Progress in Crystal Growth and Characterization of Materials最新文献

The integration of III–V semiconductors with Si has been pursued for more than 25 years since it is strongly desired in various high-efficiency applications ranging from microelectronics to energy conversion. In the last decade, there have been tremendous advances in Si preparation in hydrogen-based metalorganic vapor phase epitaxy (MOVPE) environment, III–V nucleation and subsequent heteroepitaxial layer growth. Simultaneously, MOVPE itself took off in its triumphal course in solid state lighting production demonstrating its power as industrially relevant growth technique. Here, we review the recent progress in MOVPE growth of III–V-on-silicon heterostructures, preparation of the involved interfaces and fabrication of devices structures. We focus on a broad range of in situ, in system and ex situ characterization techniques. We highlight important contributions of density functional theory and kinetic growth simulations to a deeper understanding of growth phenomena and support of the experimental analysis. Besides new device concepts for planar heterostructures and the specific challenges of (001) interfaces, we also cover nano-dimensioned III–V structures, which are preferentially prepared on (111) surfaces and which emerged as veritable candidates for future optoelectronic devices.

Second half of the XX century was marked by a rapid development of sapphire shaped crystal growth technologies, driven by the demands for fast, low-cost, and technologically reliable methods of producing sapphire crystals of complex shape. Numerous techniques of shaped crystal growth from a melt have been proposed relying on the Stepanov concept of crystal shaping. In this review, we briefly describe the development of growth techniques, with a strong emphasize on those that yield sapphire crystals featuring high volumetric and surface quality. A favorable combination of physical properties of sapphire (superior hardness and tensile strength, impressive thermal conductivity and chemical inertness, high melting point and thermal shock resistance, transparency to electromagnetic waves in a wide spectral range) with advantages of shaped crystal growth techniques (primarily, an ability to produce sapphire crystals with a complex geometry of cross-section, along with high volumetric and surface quality) allows fabricating various instruments for waveguiding, sensing, and exposure technologies. We discuss recent developments of high-tech instruments, which are based on sapphire shaped crystals and vigorously employed in biomedical and material sciences, optics and photonics, nuclear physics and plasma sciences.

Recent progress in ammonothermal technology of bulk GaN growth in basic environment is presented and discussed in this paper. This method enables growth of two-inch in diameter crystals of outstanding structural properties, with radius of curvature above tens of meters and low threading dislocation density of the order of 5 × 10⁴ cm⁻². Crystals with different types of conductivity, n-type with free electron concentration up to 10¹⁹ cm⁻³, p-type with free hole concentration of 10¹⁶ cm⁻³, and semi-insulating with resistivity exceeding 10¹¹ Ω cm, can be obtained. Ammonothermal GaN of various electrical properties is described in terms of point defects present in the material. Potential applications of high-quality GaN substrates are also briefly shown.

This review is an audit of various Carbon fibers (CF) surface modification techniques that have been attempted and which produced results with an enhancement in the interfacial characteristics of CFRP systems. An introduction to the CF surface morphology, various techniques of modifications, their results and challenges are discussed here. CFs are emerging as the most promising materials for designing many technologically significant materials for current and future generations. In order to extract all the physic-mechanical properties of CF, it is essential to modulate a suitable environment through which good interfacial relation is achieved between the CF and the matrix. The interface has the utmost significance in composites and hybrid materials since tension at the interface can result in a deterioration of the fundamental properties. This review is aimed to provide a detailed understanding of the CF structure, its possible ways of modification, and the influence of interfacial compatibility in physic-mechanical and tribological properties. Both physical and chemical modifications are illustrated with specific examples, in addition to the characterization methods. Overall, this article provides key information about the CF based composite fabrication and their many applications in aerospace and electronics- where light weight and excellent mechanical strength are required.

Solution combustion synthesis (SCS) is a worldwide used methodology for the preparation of inorganic ceramic and composite materials with controlled properties for a wide number of applications, from catalysis to photocatalysis and electrocatalysis, from heavy metal removal to sensoristics and electronics. The high versatility and efficiency of this technique have led to the introduction of many variants, which allowed important optimization to the prepared materials. Moreover, its ecofriendly nature encouraged further studies about the use of sustainable precursors for the preparation of nanomaterials for energy and environment, according to the concept of circular economy. On the other hand, the large variety of expressions to define SCS and the often-contradictory definitions of the SCS parameters witnessed a scarce consciousness of the potentiality of this methodology. In this review article, the most important findings about SCS and the selection criteria for its main parameters are critically reviewed, in order to give useful guidelines to those scientists who want to use this methodology for preparing materials with improved or new functional properties. This review aims as well (i) to bring more clarity in the SCS terminology (ii) to increase the awareness of the SCS as a convenient tool for the synthesis of materials and (iii) to propose a new perspective in the SCS, with special attention to the use of ecofriendly procedures. Part of the review is also dedicated to precautions and limitations of this powerful methodology.

