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Large size single crystal diamond (SCD) wafer has been strongly desired for various of advanced applications, while two major potential approaches, including mosaic growth and heteroepitaxy based on chemical vapor deposition method, are both stuck with respective technical barriers. This paper reveals and summarizes the essential commonality of the two schemes, and denominates the concept of “coessential-connection” (CC) growth. Such generalized concept involved the nature of the single crystal and polycrystalline diamond film deposition with similar mechanism and processes. The principle of CC growth process with detailed classification was elaborated, and influence of nucleus size and orientation mismatch was clarified, which is regarded as the core problem of large area SCD film growth via coessential-connection process.

Diamond field-effect transistor (FET) has great application potential for high frequency and high power electronic devices. In this work, diamond FETs were fabricated on (0 0 1) single crystal diamond with homoepitaxial layer. The nitrogen impurity content in the homoepitaxial layer is greatly decreased as measured by the Raman and photoluminescence spectra. The diamond field effect transistor with 100 nm Al2O3 as gate dielectric shows ohomic contact resistance of 35 Ω . mm, maximum drain saturation current density of 500 mA/mm, and maximum transconductance of 20.1 mS/mm. Due to the high quality of Al2O3 gate dielectric and single crystal diamond substrate, the drain work voltage of −58 V is achieved for the diamond FETs. A continuous wave output power density of 4.2 W/mm at 2 GHz is obtained. The output power densities at 4 and 10 GHz are also improved and achieve 3.1 and 1.7 W/mm, respectively. This work shows the application potential of single crystal diamond for high frequency and high power electronic devices.

The dislocation identification method using X-ray topography by reflection mode geometry was applied to characterize IIa, Ib and highly B doped high pressure high temperature (HPHT) grown crystals. In both IIa and Ib crystals, dislocations are found to propagate in the <111> grown direction, with dominant vectors of [110] and [1-10], neither of which has no c-axis segment. For Ib crystal, many dislocations are also generated in the <112> and <121> directions, which are slightly tilted to <111>. It was confirmed that the dislocations in the same direction have the same Burgers vectors, but the dislocations are spread in broad area. A total of up to 20 HPHT crystals were measured and found to exhibit different dislocation distributions. This indicates an immature growth technique in terms of dislocation. Measurements of four chemical vapor deposition (CVD) substrates showed numerous dislocation bundles, making individual dislocation directions analysis impossible. CVD substrates suffer from an increase in dislocations due to CVD growth, resulting in poor diamond quality in terms of dislocation. XRT analysis on dislocations of epitaxial growth will be very important prior to CVD substrates analysis.

A GaN-on-diamond structure is the most promising candidate for improving the heat dissipation efficiency of GaN-based power devices. Room-temperature bonding of GaN and diamond is an efficient technique for fabricating this structure. However, it is extremely difficult to polish diamond to an average roughness (Ra) below 0.4 nm, especially for polycrystalline diamond. In this work, Room-temperature bonding of GaN and rough-surfaced diamond with a SiC layer was successfully achieved by a surface-activated bonding (SAB) method. The diamond surface’s initial Ra value was 0.768 nm, but after deposition of the SiC layer, the Ra decreased to 0.365 nm. The SiC layer formed at the as-bonded GaN/diamond interface was amorphous, with a thickness of about 7 nm. After annealing at 1000-°C, the amorphous SiC layer became polycrystalline, and its thickness increased to approximately 12 nm. These results indicate that the deposition of a SiC layer on diamond can efficiently lower the diamond surface’s roughness and thus facilitate room-temperature bonding.

In the future, electronic parts will penetrate everything, generating a new and fast-growing pollution problem. Future devices therefore need to be environmentally friendly with strong recycling options. A paradigm change in semiconductor technology is predicted based on applications of better suited materials which can fulfil these criteria. Carbon based materials and here especially diamond are promising candidates. Bulk and surface properties of diamond are introduced in combination with applications in power electronics, quantum technology, bio-and electrochemistry and MEMS. Large amounts of diamond seeds and wafers will be required to approach commercial markets. Their availability in combination with quality and size as well as required energies for production are introduced. The production of CVD diamond is currently about 100–250 times more intense with respect to energy than Silicon. A problem which is addressed by use of new solid-sates microwave sources. The definition of “green diamond” is given taking into account requirements with respect to energy and methane/hydrogen production. A brief discussion and comparison of diamond global markets and related potentials in comparison to SiC and GaN is given.

Diamond with an ultra-wide bandgap shows intrinsic performance that is extraordinarily superior to those of the currently available wide-bandgap semiconductors for deep-ultraviolet (DUV) photoelectronics and microelectromechanical systems (MEMS). The wide-bandgap energy of diamond offers the intrinsic advantage for solar-blind detection of DUV light. The recent progress in high-quality single-crystal diamond growth, doping, and devices design have led to the development of solar-blind DUV detectors satisfying the requirement of high Sensitivity, high Signal-to-Noise ratio, high spectral Selectivity, high Speed, and high Stability. On the other hand, the outstanding mechanical hardness, chemical inertness, and intrinsic low mechanical loss of diamond enable the development of MEMS sensors with boosted sensitivity and robustness. The micromachining technologies for diamond developed in these years have opened the avenue for the fabrication of high-quality single-crystal diamond mechanical resonators. In this review, we report on the recent progress in diamond DUV detectors and MEMS sensors, which includes the device principles, design, fabrication, micromachining of diamond, and devices physics. The potential applications of these sensors and a perspective are also described.

