Preferentially oriented vanadium nitride films deposited by magnetron sputtering

Because of solid state lubricious properties of vanadium oxides, wear resistant coatings based on nitrides and carbides of that metal are still of interest for research teams. The aim of this report is to show phase composition evolution from metallic vanadium through intermediate phases up to δ-VN phase supersaturated with nitrogen in thin films deposited by reactive, pulsed magnetron sputtering from vanadium target. This analysis is completed by remarks on preferential orientation, lattice constant and crystallite size. Presented work is a part of research on composite hard coatings for woodworking tools where vanadium nitrides and carbides are considered as a component reducing friction.     

Tuning the setup of sputter-coated multilayers in nanocluster-based signal-enhancing biochips for optimal performance in protein and DNA assays

In biochip development two issues are critical: stable and specific immobilization of the ligand and achievement of high signal-to-background ratio. In this work we have addressed these issues for the development of biochips, produced by sputtering multilayers of thin metal films, metal oxides, and metal nitrides (tens to hundreds of nanometers thick) onto glass wafers. Optimized surfaces have shown good results in genomic and proteomic experiments with biochips based on surface-enhanced fluorescence and absorption techniques.     

高压氢去除钒表面碳、氮、氧杂质的热力学分析

基于钒的相关相图,分析了钒表面钒的碳化物、氮化物和氧化物可能存在的形式。采用热力学方法计算了高温和高压条件下氢与钒碳化物、钒氮化物和钒氧化物的吉布斯自由能变,分析了高压氢去除上述杂质的可能性。计算结果表明,100MRa条件下钒表面的碳化物杂质转化为甲烷需要860K以上的温度;50MPa、低于1000K温度氢不能有效去除金属钒表面所有价态的钒氧化物;50MPa、298～1000K温度高压氢不能有效去除钒的氮化物。     

Thermal stability of refractory materials for high-temperature composite applications

A computational thermodynamic analysis of the stability of group IV, V, and VI transition metal borides, carbides, nitrides, and oxides is presented. The results of these computations can be employed to assess the stability and decomposition of these materials at high temperatures under different ambient conditions. The thermodynamic stabilities of group IV, V, and VI compounds increase with atomic number of the metal in the same group and decrease with atomic number in the same period. Based on the equilibrium computations of the decomposition reactions considered, V₃B₄, HfC, HfN and Ti₃O₅ are the most stable compounds in each class. In general, the refractory oxides are the most stable compounds followed by the borides, carbides and nitrides.     

Deposition processes for films and coatings

Deposition of films and coatings on different substrates is carried out mainly by using physical and chemical vapour deposition (CVD). Various films and coatings of metals, oxides, carbides, nitrides, suicides, borides, etc., are successfully deposited by the CVD process. An update on the deposition process and its applications is discussed in this paper.     

Microstructure trends in metal(aluminum,copper, indium,lead, tin)-metal oxide thin films prepared by reactive ion beam sputter deposition

Transmission electron microscopy has been used to study the microstructural trends of thin film composites prepared by sputtering of a metal (aluminum, copper, indium, lead or tin) target with argon ions in the presence of a reactive gas (oxygen). Results of these studies reveal that there is a general progression in the metal component microstructure which correlates with an increasing metal oxide component in the films and can be classified as belonging to an agglomerated-columnar-granular-amorphous sequence. These structural trends and the concomitant effect on film properties, such as resistivity, adhesion and mechanical stability, are a direct consequence of the metal-metal oxide interaction and the inhibiting effect which the native metal oxides have on metal atom diffusion during film formation.     

Electrical properties of high-temperature oxides,borides, carbides,and nitrides

High-temperature materials including oxides, borides, carbides, and nitrides encompass all types of conductors: metallic, semiconducting, and ionic. Their electrical conductivities are generally very sensitive to impurities regardless of the type of conductor. For large band-gap materials, which includes most of the oxides, the conductivities at low temperatures are frequently dominated by impurities or dopants, and intrinsic conduction only becomes significant above a temperature which depends largely on the level of dopant, the band gap and the defect structure of the base material. The borides, carbides, and nitrides of transition metals are metallic conductors with conductivities and temperature coefficients of resistivity comparable to that of their parent metals.     

New high-temperature materials and methods of investigating their thermophysical properties at temperatures up to 3500° C

Summary To summarize, we may conclude that the various new high-temperature materials such as refractory metals and their alloys, metal borides, carbides, nitrides, and silicides, oxides, refractory coatings, and heat shields, can be studied by the methods of high-temperature thermophysics.     

