arXiv subjects

A. A. Shiryaev

Publications and source records attributed to A. A. Shiryaev.

12 recordsLinked to original sources

arXiv2026

Diamond crystal with Y-defects: spectroscopy and transmission electron microscopy

The paper presents results of investigation of a natural Ib-IaA diamond containing Y-defects from Yubileinaya kimberlite pipe, Yakutia. Analysis of spatial distribution of nitrogen-related A and C centers and intensity of Infra-red absorption at Raman frequency (1332 cm-1) reveals anticorrelation between these defects. Transmission electron microscopy of a zone with abundant Y-defects shows presence of dislocations in various configurations and numerous clusters of point defects generated by non-conservative dislocation motion. Extended defects with shape resembling thin (1-3 nm) rhombic plates with the largest dimension up to 20 nm are observed. Analysis of contrast of these defects shows that they represent nanosized voids (vacancy clusters). It is suggested that the defects were formed by annihilation of dislocation dipoles with subsequent growth by consumption of vacancies produced by non-conservative motion of dislocations. Upon excitation by 787 nm laser, numerous narrow photoluminescecne lines are observed between 800-900 nm; their intensity and position show pronounced spatial heterogeneity on scale of few microns. Qualitatively similar behaviour of photoluminescence was earlier noted for hydrogenated nanodiamonds. It is suggested that unusual behaviour of the luminescence lines may be explained by recombination processes at internal walls of the discovered nanovoids.

cond-mat.mtrl-sci↗

arXiv2025

Trace Element Behavior during Shock Transformation of Zircon to Reidite

Large single crystals of natural zircon were shock-loaded at 13.6 and 51.3 GPa in planar geometry. No structural changes were observed after loading at 13.6 GPa. Loading to 51.3 GPa resulted in zircon transformation to a denser scheelite-structured phase, reidite. The investigation of reidite samples by X-ray diffraction, Raman, photo- and cathodoluminescence spectroscopies revealed segregation of some trace cations (such as REE) on planar defects during the transformation. The segregation has occurred in a laboratory experiment without long-term annealing after the shock loading. A possible mechanism of the segregation of trivalent trace cations assumes local violation of charge balance during the zircon-reidite reconstructive transformation, which is accompanied by changes in the topology of polyhedra and second coordination spheres (Si-Zr). This results in expulsion of a fraction of the trace elements into energetically expensive interstitial positions with high diffusivity even at relatively low temperatures.

cond-mat.mtrl-sci↗

arXiv2024

Diamond phase in space and the possibility of its spectroscopic detection

The eventual presence of the diamond carbon allotrope in space is discussed in numerous theoretical and experimental studies. The review summarizes the principal mechanisms of nanodiamond formation and experimental results of spectroscopic and structural investigations of nano- and microdiamonds from meteorites. The size dependence of diamond spectroscopic properties is discussed. Infrared spectroscopy allows detection of C-H bonds on surfaces of hot nanodiamond grains. Spectroscopic observation of nitrogen-related point defects in nanodiamonds is very challenging; moreover, such defects have never been observed in nanodiamonds from meteorites. At the same time, photoluminescence and, eventually, absorption of some impurity-related defects, in particular, of the silicon-vacancy (SiV) center, observed in real meteoritic nanodiamonds opens the possibility of diamond detection in astronomical observations.

astro-ph.EP↗

arXiv2022

Temperature dependence of Fano resonance in nanodiamonds synthesized at high static pressures

Temperature dependence of Fano resonance, recently discovered in infra-red (IR spectra of nanodiamonds synthesized from chloroadamantane at high static pressures, is investigated. For the first time, marked variations of the resonance parameteres are observed. On heating, the shape of the Fano resonance changes considerably; the effect completely disappears above 350 C, but is recovered after cooling to ambient conditions. Such behaviour implies that assignment of the Fano effect to the surface transfer doping mechanism is not very plausible for the studied samples. The resonance shape varies due to strong temperature dependence of the difference of frequencies of IR-active "bright" and Raman-active "dark" modes of nanodiamond. The frequency of the Raman "dark" mode is only weakly temperature-dependent.

cond-mat.mes-hall↗

arXiv2022

Size-dependent thermal stability and optical properties of ultra-small nanodiamonds synthesized under high pressure

Diamond properties down to the quantum-size region are still poorly understood. High-pressure high-temperature (HPHT) synthesis from chloroadamantane molecules allows precise control of nanodiamond size. Thermal stability and optical properties of nanodiamonds with sizes spanning range from $<$1 to 8 nm are investigated. It is shown that hypothesis about enhanced thermal stability of nanodiamonds smaller than 2 nm is incorrect. The most striking feature in IR absorption of these samples is the appearance of an enhanced transmission band near the diamond Raman mode (1332 cm$^{-1}$). Following previously proposed explanation, we attribute this phenomenon to the Fano-effect caused by resonance of diamond Raman mode with continuum of conductive surface states. We assume that these surface states may be formed by reconstruction of broken bonds on the nanodiamond surfaces. This effect is also responsible for the observed asymmetry of Raman scattering peak. he mechanism of nanodiamond formation in HPHT synthesis is proposed, explaining pecularities of their structure and properties.

