Original termination of the detonation nanodiamond (DND) was changed by active chemical media interaction. Oxidation in boiling chloric acid, by hydrogen and chlorination by carbon tetrachloride vapor was applied. FTIR, TGA, and photoluminescence techniques revealed the DND functional termination changing. At hydrogenation treatment monofunctionally of the surface demonstrated. The totality of presented results demonstrates the possibility of substantial and controlled changes in the DND functional properties, for their subsequent use in the self-organization processes, at nanocomposites preparation and for other aims.

A radically new synthetic method, called the diamond chemical crystallization from gas phase, is described; the credit of its development is due to Russian researchers. The steps in its development and principal results of the studies in the diamond chemical crystallization and diamond coating deposition from gas phase are outlined.

Here we report the experimental study of a new superconductor, B-doped diamond. Subjecting a mixture of amorphous boron with graphite to a high-temperature and high-pressure treatment, we synthesized polycrystalline boron-doped diamond samples, whose sizes were suitable for specific heat measurements. For this kind of sample, we detected two specific heat anomalies at temperatures (∼4 K) closely corresponding to temperatures at which the resistance and magnetic susceptibility anomalies take place. The most probable origin of these specific heat anomalies is a bimodal B distribution in polycrystalline diamond. The correlation of physical properties, such as specific heat, electrical resistivity, and magnetic susceptibility, near the superconducting transition temperature is clear evidence of bulk superconductivity in these boron-doped diamond samples. Specific features in the low frequency range of Raman spectra correlate with superconducting properties of diamond. These features help to select heavily boron-doped CVD diamond films (DF) grown on (111) natural diamond, which exhibit superconductivity.

A short review on the diamond CVD origin, together with its state of the art and some prospects was given. New hybrid methods of the diamond CVD permit to gain 1.2 to 6 times of growth rate in comparison with ordinary diamond CVD's. Recent results on n-type diamond film synthesis through phosphorus doping in the course of the CVD process are briefly discussed. In comparison with high-pressure diamond synthesis, the CVD processes open new facets of the diamond as ultimate crystal for science and technology evolution. It was stressed that, mainly on the basis of new CVDs of diamond, the properties of natural diamond are not only reproduced, but can be surpassed. As examples, mechanical (fracture resistance), physical (thermal conductivity), and chemical (oxidation stability) properties are mentioned. Some present issues in the field are considered.

The action of subsidiary activation, basically electrical, on various types of CVD-diamond is surveyed. Depending on the character and the direction of action on the system "crystallization medium - crystal" two opportunities are distinguished: action on gas phase and on the surface of a growing crystal. It is marked, that the influence of subsidiary activation on the rate of crystallization of diamond can be manifested in the greater degree at high temperatures of crystallization and high concentrations of carbon in the gas phase. At use of various methods of activation and/or the crystallization conditions the considerable gain (2-6 times) in the linear growth rate of diamond films, and also change of their quality can be observed.

High-intensity activation of the vapor phase is a necessary condition for diamond synthesis in the customary chemical vapor deposition (CVD) of diamond. In this paper a novel approach to activated CVD (ACVD) of diamond based on the combined or hybrid ACVD techniques will be discussed.By hybrid diamond ACVD we mean a technique that employs more than one way of activating the crystallization medium. Together with the basic activation mode, the hybrid method includes different supplementary activation modes that influence the physical and physico-chemical processes in the vapor phase and also on the diamond crystal surface. The role of added activation in changing the growth kinetics of diamond film (DF) and microcrystals has been considered. The published research works and our own data are indicative of the remarkable influence of added activation in such hybrid ACVD techniques as chemical transport reaction, HF (Hot Filament) or DC arcjet in combination with electrical activation, and also in MW ACVD with the addition of ultraviolet-irradiation. Along with the increase in the DF growth rate there also may be changes in the constitution and crystalline perfection of DF and microcrystals grown by hybrid methods. Depending on the combination of the methods used as well as the ratio of the activation levels and crystallization temperature the linear growth rate of diamond can be raised by 1.2-6 times as compared to the rate gained via the single-activation technique. It is a striking fact that the added power of the secondary activation may amount from several to several tens of percent of the main activation power. In conclusion the possible reasons for the growth gain obtained in the novel hybrid ACVD of diamond will be considered. (C) 1999 Elsevier Science S.A. All rights reserved.