Synthesis of crystalline metal nitride and metal carbide nanostructures by sol–gel chemistry

Attention toward nanosized metal nitrides and carbides is rapidly increasing thanks to their chemical characteristics that make them as valid and sustainable alternatives to noble metals in catalysis and to air-sensitive metals or oxides for applications under harsh conditions. They are mostly used as bulk phase or micron sized powders, due to an intrinsic difficulty to synthesize them as nanoparticles in a systematic and scalable fashion. However, nanosized metal nitrides and carbides could exhibit improved performances, e.g. in catalysis due to a higher surface area, and can be shaped more easily than corresponding larger grains for further specific applications. Recently, sol–gel chemistry has closed this gap and now enables the simple, cheap, and sustainable production of metal nitride and carbide nanoparticles.In the present review we give an overview on recent sol–gel based pathways for the synthesis of metal nitride and carbide nanoparticles, believing that a better knowledge of the potentialities of these still hardly touched materials stimulates research interest and applications.     

Reaction between permalloy and several thin metal films

To develop the electrode materials for thin permalloy film devices, the reactions between the permalloy Ni-19%Fe and several metal films were investigated. From the results of the annealing behaviour for thin bilayer films including the permalloy, it was clarified that aluminium, copper, chromium and gold films react with the permalloy below 250–350°C. However, molybdenum and tantalum do not react up to 400°C. Therefore it is considered that molybdenum and tantalum are good electrode materials for thin permalloy film devices.     

超级电容器中的二维材料

以石墨烯为代表的具有层状结构的二维材料因具有大比表面积等特性成为超级电容器电极材料的热门候选。文章着眼于针对诸如石墨烯、过渡金属二硫族化合物、过渡金属碳/氮化物、层状过渡金属氧化物/氢氧化物等二维材料在超级电容器领域应用的研究,尝试总结了其制备方法、产物形貌特征以及作为电极的性能等,并对这一领域的未来发展和面临的挑战提出了看法与预测。     

Analysis of thin films arising from electron-, ion- and photon-beam-induced decomposition of Cr(CO)6 and Al(CH3)3

Thin films derived from ion and/or electron beam irradiation of condensed chromium hexacarbonyl (Cr(CO)₆) and trimethylaluminum (Al(CH₃)₃) and from laser-induced pyrolytic decomposition of Al(CH₃)₃ are analyzed using X-ray photoelectron spectroscopy. In all cases dissociation of the metal—carbon bonds may be achieved. Deposits of metallic aluminum overcoated with oxide were obtained from laser-induced pyrolysis, whereas oxides and carbides rather than metals usually result from the processing of the condensed molecular films by electron or ion beams. Modification to the sample composition as a function of electron, ion and photon beam dosage is discussed.     

超级电容器中的二维材料

以石墨烯为代表的具有层状结构的二维材料因具有大比表面积等特性成为超级电容器电极材料的热门候选.文章着眼于针对诸如石墨烯、过渡金属二硫族化合物、过渡金属碳/氮化物、层状过渡金属氧化物/氢氧化物等二维材料在超级电容器领域应用的研究,尝试总结了其制备方法、产物形貌特征以及作为电极的性能等,并对这一领域的未来发展和面临的挑战提出了看法与预测.     

Materials for supercapacitors: When Li-ion battery power is not enough

Supercapacitors, also known as electrochemical capacitors, have witnessed a fast evolution in the recent years, but challenges remain. This review covers the fundamentals and state-of-the-art developments of supercapacitors. Conventional and novel electrode materials, including high surface area porous carbons for electrical double layer capacitors (EDLCs) and transition metal oxides, carbides, nitrides and their various nanocomposites for pseudocapacitors – are described. Latest characterization techniques help to better understand the charge storage mechanisms in such supercapacitors and recognize their current limitations, while recently proposed synthesis approaches enable various breakthroughs in this field.     

Particulate reinforced metal matrix composites — a review

The physical and mechanical properties that can be obtained with metal matrix composites (MMCs) have made them attractive candidate materials for aerospace, automotive and numerous other applications. More recently, particulate reinforced MMCs have attracted considerable attention as a result of their relatively low costs and characteristic isotropic properties. Reinforcement materials include carbides, nitrides and oxides. In an effort to optimize the structure and properties of particulate reinforced MMCs various processing techniques have evolved over the last 20 years. The processing methods utilized to manufacture particulate reinforced MMCs can be grouped depending on the temperature of the metallic matrix during processing. Accordingly, the processes can be classified into three categories: (a) liquid phase processes, (b) solid state processes, and (c) two phase (solid-liquid) processes. Regarding physical properties, strengthening in metal matrix composites has been related to dislocations of a very high density in the matrix originating from differential thermal contraction, geometrical constraints and plastic deformation during processing.     

