Polycrystalline Diamond Characterisations for High End Technologies

Characterisations of polycrystalline diamond (PCD) coatings have routinely been done over the past three decades of diamond research, but there is less number of reports on some of its very unique properties. For example, diamond is the hardest known material and, in probing such hard surfaces with any indenter tip, it may lead to damage of the instrument. Due to such chances of experimental accidents, researchers have performed very few attempts in evaluating the mechanical properties of PCDs. In the present work, some of these very special properties of diamond that are less reported in the literature are being re-investigated. PCDs were characterised by photoluminescence (PL), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscope (TEM), and X-ray diffraction (XRD) techniques. The diamond surface was also polished to bring the as-grown micron level of surface roughness (detrimental for wear application) down to few hundreds of nanometer. The tribological properties of such polished and smooth surfaces were found to be appropriate for wear protective coating application. This chapter revisits some of the unreported issues in the synthesis and characterisation of PCD coatings grown on Si wafer by the innovative 915 MHz microwave plasma chemical vapour deposition (MPCVD) technique

Microwave Plasma CVD Grown Single Crystal Diamonds - A Review

Diamond offers a range of unique properties, including wide band of optical transmission, highest thermal conductivity, stiffness, wear resistance and superior electronic properties. Such high-end properties are not found in any other material, so theoretically it can be used in many technological applications. But the shortcoming has been the synthesis of the diamond material in the laboratory for any meaningful use. Although microwave plasma chemical vapour deposited (MPCVD) has been in practice since 1980s for the diamond growth but it is in the past 7-8 years that its potential has been realised by the industry due to capability of MPCVD to deposit diamond, pure and fast, for commercial uses. There are many CVD techniques for growing diamond but among them MPCVD can only make single crystal diamond (SCD) effectively. SCD grown by MPCVD is also superior to other forms of diamond produced in the laboratory. For example, SCD is necessary for the best electronic properties - often outperforming the polycrystalline diamond (PCD), the high pressure high temperature (HPHT) diamond and the natural diamond. In many applications the short lateral dimensions of the lab-grown diamond available is a substantial limitation. Polycrystalline CVD diamond layers grown by hot filament CVD solved this problem of large area growth, but the presence of grain boundaries are not appropriate for many uses. On the other hand, there is still limitation in the area over which SCDs are grown by MPCVD, only upto 10-15 mm lateral sizes could have been achieved so far, while there are recipes which rapidly grow several mm thick bulk SCDs. This lateral size limitation of SCDs is primarily because of the small seed substrate dimension. Although natural and HPHT diamonds may not be suitable for the intended application, still they are routinely used as substrates on which SCD is deposited. But the problem lies in the availability of large area natural SCD seeds which are extremely rare and expensive. Moreover, large diamond substrate plates suitable for CVD diamond growth have not been demonstrated by HPHT because of the associated high economic risk in their fabrication and use. Other than lateral dimension, purity of SCD is also very important for technological use. Natural diamond is often strained and defective, and this causes twins and other problems in the CVD overgrowth or fracture during synthesis. In addition, dislocations which are prevalent in the natural diamond substrate are replicated in the CVD layer, also degrading its electronic properties. HPHT synthetic diamond is also limited in size, and generally is of poorer quality in the larger stones, with inclusions being a major problem. There will be much research interest in the next 10 years for the MPCVD growth of SCD. Purer and bigger SCDs will be tried to grow with faster and reproducible MPCVD recipes. Here the MPCVD growth of SCD is being reviewed keeping in mind its huge technological significance in the next decades or so. Discoveries of the commercial productions of silicon, steel, cement different materials have built modern societies but higher scales will be achieved with the advent of lab-grown diamond

