals of this analysis are summarizing the results obtained in this field, highlighting a correlation between parameters of film deposition and the material structure and formulating some general regularities, typical for metal oxides. Peculiarities and mechanisms of pyrosol deposition as well as advantages and disadvantages of this technology for deposition of the films with required parameters were also discussed. It is shown that this technology has great potential for controlling structural parameters of metal oxides such as thickness, the grain size, texturing, roughness, the grain faceting and the porosity.

The goal of this article is to provide an overview of the state of knowledge regarding the Atomic Layer Deposition (ALD) of metal oxides on III–V semiconductor surfaces. An introduction to ALD, the band structure, various defects present on the III–V surface and how they relate to Fermi level pinning are discussed. Surface passivation approaches are examined in detail in conjunction with experimental and computational results. The “interface clean-up” reaction that leads to the formation of a sharp gate oxide/semiconductor interface is related to the surface chemistry and the transport of the surface oxides through the growing dielectric film. Finally, the deposition of metal oxides on semiconductors is discussed in the context of interface quality and some examples of devices using III–V channels and ALD metal oxides are given.

A description is given of the traveling solvent technique, which has been used for the crystal growth of both congruently and incongruently melting materials of many classes of intermetallic, chalcogenide, semiconductor and oxide materials. The use of a solvent, growth at lower temperatures and the zoning process, that are inherent ingredients of the method, can help to grow large, high structural quality, high purity crystals. In order to optimize this process, careful control of the various growth variables is imperative; however, this can be difficult to achieve due to the large number of independent experimental parameters that can be grouped under the broad headings ‘growth conditions’, ‘characteristics of the material being grown’, and ‘experimental configuration, setup and design’. This review attempts to describe the principles behind the traveling solvent technique and the various experimental variables. Guidelines are detailed to provide the information necessary to allow closer control of the crystal growth process through a systematic approach. Comparison is made between the traveling solvent technique and other crystal growth methods, in particular the more conventional stationary flux method. The use of optical heating is described in detail and successful traveling solvent growth by optical heating is reported for the first time for crystals of Tl₅Te₃, Cd₃As₂, and FeSc₂S₄ (using Te, Cd and FeS fluxes, respectively).

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have received significant attention recently due to their unique properties such as a transition from indirect to direct band gap when thinned down to a monolayer and also valley-dependent photoluminescence. In addition, being a semiconductor with considerable mobility, it has been touted as a candidate in next generation electronics. However, a major hurdle to its implementation is the difficulty in producing large areas of these 2D TMDCs with well-defined thicknesses. In this review, we will first introduce the basic properties as well as the various synthesis methods of 2D TMDCs. Focus will be placed on recent advances in chemical vapor deposition (CVD) growth as they currently yield the largest areas. Obstacles present in CVD growth will be presented and existing solutions to them will be discussed in tandem with current characterization methods for evaluation of crystal quality. Through our presentation on the latest approaches to issues in CVD growth, we hope to present the readers a perspective on recent developments as well as providing an outlook on the future of CVD growth of TMDCs.

Aqueous–solid solution (AQ-SS) processes have garnered increasing attention from geochemists and environmental engineers because they play major roles in the fate and transport of elements in Earth surface environments. The reasons for this interest include: (i) the primary crystallization of minerals from multicomponent aqueous solutions leads to the formation of solid solutions in which different ions are substituted for one another in equivalent structural positions; (ii) the interaction between pre-existing minerals and water frequently yields surface precipitation and dissolution–recrystallization processes in which such substituting ions redistribute to adapt to new physicochemical conditions; (iii) the concentrations of specific minor elements in biogenic and abiogenic minerals have been shown to correlate with various parameters characterizing the growth environment (temperature, pH, nutrient levels, salinity, etc.) and the corresponding compositional signatures can be powerful tools in reconstructing the past from the sedimentary record; (iv) the aqueous concentration of heavy metals and other harmful ions can be significantly reduced by their incorporation into the structure of suitable host minerals and as such a ‘reduction of solubility’ can be exploited as a remediation strategy or used to design engineered barriers for the retention of metals, radionuclides, and other industrially generated inorganic wastes. In this review, the thermodynamics driving of AQ-SS processes is presented using examples of environmentally-relevant systems. The reaction pathways in AQ-SS processes depend not only on thermodynamic factors but also on kinetic and mechanistic effects, which operate at different scales in space and time. Examples of such effects include non-equilibrium ion partitioning, surface passivation, and compositional (sectorial, concentric, oscillatory) zoning. Finally, we discuss the contribution of both state-of-the-art characterization techniques and molecular simulation methods for the development of predictive models.

This article is intended to combine literature on cocrystallization – a tool for enhancing the solubility and for improving the physicochemical properties of an API (an API is the molecule which is responsible for providing the therapeutic effect) with special emphasis on the mechanism responsible for the same. The pharmaceutical industries are witnessing a developing crisis in the process of drug development due to the increasing cost of their R&D departments, the failure of some blockbuster drug candidates exhibiting poor aqueous solubility and the unavailability of newer molecules because of patent limitations. Cocrystallization is an emerging approach to improve solubility, dissolution profile, bioavailability, and other physicochemical and mechanical properties of an API. A pharmaceutical cocrystal is now a new epitome which enables the use of a wide range of active pharmaceutical ingredients without the need to form or break the covalent bonds. The prime focus of this review article is the mechanism on how cocrystals have a solubility advantage over the amorphous form. This review also provides a brief introduction to the nature of cocrystals, their role, principles of crystal engineering and also highlights the nature of supramolecular synthons which are present in cocrystals.

This article combines two papers, “Nobel Lecture: Growth of GaN on sapphire via low-temperature deposited buffer layer and realization of p-type GaN by Mg doping followed by low-energy electron beam irradiation,” Rev. Mod. Phys., 87 (2015) 1133, and “MOCVD of nitrides,” Handbook of Crystal Growth Second Edition, Volume III, Part A, Chapter 16, Elsevier, 683–704, 2015. For more detailed information, please read the two original papers.

Sixty-five years have passed since Burton, Cabrera and Frank (BCF) published the seminal paper (W. K. Burton, N. Cabrera and F. C. Frank, Phil. Trans. Royal Soc. London, 243 (1951), 299). Since then, the paper provided us the basic scheme of growth of crystals. In this lecture, the BCF theory is introduced for beginners as the basis of modern crystal growth study. The BCF theory explained the growth of facets with the help of screw dislocations. It introduced the concept of the roughening transition, which distinguishes the crucial difference of lateral growth of facets and normal growth of round surfaces.

The principle of interferometers and its applicability to our research on crystal growth can be understood through assembling interferometers. In particular, practical skills such as techniques for assembling interferometers and selecting optical components, which are not covered by general textbooks, can be learned.