Diffusion barriers in thin films

Some of the conditions which thin film diffusion barriers should satisfy are enumerated. Various ways to try to meet these conditions are illustrated by means of examples. It is shown that metal films chosen for their mutual immiscibility with the adjoining metals (passive barriers) usually fail as barriers (i.e. are non-barriers) because extended structural defects in the metal film constitute fast diffusion paths. Single-crystal barriers of such metals are effective but not practical. Barriers which are thermodynamically partially stable (partially stable barriers) and those which are fully stable (stable barriers) are discussed. Metal compounds of particular interest for such barriers are suggested. The concept of the sacrificial barrier, which is based on an irreversible loss of barrier material by interfacial reactions with the adjoining metals, is introduced and successful applications are presented. The stabilizing effect of impurities on an otherwise unstable barrier (stuffed barriers), the importance of mechanical stress and the critical influence of the fabrication process of a thin film barrier on its actual performance are described by practical examples. Values of the electrical resistivity for borides, carbides, nitrides and silicides of the early transition metals and values of the coefficient of linear thermal expansion of silicides are compiled for reference purposes.     

Improved adhesion of ultra-hard carbon films on cobalt–chromium orthopaedic implant alloy

While interfacial graphite formation and subsequent poor film adhesion is commonly reported for chemical vapor deposited hard carbon films on cobalt-based materials, we find the presence of O₂ in the feedgas mixture to be useful in achieving adhesion on a CoCrMo alloy. Nucleation studies of surface structure before formation of fully coalesced hard carbon films reveal that O₂ feedgas helps mask the catalytic effect of cobalt with carbon through early formation of chromium oxides and carbides. The chromium oxides, in particular, act as a diffusion barrier to cobalt, minimizing its migration to the surface where it would otherwise interact deleteriously with carbon to form graphite. When O₂ is not used, graphitic soot forms and films delaminate readily upon cooling to room temperature. Continuous 1 μm-thick nanostructured carbon films grown with O₂ remain adhered with measured hardness of 60 GPa and show stable, non-catastrophic circumferential micro-cracks near the edges of indent craters made using Rockwell indentation.     

Nanocrystalline high melting point compound-based materials

The different preparation methods of ultrafine powders of high melting point compounds (carbides, borides, nitrides, and oxides with melting temperatures higher than 2000C) are reviewed. Some properties of these powders are discussed and compared. The consolidation behaviour of these compounds in the nanocrystalline (nc) state is described in detail. Compaction by hot pressing, including high pressures and high temperatures, sintering, and high-energy consolidation methods, is analysed. The microstructure, recrystallization, mechanical and physical properties of nc-carbides, nitrides, and oxides are characterized. Special attention is focused on relationships between structure and properties.     

Emerging 2D metal oxides and their applications

In the past decade, several different classes of two-dimensional (2D) materials beyond graphene such as layered polymorphs of group V elements (phophorene, arsenene), Metalenes (gallenene, stanene etc.), Transition Metal–Dichalcogenides (TMDs), group III monochalcogenides, transition metal carbides as well as nitrides have been thoroughly explored. These atomically thin materials have gathered significant focus due to their unique electronic, optical, and magnetic properties, which are seldom found in their bulk counterparts due to the high surface to volume ratios and quantum confined electronic structure. These properties have led to excitement in the research community due to their potential applications in various fields of optoelectronics, energy harvesting and storage, sensing, electronics, magneto-electronics, and thermo-electronic applications. However, there is another emerging class of layered oxide 2D materials, which has been sporadically explored and lacks a systematic compilation of the made progress, potential benefits and research opportunities that may lie ahead. This specific review provides a thorough and systematic summary of research carried out on layered 2D oxides both from an experimental and theoretical perspective. Due to ultra-thin nature of the 2D metal oxides, a majority of the atoms are accessible to the surfaces, which induces new properties and applications in comparison to traditional bulk oxides. We discuss several different classes of metal oxides in their 2D forms such as MO, MO_x, M_xO_y (where M stands for metals; x and y possible oxidation states) as well as Perovskite type oxides in this review specifically focusing on optoelectronics, sensing and electrochemical storage applications. We further make critical comparisons with bulk metal oxides, and elaborate the specific advantages of 2D metal oxides as compared to their bulk counterparts in respective applications. Finally, we conclude by providing a critical assessment and outlook of technical challenges and research opportunities for future development of layered 2D oxides.     

Effect of deposition process parameters on resistivity of metal and alloy films deposited using anodic vacuum arc technique

Thin solid films of copper, aluminum and nichrome have been deposited on glass substrates with thickness ranging from 20 nm to 200 nm, using the anodic vacuum arc deposition technique. Electrical resistivity and average grain size of deposited thin films have been measured and their dependence on the deposition process parameters has been investigated. Thickness dependence of resistivity has also been compared with numerically generated results using Fuchs-Sondheimer theory and Mayadas-Shatzkes theory which has been found to be in good agreement for film thickness greater than 80 nm. The resistivity values of Cu, Al and NiCr has been found to take a minimum value (approaching that of corresponding bulk material) of 80 A arc current and a substrate bias of around − 50 V.