Characteristics of CVD Grown Diamond Films on Langasite Substrates

Surface acoustic wave (SAW) devices consist of a piezoelectric substrate with interdigitated (IDT) electrodes. These devices can be used to fabricate wireless and passive sensors that can be mounted in remote and/or inaccessible places. If encapsulated with CVD diamond, the SAW devices can be made to operate under extremely hostile conditions. The piezoelectric layer (AlN, ZnO etc.) deposited on the diamond or an inverse system can increase the frequency of the SAW device. Most piezoelectric materials (such as quartz) show phase transition temperatures below diamond deposition temperature (650º-1100ºC), preventing their use as a substrate for diamond growth. Langasite La3Ga5SiO14 (LGS) is recently fabricated piezoelectric material that can withstand high temperatures without being deteriorated. LGS does not have phase transitions up to its melting point of 1470°C.Here we report the deposition of diamond films by microwave plasma CVD in methane-hydrogen gas mixtures on polished and rough surfaces of the LGS substrates seeded with nanodiamonds. No buffer layer between the substrate and the coating had been used. The effect of substrate pretreatment (PT) was also investigated on the growth behaviour of diamond films on LGS. The resulting films are characterised by Raman spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS). The effect of substrate roughness on the growth behaviour was found to favour bigger grain sizes on the unpolished substrates. Whereas, the effect of substrate pretreatment (PT) was found to produce unique microstructural features with better polycrystalline diamond (PCD) quality than on the substrates without PT. Raman signals confirm the deposition of PCD in all the cases but the X-ray results interestingly show new phase formation of hcp and rhombohedral diamond lattice structures under CVD growth environment

Deposition of diamond films on single crystalline silicon carbide substrates

Silicon carbide (SiC) is a wide band gap material that is slowly but steadily asserting itself as a reliable alternative to silicon (Si) for high temperature electronics applications, in particular for the electrical vehicles industry. The passivation of SiC devices with diamond films is expected to decrease leakage currents and avoid premature breakdown of the devices, leading to more efficient devices. However, for an efficient passivation the interface between both materials needs to be virtually void free and high quality diamond films are required from the first stages of growth. In order to evaluate the impact of the deposition and seeding parameters in the properties of the deposits, diamond films were deposited on SiC substrates by hot filament chemical vapor deposition (HFCVD). Before the seeding step the substrates were exposed to diamond growth conditions (pre-treatment PT) and seeding was performed with a solution of detonation nanodiamond (DND) particles and with 6–12 and 40–60 μm grit. Diamond films were then grown at different temperatures and with different methane concentrations and the deposits were observed in a scanning electron microscope (SEM); their quality was assessed with Raman spectroscopy.publishe

Deposition and characterization of diamond-like nanocomposite coatings grown by plasma enhanced chemical vapour deposition over different substrate materials

Diamond-like nanocomposite (DLN) coatings have been deposited over different substrates used for biomedical applications by plasma-enhanced chemical vapour deposition (PECVD). DLN has an interconnecting network of amorphous hydrogenated carbon and quartz-like oxygenated silicon. Raman spectroscopy, Fourier transform-infra red (FT-IR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been used for structural characterization. Typical DLN growth rate is about 1 m/h, measured by stylus profilometer. Due to the presence of quartz-like Si:O in the structure, it is found to have very good adhesive property with all the substrates. The adhesion strength found to be as high as 0 center dot 6 N on SS 316 L steel substrates by scratch testing method. The Young's modulus and hardness have found to be 132 GPa and 14 center dot 4 GPa, respectively. DLN coatings have wear factor in the order of 1 x 10 (-aEuro parts per thousand 7) mm (3) /N-m. This coating has found to be compatible with all important biomedical substrate materials and has successfully been deposited over Co-Cr alloy based knee implant of complex shape

The future of the technology-based manufacturing in the European Union

The manufacturing industry tries to innovate always to cater to customer-oriented products. The digitization of manufacturing is revolutionizing the future of this industry. The Industrial Internet of Things (IIoT) is bringing down the labor cost, reducing the machine downtime, and overall increasing the production speed. A new technological trend like Machine Learning (ML) is a subset of Artificial Intelligence (AI) that uses computer algorithms based on available data and can improve or decide further, automatically, based on experience, without the need for prior programming commands. ML can improve daily processes for identifying bottlenecks, developing products, controlling quality, providing security to the industry, and using AI robotics in place of humans. On one hand, technologies like ML, AI, IIoT, new materials, photonics, and rapid prototyping are driving the manufacturing sector in adopting a future version of Industry 4.0, and on the other hand, the European Commission (EC) has defined a roadmap until 2050 or more, in achieving the sustainable goal of carbon-neutrality and complete digitalization with resilience across the European continent. However, it is challenging to match the planned and actual roadmaps to the future of the technology-based manufacturing industry. There are uncertainties about how the future will be shaped by technologies in the EU manufacturing industry, in the changing political, environmental and social world environment. Recognizing these difficulties, the current article consults the available literature on this topic to determine the factors that will characterize the future of the manufacturing industry across EU countries. The relevant information about the EU manufacturing sectors has first been collected from various sources like Eurostat data, the EC policy documents, manufacturing company's annual reports, research reviews, journal articles, EU Industry Days annual event, etc. Then the collected data were analyzed to gain insight into the future of the technology-based EU manufacturing industry in the context of the European Commission's outlined policies. Variable factors from different manufacturing sectors are presented from different EU member states and scenario analysis was used for understanding the possible future. It is concluded that the future does not lie in adapting to the changing environment but in creating the future by EU companies themselves - revolution must be met by revolution. Their early experiences and path dependency can be seen as stubbornness, which may act as formidable barriers to building new capabilities. Therefore, companies must step-wise integrate resources to create a new process, and new structure, with personnel motivation, that fits with the broader European context in the coming decades

