V. Yu. Yurov

Atomic structure of saturated chlorine monolayer on Ag(111) surface

Abstract STM and LEED techniques were applied to study the structure of saturated chlorine monolayer formed on Ag(111) as a result of Cl 2 adsorption at room temperature. We present for the first time atomic resolution STM images of chlorinated Ag(111) surface obtained in ultra-high vacuum conditions. The structure of chlorine layer was identified by means of a Fourier analysis of the STM images as Ag(111)–(17 × 17)-Cl. The structure of saturated chlorine monolayer remains unchanged for Cl 2 exposures up to 100 000 L and coexists with AgCl islands on Ag(111) surface.

Modeling of electronic density of states for single-wall carbon and boron nitride nanotubes

The electronic density of states is calculated for all possible geometric configurations of single-wall carbon and boron nitride nanotubes. The calculation is based on the numerical differentiation of the two-dimensional dispersion relations for graphite and hexagonal boron nitride. The differentiation is performed for all allowed values of the wave vector using the π-electron approximation. For the particular carbon nanotubes chosen as examples, a good agreement is demonstrated between the calculated values of energy spacing of the symmetric van Hove singularities in the density of states and the experimental data obtained from the resonance Raman scattering study.

Formation of Nanoislands in the Course of Copper Deposition on a Cu(111)-(9 ¥ 9)-Ag Surface

The process of copper deposition on a structured Cu(111)-(9 × 9)-Ag surface, which represents a (9 × 9) loop dislocation network, is studied by scanning tunneling microscopy. It is found that, when the substrate temperature is 100 K and the copper coverage is 0.1–0.4 of a monolayer, islands of a size no greater than 50 Å are formed at the Ag/Cu(111) interface. The islands remain stable as the sample is heated to room temperature. The shape and boundaries of the nanoislands follow the initial surface superstructure and are determined by the nonuniformity of the interaction of the upper silver layer with the copper substrate. The mechanism of island formation and the origin of their stability are explained in terms of the atom exchange between the adsorbate and substrate.

Growth of 4″ diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters, and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230–380 K. The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra. Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples, respectively. TC, as high as 1950 ± 230 W m−1 K−1 at room temperature, is measured for the most perfect material. A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established. A F POPOVICH V G RALCHENKO V K BALLA A K MALLIK A A KHOMICH A P BOLSHAKOV D N SOVYK E E ASHKINAZI V Yu YUROV

Confocal luminescence study of nitrogen-vacancy distribution within nitrogen-rich single crystal CVD diamond

Confocal photoluminescence (PL) microscopy was used to study a distribution of negatively charged nitrogen-vacancy (NV−) defects within a surface and in a cross section of a homoepitaxial chemical vapor deposition (CVD) diamond layer intentionally grown with a nitrogen concentration close to the solubility limit. A variation in the PL intensity within the whole sample was found to exceed no more than 30% of the intensity maximum. The diamond layers with densely packed NV− arrays are a promising material platform for the design of highly sensitive magnetic field and temperature sensors, as well as for using this material in quantum optics and informatics technologies based on NV− spins.

Excitation of oscillations of an immiscible liquid interface by a pulsed ultrasound beam parallel to the interface

For several pairs of immiscible liquids, a new opportunity to excite oscillations of their interface by ultrasound pulses propagating parallel to the interface has been discovered experimentally. A plane ultrasound transducer is placed so that the interface between liquids halves its aperture. The evolution of the shape of the interface oscillations under the variation of the amplitude and duration of excitation pulses, as well as of the distance from the transducer, has been analyzed. The possibility of the excitation of various modes of the interface oscillations in a bounded volume has been revealed.

Near-infrared refractive index of synthetic single crystal and polycrystalline diamonds at high temperatures

We measured the refractive index n(T) and thermo-optical coefficient β(T) = (1/n)(dn/dT) of high quality synthetic diamonds from room temperature to high temperatures, up to 1520 K, in near-infrared spectral range at wavelength 1.56 μm, using a low-coherence interferometry. A type IIa single crystal diamond produced by high pressure–high temperature technique and a transparent polycrystalline diamond grown by chemical vapor deposition were tested and revealed a very close n(T) behavior, with n = 2.384 ± 0.001 at T = 300 K, monotonically increasing to 2.428 at 1520 K. The n(T) data corrected to thermal expansion of diamond are well fitted with 3rd order polynomials, and alternatively, with the Bose-Einstein model with an effective oscillator frequency of 970 cm−1. Almost linear n(T) dependence is observed above 800 K. The thermo-optical coefficient is found to increase monotonically from (0.6 ± 0.1) × 10−5 K−1 (300 K) to (2.0 ± 0.1) × 10−5 K−1 (1300 K) with a tendency to saturation at >1200 K. These β(T) v...

SPM probe-assisted surface nanostructuring of boron-doped diamond

Surface modification of conductive boron-doped diamond has been conducted using the electrical field of the probe of a scanning probe microscope (SPM) at varying relative humidity (RH) of the ambient environment. It has been found that, under the action of positive polarity pulses applied to the sample via a grounded SPM probe, the sample material undergoes modification. The modification pattern depends on atmospheric RH: low (up to 32%) and high humidity values (above 35%) lead to the formation of cavities and protrusions, respectively. It has been found that the resulting protrusions exhibit temporary instability; that is, a protrusion is partially transformed into an array of nanoobjects. The mechanism of modification of boron-doped diamond–local anodic oxidation–has been discussed.