The electrical, magnetic, and structural features of bismuth manganite (BM), e.g., BiMnO₃, and bismuth ferrite (BF), e.g., BiFeO₃, are reviewed. Induced multiferroicity and enhanced magnetoelectric coupling are required for various modern device applications. BM and BF were synthesized using standard high-temperature sintering and processes such as sol–gel, hydrothermal, or wet chemical methods combined with annealing. The size and morphology of the nanoscale particles were controlled, although they were usually inhomogeneous. BF exhibits structurally stable antiferromagnetic (AFM) and ferroelectric (FE) phases in wide temperature ranges. Ferromagnetic (FM) order was induced in a thick shell around the AFM core of the nanoscale BF particles, which was attributed to a size effect related to surface strains and disorder. BM exhibited both structurally stable and unstable phases. The BiMnO₃, Bi₁₂MnO₂₀, and BiMn₂O₅ structures are nonferroelectric. The perovskite BiMnO₃ form was synthesized under high hydrostatic pressure. FM order occurs in BM at low temperatures. Bi(MnFe)O₃ solid solution samples exhibited competition between AFM and FM ordering. Doping can decrease the content of unavoidable secondary phases. Doping in the Bi ion sublattice can stabilize the crystal lattice owing to local strains caused by the difference in ionic radius between Bi and the dopant. Doping in the Fe and Mn sublattices affects the electrical features. The main achievement of substitution with tetra- and pentavalent ions is compensation of the oxygen vacancies. In turn, leakage current suppression enables switching of FE domains and polarization of the samples. A significant enhancement of magnetoelectric coupling was observed in composites formed from BF and other FE materials. The leakage currents can be diminished when an insulator polymer matrix blocks percolation. The potential applicability is related to enhanced magnetoelectric coupling. The constructed devices meet the size effect limitations for FE and FM ordering. Resistive switching suggests possible use in nonvolatile memories and gaseous sensors. The sensors can be used for hydrophones and for photovoltaic and photoluminescence applications, and they can be constructed from multiphase materials. Bulk multiferroic solid solutions, composites, and nanoheterostructures have already been tested for use in sensors, transducers, and read/write devices for technical purposes.

Monolithic integration of III-V on silicon has been a scientifically appealing concept for decades. Notable progress has recently been made in this research area, fueled by significant interests of the electronics industry in high-mobility channel transistors and the booming development of silicon photonics technology. In this review article, we outline the fundamental roadblocks for the epitaxial growth of highly mismatched III-V materials, including arsenides, phosphides, and antimonides, on (001) oriented silicon substrates. Advances in hetero-epitaxy and selective-area hetero-epitaxy from micro to nano length scales are discussed. Opportunities in emerging electronics and integrated photonics are also presented.

In the great adventure of two-dimensional (2D) materials, the characterization techniques are the lighthouse to guide the investigators across heavy mist and submerged reef. In this review, we highlight the recent achievements in the characterization of the 2D materials. Firstly, the methods to identify the fundamental properties of the 2D materials are introduced. Then, the specific characterization techniques for analyzing electric, optical and chemical properties are summarized with regards to their corresponding fields of applications. It should also be noted that a big challenge remains in the characterizations of the 2D materials in the hybrid or composite and wide acceptance of the characterization standards need to be established to further promote the industrialization of 2D materials in the near future.

The synthesis of crystals through biomineralization is a process of protection and support preserved in animals, protists, moneras, plants and fungi. The genome of every species has evolved to preserve and/or modify the formation of one or another type of crystal, which may be of the organic or inorganic type. The most common inorganic crystals identified in organisms include calcium carbonate (CaCO₃), calcium phosphate (CaP), calcium oxalate (CaOx), magnetite or greigite, and sulfides of cadmium (CdS), mercury (HgS) and lead (PbS). Organic crystals are of the protein or ice type. The formation of both types of crystals requires biomolecules such as proteins. This paper reviews the proteins involved in the synthesis of different crystals in distinct biological systems, in order to understand how each organism has adapted its genome to preserve essential mechanisms such as biomineralization, which has enabled them to survive in a changing environment for millions of years.