An effort in planarising microwave plasma CVD grown polycrystalline diamond (PCD) coated 4 in. Si wafers

Large area CVD grown diamond coatings should have very smooth surface in many of its applications, like microwave power transmission windows etc. Combination of mechanical and chemical forces during polishing helps to achieve desired surface roughness of the polycrystalline diamond (PCD) coatings. Authors report the variation of pressure, slurry feeding rate, addition of chemicals and the time of polishing to observe the efficiency of chemo-mechanical polishing (CMP) technique in planarising CVD diamond material grown over 100 mm diameter silicon wafers. PCD were found to be polished by bringing down the as-grown surface roughness from 1.62 gm to 46 nm at some points on large areas. One coherence scanning interferometer was used to check the roughness at different stages of CMP. Raman spectroscopy was used to evaluate the polished PCD samples in terms of their quality, internal stress at different positions on the same wafer surface after CMP process. It was found that the well polished regions were of better quality than the less polished regions on the same wafer surface. But due to coating non-uniformity of the deposited PCD grown by microwave plasma CVD over large area, CMP could not produce uniform surface roughness over the entire 100 mm diameter wafer surface. We concluded that CMP could effectively but differentially polish large area PCD surfaces, and further process improvements were needed. (C) 2015 Elsevier Ltd. All rights reserved

CeO2@C derived from benzene carboxylate bridged metal-organic frameworks: ligand induced morphology evolution and influence on the electrochemical properties as a lithium-ion battery anode

We report herein a facile metal-organic framework (MOF) derived route for the synthesis of carbon embedded CeO2 (CeO2@C) with a pre-designed shape-specific morphology by varying the organic linker and by using PVP as the structure directing agent. It is found that the general morphological features of the parent MOF are mimicked by the derived oxide. Four different linkers have been used to prepare CeO2@C particles with three different shapes-spherical, bar-shaped and thin plate-like. A probable formation mechanism is discussed based on metal-ligand coordination. Influence of the morphology on the electrochemical properties as a lithium-ion battery (LIB) anode has been studied in coin cells vs. Li/Li+. The spherically shaped CeO2@C-14 shows a superior performance with a maximum specific capacity of 715 mA h g(-1) at 0.05 mA cm(-2), good rate performance (413 mA h g(-1) at 0.5 mA cm(-2)) and cycling stability (similar to 94% capacity retention after 100 cycles). The present results demonstrate that the major limitations of metal oxide anodes-volume expansion during lithiation/delithiation, rate performance and capacity fading upon cycling-could be overcome to a great extent by adopting the two-way approach of morphology design through the MOF route and in situ embedded carbon matrix

Micrometer size grains of hot isostatically pressed alumina and its characterization

Alumina samples were prepared from two different particle size powders. Finer particle compacts when heated along with coarser particle compacts at same processing temperatures produce bigger grain microstructures due to higher grain growth. An unconventional method of etching by molten V(2)O(5) was adopted to look at the microstructure for accuracy in reported data. On an average starting with finer particles give microstructure with a grain size of 5.5 mu m and starting with coarser particles, give microstructure with 2.2 mu m average grain size. The flexural strength is around 400 MPa for alumina samples prepared from finer powder in comparison with about 550 MPa for alumina samples prepared from coarser powder. The Vickers hardness in 5.5 mu m grain microstructure is around 20 GPa in comparison to about 18 GPa in microstructure with smaller grains of 2.2 mu m size