Ab initio Calculation of Impurity–Vacancy Complexes in Diamond at High Pressure

Journal of Experimental and Theoretical Physics - Optical centers in diamond are possible candidates for single-photon emitters for applications in quantum communication, biology, and medicine. The...     

Role of Activator and Vacancy Centers in the Decay of the Gamma Scintillators of CsI–Na Crystals

The influence of the concentration of an activator (C _NaI) and of plastic deformation on a change in the contribution of a slow component to the decay of the -scintillations of CsI–Na crystals was investigated, as well as the influence of C _NaI on a change in the shape of the luminescence excitation spectrum in the region of absorption of activator centers (AC) and of vacancy-related centers (VRC) and also on a change in the intercenter time of deexcitation of the centers indicated. It is shown that AC and VRC participate in the photoluminescence and -scintillations of CsI–Na crystals. In the -scintillations, AC are responsible for the component ₁ = 370 nsec, whereas the components ₁ = 460 nsec and ₂ 2 sec are associated with VRC. The reduction of ₁ from 770 to 560 nsec with an increase in C _NaI from 2·10^–3 to 3·10^–2 mole% and from 570 to 470 nsec after plastic deformation of the crystals ( = 5%) along the 111 axis is caused by a decrease in the number of VRC. The mechanisms underlying the -scintillations of the CaI–Na crystals containing AC and VRC and also the decrease in the number of VRC are discussed.     

Preparating Quantum Entanglement Between Microtoroidal-Resonator–Mediated Nitrogen-Vacancy Centers in Diamond

International Journal of Theoretical Physics - We propose a scheme to prepare entangled states between solid-state nitrogen-vacancy (NV) centers. In our scheme, NV centers are coupled to the...     

Mechanism of Formation of Carbon–Vacancy Structures in Silicon Carbide during Its Growth by Atomic Substitution

Physics of the Solid State - The mechanism of formation of carbon-vacancy structures in silicon carbide SiC from silicon vacancies that inevitably form during synthesizing SiC from Si by atomic...     

Laser Induced Damage in CVD Diamond Films

ＬａｓｅｒＩｎｄｕｃｅｄＤａｍａｇｅｉｎＣＶＤＤｉａｍｏｎｄＦｉｌｍｓＱＩＵＨｏｎｇＦＡＮＺｈｅｎｇｘｉｕ（ＳｈａｎｇｈａｉＩｎｓｔｉｔｕｔｅｏｆＯｐｔｉｃｓａｎｄＦｉｎｅＭｅｃｈａｎｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｐ．Ｏ．...     

Vacancy Aggregation in Diamond Films grown in CH4＋H2 Atmosphere by MPCVD

Transmission electron microscopy is applied to study the diamond film grown in a CH₄ and H₂ gaseous mixture by microwave plasma assisted chemical vapour deposition. Defects in the nanometre scale, dislocation loops, arefirst observed in diamond films. The dislocation loops are found to be of co-existence with planar defects and are next to the planar defects for {111} faceting grains. A possible mechanism is suggested to interpret the co-existence of dislocation loops with planar defects.     

Deposition of ZnO Films on Freestanding CVD Thick Diamond Films

For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.     

Charge Exchange of the Centers in Electron–Irradiated Zinc Selenide

The optical absorption induced by the photosensitive centers formed upon electron irradiation (E = 5 MeV, = 1.7·10¹⁸ cm^–2) of polycrystalline ZnSe has been studied. A comparison of the optical properties of the irradiated crystals with the known data for ZnS has allowed the assumption that the 496–, 563–, and 652–nm bands in ZnSe are associated with the anion vacancies being in different charge states. The ratio between the concentrations of the optical absorption centers in the crystals photoexcited at 80 K is determined by the electron traps participating in the processes of charge exchange of the vacancies.     

Behaviour of Self-Standing CVD Diamond Film with Different Dominant Crystalline Surfaces in Thermal-Iron Plate Polishing

Self-standing CVD diamond films with different dominant crystalline surfaces are polished by the thermal-iron plate polishing method. The influence of the dominant crystalline surfaces on polishing etfficiency is investigated by measuring the removal rate and final roughness. The smallest rms roughness of 0.14 μm is measured with smallest removal rate in the films with the initial （220） dominant crystalline surface. Activation energy for the polishing is analysed by the Arrhenius relation. It is found that the values are 170kJ/mol, 222kJ/mol and 214kJ/mol for the film with three different dominant crystalline surfaces. Based on these values, the polishing cause is regarded as the graphitization-controlling process. In the experiment, we find that transformation of the dominant crystalline surfaces from （111） to （220） always appears in the polishing process when we polish the （111） dominant surface.     

Formation of complexes in polyhydroxybutyrate–polyethylene glycol mixtures

Polyhydroxybutyrate–polyethylene glycol mixtures are studied. The formation of polymer complexes in these mixtures is revealed. Rheology, DSC, IR spectroscopy measurements demonstrate the presence of the hydrogen bonds between the polymers in the mixtures prepared from solutions is various solvents. A model of the polymer complex is proposed. The studied blends of polyhydroxybutyrate and polyethylene glycol can be used in medicine as carriers for the sustained delivery of drugs into the human body.     