This review focuses on describing the fundamental/applied materials science and technological applications of a transformational multifunctional diamond-based material named ultranano­crytalline diamond (UNCDTM) in film form. The UNCDTM films are synthesized using microwave plasma chemical vapor deposition (MPCVD) and hot filament chemical vapor deposition (HFCVD), via patented Ar/CH4 gas flown into air evacuated chambers, using microwave power, or hot filaments’ surface, to crack CH4 molecules to generate C atoms and CHx (x = 1, 2, 3) species, which produce chemical reactions on substrates’ surfaces, producing diamond film with grain sizes in the range 3–5 nm (smallest grain size known today for any polycrystalline diamond film), providing the bases for the name UNCD. UNCD coatings exhibit a unique combination of properties, namely: (1) super high hardness and Young modulus, similar to the crystal gem of diamond; (2) lowest coefficient of friction compared to other diamond or diamond-like coatings; (3) no mechanical surface wear; (4) highest resistance to chemical attach by any corrosive fluid; (5) only diamond film exhibiting electrical conductivity via Nitrogen inserted in grain boundaries, binding to C atoms and providing electrons for electrical conduction, or B atoms substituting C atoms in the diamond lattice, providing electrons to the conduction band; and (6) best biocompatibility, since UNCD coatings are formed by C atoms (element of life in human DNA, cells/molecules). The UNCD films’ properties provide unique multifunctionalities, enabling new generations of industrial, electronic, high-tech, and implantable medical devices/prostheses, enabling substantial improvement in the way and quality of life of people worldwide.

It has been half of a century since the publication of the early reports about CVD diamond films in the world in the early 1970’s. The reports for meaningful laboratory growth of diamond films with much higher growth rate and higher quality could be found in the early 1980’s, under the so-called “Diamond Fever” initiated all over the world. In less than 10 years later, CVD diamond research had started in China as “863 Plan” (High Technology Research and Development Plan in China), a newly launched program in 1987. 35 years later, it is very interesting to explore what really happened to the CVD diamond in China. As a multi-functional material with a vast combination of extraordinary electrical, mechanical, thermal, optical, acoustic, and electro-chemistry properties, the CVD diamond has wide applications potentially in the field of multidiscipline high technologies. Therefore, this article aims to provide a general review on the CVD diamond by presenting a clearer picture about the history, the research status and its development, particularly the commercialization in China. Finally, the general trend in the near future is discussed.

Peculiarities of the processes of self-assembly of carbon under pressure up to 8 GPa and temperatures up to 1600°C in pure carbon, hydrocarbon, fluorocarbon, organometallic systems and binary mixtures of all-carbon, hydrocarbon, and fluorocarbon compounds have been revealed in the course of studies of pressure and temperature-induced transformations of different carbon-containing systems. It was shown that the character of the processes of self-assembly of carbon in different systems is controlled in the first place by the mobility of carbon atoms. The low diffusion mobility of carbon atoms in a condensed state at temperatures below 2000° C leads to the fact that in pure carbon systems studied on the examples of fullerite C60 and closed polyhedral carbon nanoparticles, carbon self-organization can occur only due to processes associated with small movements of carbon atoms that ensure the formation of intermolecular bonds in cases of polymerization of C60 or the restructuring of the internal structure of a polyhedral particle, strictly limited to the confines of a single nanoparticle. In the hydrocarbon and fluorocarbon systems, the character of transformation changes drastically due to formation of volatile low-molecular hydrocarbon and fluorocarbon fractions, which ensure a high gas-phase or fluid mobility to carbon atoms. Studies of pressure and temperature-induced transformations of different hydrocarbon, fluorocarbon compounds and their homogeneous binary mixtures revealed a clear synergistic effect of fluorine and hydrogen on processes of carbonization, graphitization, and formation of diamond in these systems in relation to industrially significant reduction of p,T parameters for formation of graphite, diamond and increase in the content of nanosize diamond fractions in the products of transformations of binary mixtures in comparison with pure hydrocarbon and fluorocarbon compounds. Discovery of this synergistic effect opens new opportunities for synthesis of high-purity and doped ultranano-, nano-, submicro-, and micronsized diamonds with the specific properties for different applications in quantum physics and biomedicine. Studies of particularities of self-assembly of carbon in processes of thermal transformations of ferrocene at high pressures demonstrated the possibility of preparation of iron carbide nanoparticles encapsulated into carbon shells, Fe7C3@C and Fe3C@C, considered as perspective magneto-controlled platforms for different biomedical nanocomplexes.

Carbon, the fourth most abundant element in the Universe, possesses numerous allotropes with diverse bonding character (sp1-, sp2- and sp3-hybridized bonds) and structural motif of the constituting atoms. In particular, the carbon materials with a fully or nearly 100% sp3-hybridized strong C-C bonds often lead to excellent mechanical properties, chemical stability, thermal and optical properties, such as crystalline diamond and diamond-like amorphous carbon (DLC). In this review, we systematically summarize the synthesis, microstructure, mechanical properties, thermal and optical properties of ultrahard carbon materials with current experimental results on nano-polycrystalline diamond (NPD), nanotwinned diamond (NTD), micro-grained polycrystalline diamond (MPD), and amorphous diamond/carbon. In addition, we discuss the difference of spectra of XRD, Raman and EELS between various nanocrystalline diamond powder and ultrahard carbon materials. Finally, we provide our insights into the future development and applications in the research of ultrahard carbon bulk materials by high-pressure and high-temperature techniques according to the current advantages, limitations and challenges in the experiment.