cond-mat.mtrl-sci↗

arXiv2021

Fano-type effect in hydrogen-terminated pure nanodiamond

Two novel properties, unique for semiconductors: a negative electron affinity [1-2], and a high p-type surface electrical conductivity [3-4], were discovered in diamond at the end of the last century. Both properties appear when the diamond surface is hydrogenated. A natural question arises: is the influence of the surface hydrogen on diamond limited only to the electrical properties? Here, we report the first observation of a transparency peak at 1328 cm-1 in IR absorption of hydrogen-terminated pure (undoped) nanodiamonds. This new optical property is ascribed to Fano-type destructive interference between zone-center phonons and free carriers (holes) appearing in the near-surface layer of hydrogenated nanodiamond. Our work opens the way to exploring the physics of electron-phonon coupling in undoped diamonds and promises the application of the H-terminated nanodiamonds as a new optical material with an induced transparency in IR optical range.

physics.optics↗

arXiv2021

Formation and characterization of an Al-rich metastable phase in Al-B phase diagram

Vacuum heat treatment of mechanically-alloyed powders of boron and aluminum leads to formation of a metastable Al-rich phase, which can be quenched. Its structure, composition, and thermal stability are established. With chemical formula Al1.28B the rhombohedral phase is unusually rich in Al. Parameters of the unit cell determined from X-ray powder diffraction are: a=18.3464(19) Å, c=8.9241(9) Å, 2601.3(6) Å3, space group R-3. It is stable at heating up to 630 °C. It is suggested that this phase is an important intermediate step in formation of AlB2 and, eventually, of other borides and its nucleation and thermal stability are explained by high elastic energy hindering formation of equilibrium phases at low temperatures.

cond-mat.mtrl-sci↗

arXiv2017

Anomalous enhancement of nanodiamond luminescence upon heating

Characteristic photoluminescence (PL) of nanodiamonds (ND) of very different origin (detonation, HPHT, extracted from meteorite) was studied in situ at high temperatures in the range 20-450C. Luminescence was excited using 473 nm laser and recorded in the range 500-800 nm. In contrast to decrease of point defect PL in bulk diamond with temperature, we found that the nanodiamond luminescence related to ND surface defects increases almost an order of magnitude upon heating to 200-250 C. The observed effect reveals that water adsorbed on ND surfaces efficiently quenches photoluminescence, water desorption on heating leads to dramatic increase of the radiative de-excitation.

cond-mat.mtrl-sci↗

arXiv2015

Photoluminescence of silicon-vacancy defects in nanodiamonds of different chondrites

Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (less than 2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamonds populations. Annealing of separates in air eliminates surface sp2-carbon, consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (< 250 °C) nanodiamonds in space.

astro-ph.SR↗

arXiv2012

Infra-red reflectance and emissivity spectra of nanodiamonds

Reflectance and emissivity spectra of nanodiamonds powder were measured in a dedicated setup at temperatures up to 873 K. The spectra are characterised by presence of sharp bands due to surface-bound functional groups. Thermal desorption of oxygen-containing groups lead to corresponding spectral changes. The maximal emissivity of nanodiamond powder reaches 0.985.

cond-mat.mtrl-sci↗

arXiv2011

Spectroscopic study of impurities and associated defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) meteorites

The results of spectroscopic and structural studies of phase composition and of defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapour Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the "silicon" defect) is observed in MND by photoluminescence spectroscopy.

cond-mat.mes-hall↗

arXiv2011

Depth concentrations of deuterium ions implanted into some pure metals and alloys

Pure metals (Cu, Ti, Zr, V, Pd) and diluted Pd-alloys (Pd-Ag, Pd-Pt, Pd-Ru, Pd-Rh) were implanted by 25 keV deuterium ions at fluences in the range (1.2÷2.3)x1022 D+/m2. The post-treatment depth distributions of deuterium ions were measured 10 days and three months after the implantation using Elastic Recoil Detection Analysis (ERDA) and Rutherford Backscattering (RBS). Comparison of the obtained results allowed to make conclusions about relative stability of deuterium and hydrogen gases in pure metals and diluted Pd alloys. Very high diffusion rates of implanted deuterium ions from V and Pd pure metals and Pd alloys were observed. Small-angle X-ray scattering revealed formation of nanosized defects in implanted corundum and titanium.

cond-mat.mtrl-sci↗