The Hall-effect and conductivity of diamond polycrystalline films doped by boron impurity (N-alpha congruent to 10(19) cm(-3)) were measured over a temperature range of 300 divided by 650 K. A temperature transition from the hopping epsilon(3) - conductivity to the hole transport through Impurity band formed by exited states of the accepters was observed. Analyzing the Hall- effect data by the model of mixed conductivity, the hole mobility (mu Eta congruent to 10 cm(2)/ V.s) in the band and energy gap between this band edge and the boron ground state level (congruent to 220 meV) were estimated.

Chemical and physicochemical approaches to diamond doping have been considered. For better previewing of boron and phosphorus atoms bonding in diamond lattice a method of prototype molecules was proposed. Four-coordinated compounds like, e.g. Na+[B(CH3)(4)](-) and [P(CH3)(4)]Cl-+(-) are much more close prototypes for state of boron and phosphorus in diamond lattice. In calculation of equilibrium redistribution coefficient both thermochemical (bond energy decrement) and geometrical (strain energy) factors can be concerned. The strain energy induced by substitutional phosphorus doping of diamond estimated on the base of elasticity theory is comparable with bond energy term.In AlN doping it is necessary to take into consideration the unintentional AlN doping by oxygen and, probably, hydrogen. These elements may compensate in particular acceptor centers, embarrassing the synthesis of AlN of semiconductor quality. The experimental results obtained by M.G.Spencer's team demonstrate effective doping of AlN by carbon with obtaining of p-type semiconductor.

Diamond coatings chemically vapor deposited onto WC-Co cemented carbides by use of specially developed barrier underlayers are described. Preliminary seeding the barrier underlayers with nano-grain diamond particles by laser ablation allows obtaining fine-grained and uniform diamond coatings. The diamond coatings obtained in this way have high adhesion to the cemented carbide substrate due to enhanced interaction between the underlayer, nano-grained diamond nuclei and gas phase employed in their plasma-assisted chemical vapor deposition.

Results on the structure, composition and properties of diamond films deposited onto WC-Co cemented carbides via special multilayer barrier interlayers preliminary seeded by nano-grained diamond particles are presented. The barrier interlayers comprise a layer adjacent to the substrate, which completely prevents substrate decarburization and Co diffusion from the substrate, and a diamond-bonding layer needed to obtain an enhanced adhesion of the PACVD diamond coating. Preliminary seeding the barrier interlayers with nano-grain diamond particles by use of a laser ablation technique allows a fine-grained, uniform and highly adherent diamond coating of high quality to be deposited by use of a conventional PACVD technique. Results on the nature of the interaction between the diamond nano-grained seeds and barrier interlayer are also presented.

A new method for diamond film preparation by laser ablation of a highly dispersive diamond target is proposed. Transmission and scanning electron microscopy, Raman and Auger spectroscopy data prove that the deposited film consists of cubic diamond. The density of diamond crystallites is 1011–1012cm−2. They were used as nucleation centres for subsequent CVD growth of thick diamond film.

p- and n-type diamond films (DF) were grown by vapour chemical transport method and from DC are discharge plasma. Maximum contents of doping elements in epitaxial DF (EDF) were 2.5, 1 and 0.02 wt% for B-, P- and S-doped EDF, respectively. Specific resistances of the EDF were 10−3, 101 and 103 Ω cm, respectively. The doping changes the growth rate and chemical properties of EDF. Doped EDF were investigated by spark mass-spectrometry, X-ray spectrometry, Rutherford backscattering and Hall-effect measurements. Electroabsorption and cathodoluminescence spectra were studied. DF with a highly distorted structure and dislocation p-type conductivity were grown from glow discharge plasma. B- and As-doped 1 mm size crystals were obtained by an ultra-high-pressure method. As produces multicharged donor centres with two energy levels. The crystals are prospective for sensors. Doping of diamond with B, C, P, Sb and Li was realised by ion implantation. The best p- and n-type layers doped with B and Li have carrier mobility of about 1000 cm2/V s. Acceptor dislocation centres can also be created by plastic deformation of diamond crystals. Specific resistance of such crystals can fall by up to 102 Ω cm. Combining the above-mentioned methods seems to be the most prospective way.

Semiconducting diamond structures — models of solid state electronic devices — were made by means of chemical crystallization of diamond films from the gaseous phases1. Doping by boron and phosphorus during growth made it possible to obtain homoepitaxial diamond films of p-and n-type conductivity2. The simplest device of this type is a thermistor. There are diamond thermistors, made of synthetic crystals doped by boron, obtained by the method of superhigh pressures. Diamond thermistors appear to be a good starting device owing to their ability to operate over a wide temperature range, high thermal stability and low inertia due to high thermal conductivity.