The First Observation of 4f-Luminescence in New Heteronuclear Lanthanide–Germanium Complexes

New lanthanide–germanium complexes with diethylenetriaminepentaacetic acid (DTPA) have been synthesized and were characterized by means of elemental analysis, IR-, UV-absorption and luminescent spectroscopy. The 4f-luminescence of heteronuclear Ln(Ge-DTPA)2 (Ln=Sm, Eu, Tb, Dy) complexes in aqueous solutions was investigated for the first time.     

ODMR Spectroscopy of NV<Superscript>−</Superscript> Centers in Diamond Under High MW Power

We have studied negatively charged nitrogen vacancy centers (NV\(^-\) centers) in diamond using the technique of optically detected magnetic resonance (ODMR). Due to the use of the MW power amplifier we have easily observed in the ODMR spectrum all the lines known to date, including the lines of the excited state of the NV\(^-\) centers. The g values and the hyperfine interaction constants of the ground and the excited triplet states of the NV\(^-\) center are given. Hamiltonian parameters of the ground and the excited triplet states of the NV\(^-\) center at ambient temperature have been confirmed and refined. In addition, an evidence of a slight g value asymmetry of the excited state of the NV\(^-\) center has been obtained.     

Structure Formation in Equimolar Mixture of HfC–ZrC–TiC–NbC Carbides

Russian Physics Journal - Structure formation during hot pressing of an equimolar powder mixture HfC–ZrC–TiC–NbC in the temperature range from 1400 to 1900°C is investigated....     

Modulated and Incommensurate Superstructures of Atomic–Vacancy Ordering in Refractory Transition Metal Carbides

Journal of Experimental and Theoretical Physics - A model of resonance absorption of laser radiation in a plasma involving the deformation of the density profile by the ponderomotive force has been...     

Effect of Laser Radiation near 1.5 µm on the Photoluminescence Parameters and the Ensemble of NV Centers in Diamond

JETP Letters - The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied...     

Formation of Composites in the System of Organic Europium Complexes–Silica

Lanthanide doped sol–gel glasses are an attractive type of luminescent material which can be processed at ambient temperatures. However, it is very difficult to obtain a uniform distribution of the complexes in glass materials because of their strong tendency to cluster formation. This problem can be solved by covalently linking of lanthanide complexes to silica matrix. In our work such materials were obtained by the sol–gel method of hydrolysis and polycondensation of tetramethoxysilane with europium complexes containing trimethoxysilyl groups. For this purpose we synthesized a novel ligand — (N-3-trimethoxysilylpropyl)-N′-1,10-phenanthroline-5-yl-thiocarbamide — and corresponding complexes [Eu(tta)₃phen′]Cl₃ and [Eu(pta)₃phen′]Cl₃. Our approach enabled us to simplify the synthetic procedure. A number of uniform samples showing intense luminescence have been obtained and the concentration dependence of their luminescence has been studied.     

Formation of Color Centers and Molecular Complexes with a Weak Hydrogen Bond in Lithium Fluoride Crystals Depending on the Form of OH<Superscript>¯</Superscript> Inclusion

The form of oxygen-containing inclusions in the LiF crystal was shown to be determined by the laws of isomorphic substitution and impurity accumulation in a melt during crystal growth in open air. Color centers and hydrogen-bonded complexes of different types appear in the LiF crystal after irradiation depending on the form of OH^– and Mg²⁺ inclusions. The radiative decay of OH^– ions and the properties of molecular complexes (MCs) with a weak hydrogen bond are responsible for the decreased efficiency of formation of the F- and F₂-color centers and increased concentration of the positively charged F ₂ ⁺ - and F ₃ ⁺ -centers. Radiochemical reactions involving hydrogen and fluorine atoms and ions that compete with the formation of color centers were presented.     

Formation of sub-surface silver nanoparticles in silver-doped sodium–lead–germanate glass

The formation of silver nanoparticles in 60GeO₂–20PbO–20Na₂O bulk glass doped with 0.15 wt% of Ag has been studied by optical methods in the near ultraviolet-to-near infrared and mid-infrared ranges. A clear optical absorption band, which grows when increasing the annealing temperature, is observed around 460 nm, as a consequence of the surface plasmon resonance in the Ag nanoparticles. From the simultaneous analysis of optical transmittance and spectroscopic ellipsometry spectra in the near ultraviolet-to-near infrared range, it is demonstrated that the nanoparticles are surprisingly formed only in a thin layer (some tens of nm thick) underneath the sample surfaces. The potential of such a simultaneous optical analysis for determining the localization of the nanoparticles in glasses of any nature is underlined. Based on the results of a complementary mid-infrared spectroscopy characterization, the processes involved in silver migration to the surfaces and further aggregation to form nanoparticles are discussed.     

Color Glass Condensate in Schwinger–Keldysh QCD

Within the Schwinger–Keldysh representation of many-body QCD, it is shown that the leading quantum corrections to the strong classical color field are “classical” in the sense that the fluctuation field still obeys the classical Jacobi-field equation, while the quantum effects solely reside in the fluctuations of the initial field configurations. Within this context, a systematic derivation of the JIMWLK renormalization group equation is presented. A clear identification of the correct form of gauge transformation rules and the correct form of the matter-field Lagrangian in the Schwinger–Keldysh QCD is also presented.