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The surface morphology of vicinal (100) single-crystal diamond surfaces homoepitaxially grown in a microwave plasma-assisted chemical vapor deposition (MPACVD) reactor is studied. High-pressure and high-temperature (HPHT) single-crystal diamond substrates produced by different vendors are used as substrates. Prior to the CVD growth, substrates were mechanically polished and etched in a separate inductively coupled plasma/reactive ion etching (ICP/RIE) tool using an Ar/Cl 2 gas mixture. The impact of (a) ICP etching regime of the HPHT substrate, (b) substrate polishing, and (c) the HPHT substrate misorientation (off-axis) vicinal angle on the surface morphology is examined. It was found that the ICP etching removes polishing-induced defects in the bulk and also removes diamond particles which are left on the surface of single-crystalline diamond after polishing. The morphology of the surface of the homoepitaxial CVD diamond grown on a substrate, which is free of polishing defects, depends not only on the parameters of the growth process (substrate temperature, composition of the gas mixture, pressure, etc.), but also on the value and direction of the off-axis angle.

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The reactions of bis(borohydride) complexes [(RN=)Mo(BH4)2(PMe3)2] (4: R = 2,6-Me2C6H3; 5: R = 2,6-iPr2C6H3) with hydrosilanes afford new silyl hydride derivatives [(RN=)Mo(H)(SiR'3)(PMe3)3] (3: R = Ar, R'3 = H2Ph; 8: R = Ar', R'3 = H2Ph; 9: R = Ar, R'3 = (OEt)3; 10: R = Ar, R'3 = HMePh). These compounds can also be conveniently prepared by reacting [(RN=)Mo(H)(Cl)(PMe3)3] with one equivalent of LiBH4 in the presence of a silane. Complex 3 undergoes intramolecular and intermolecular phosphine exchange, as well as exchange between the silyl ligand and the free silane. Kinetic and DFT studies show that the intermolecular phosphine exchange occurs through the predissociation of a PMe3 group, which, surprisingly, is facilitated by the silane. The intramolecular exchange proceeds through a new non-Bailar-twist pathway. The silyl/silane exchange proceeds through an unusual Mo(VI) intermediate, [(ArN=)Mo(H)2(SiH2Ph)2(PMe3)2] (19). Complex 3 was found to be the catalyst of a variety of hydrosilylation reactions of carbonyl compounds (aldehydes and ketones) and nitriles, as well as of silane alcoholysis. Stoichiometric mechanistic studies of the hydrosilylation of acetone, supported by DFT calculations, suggest the operation of an unexpected mechanism, in that the silyl ligand of compound 3 plays an unusual role as a spectator ligand. The addition of acetone to compound 3 leads to the formation of [trans-(ArN)Mo(OiPr)(SiH2Ph)(PMe3)2] (18). This latter species does not undergo the elimination of a Si-O group (which corresponds to the conventional Ojima's mechanism of hydrosilylation). Rather, complex 18 undergoes unusual reversible β-CH activation of the isopropoxy ligand. In the hydrosilylation of benzaldehyde, the reaction proceeds through the formation of a new intermediate bis(benzaldehyde) adduct, [(ArN=)Mo(η(2)-PhC(O)H)2(PMe3)], which reacts further with hydrosilane through a η(1)-silane complex, as studied by DFT calculations.

Platinum and platinum based materials are of fundamental importance for modern and developed catalysts, fuel cells, sensors, hydrogen production and storage systems, and nanoelectronic devices. The subnanosize cluster Pt24 was considered as a model of the prospective catalytic system based on the oxide and carbide supported Pt nanoparticles (Pt NPs) or Pt NPs with soft spacers anchored to their surface. Structural, electronic, thermodynamic, and spectral properties of the adsorption complexes of molecular and atomic hydrogen on Pt NPs have been studied using the DFT method (the BLYP functional with the 6-31G­(p) basis for H and the CRENBS pseudopotential for Pt atoms). On this basis, the adsorption energies for molecular hydrogen at the Pt NPs along with the energies and activation energies of its dissociation were estimated and the pathways of activationless dissociative adsorption were found. The full map of adsorption energies of atomic hydrogen at the various surface regions of Pt24 was obtained. The structures of transition states for the rearrangements between the adsorption complexes were located, and the activation energies for surface migration were calculated. Additionally, several ways of subsurface diffusion of H atoms inside the Pt24 cluster were considered which allows estimating the diffusion parameters and the probability of the hydrogen spillover when the cluster surface is highly covered by ligands restricting the surface migration. The IR and Raman spectra of most favorable adsorption complexes were simulated to provide the possibility of an experimental validation of the results obtained.

The technology of wet etching allowing fabrication of stand-alone BSCCO mesa structures was proposed. The produced mesas can be made much thicker than ones usually being studied. The time required for the fabrication is much smaller in comparison with the standard method of ion milling. The process used is controllable which provides acceptable precision of mesa fabrication. The IV characteristics of the sample showing Josephson nature were obtained. The qualitative comparison with characteristics of similar structures fabricated by other groups was carried out.

The results of a study of diamond p–i–n diode with a nitrogen‐doped intrinsic region on a substrate with the (001) orientation are presented. When the forward voltage is applied to the diode, a high current density of about 103 A cm−2 is obtained. Two narrow lines are detected in the electroluminescence spectrum of the p–i–n diode: one at a wavelength of 575 nm corresponding to the emission of the NV center (nitrogen‐vacancy color center) in a neutral charge state, and the second narrow line, which previously has not been observed in the electroluminescence spectra, at a wavelength of 533 nm. The line widths at room temperature are about 7 and 3 nm, respectively. By comparing the emission intensities of NV centers using the same optical registration system for electroluminescence and photoluminescence, the emission rate of NV centers during electroluminescence is estimated to be about 106 photon s−1, which allows to consider a diode of such design as a possible candidate to create single‐photon sources.

We report on the first experimental observation of terahertz (THz) wave generation from bismuth mono- and polycrystalline samples irradiated by femtosecond laser pulses. Dependencies of the THz signal on the crystal orientation, optical pulse energy, incidence angle, and polarization are presented and discussed together with features of the sample surfaces. The optical-to-THz conversion efficiency was up to two orders of magnitude higher than for metal at a moderate fluence of ∼1  mJ/cm². We also found nonlinear effects not previously observed using other metal and semiconductor materials: (a) asymmetry of THz response with respect to a half-turn of a sample around its normal, (b) THz polarization control by orientation of the sample surface, and