Equilibrium vacancy concentration in disordered binary alloys

The equilibrium vacancy concentration in disordered binary alloy is calculated in this paper. The calculations are performed in the configuration approximation, explicitly taking into account various types of vacant site neighborhoods. The self-diffusion coefficient is determined as a function of alloy composition.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 79–83, May, 1972.     

Equilibrium vacancy concentration on the surface of a binary substitution alloy with a deposited film

The equilibrium concentration of vacancies in a surface layer of a binary substitution alloy on which a monatomic film has been deposited is calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 54–59, October, 1991.     

Thermal expansion measurements for estimating vacancy concentration in X-ray irradiated KCl single crystals

A sensitive capacitance technique is used for measuring changes in length (Δl) of KCl single crystals with temperature in the region 30–300°C. These measurements have been taken on KCl in (i) as-cleaved (ii) X-ray irradiated (iii) quenched and X-ray irradiated conditions (X-ray irradiation was always done at room temperature (≈ 30°C). The linear coefficient of thermal expansion (α) of the as-cleaved sample is 40.8 × 10^-6°C^-1. Variation of Δl with temperature in X-ray irradiated crystal shows two regions: (a) 30–180°C where α is 48.1 × 10^-6°C^-1, (b) 180–300°C where α is 40.4 × 10^-6°C^-1. Similar behaviour is exhibited by quenched and later X-ray irradiated KCl the first region is up to 140°C, beyond which the second region takes over. From these data, concentration of vacancies in X-ray irradiated KCl at room temperature is calculated to be 3.4 × 10¹⁷ cm^-3 which is in fairly good agreement with the value obtained from F-band absorption measurements on the sample. An attempt has been made to understand these results.     

On the vacancy concentration in ice

Based on the diffusion constant for self-diffusion in ice, which is believed to take place by a vacancy mechanism, we estimate the relative vacancy concentration near the melting point to be at least ～ 10^?6, i.e. much higher than previous estimates of about 10^?10.     

Estimation of binding energy between a dislocation and vacancy and concentration of vacancies from ultrasonic attenuation measurements

Cottrell’s binding energy between a dislocation and vacancy and concentration of vacancies has been calculated using ultrasonic attenuation measurements in single crystals of pure tin at 300K for frequencies varying from 3 to 50 MHz and at different dislocation densities.     

Dependence of nitrogen vacancy color centers on nitrogen concentration in synthetic diamond

Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo-C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm^-1 and contained only the sp³ hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was < 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm^-1. Furthermore, neither the NV⁰ nor the NV^- optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV⁰ and NV^- optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV^- color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV^-/NV⁰ ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV^- optical color centers.     

Detection of vacancy clustering by combined PAC and lattice location measurements

The formation of impurity-vacancy agglomerates starting with the trapping of monovacancies was studied using a combination of three complementary techniques applied to the system InCu: Perturbed -angular correlation, ion channeling and channeling of conversion electrons. This results in an almost complete picture of the first stage of vacancy agglomeration at In impurities in Cu.This work was supported by the Bundesminister für Forschung und Technologie.     

Positron angular correlation measurements on single-crystal aluminum at various temperatures

We have tested the trapping model by comparing the temperature dependence of the peak and the tail of the angular correlation curve from single crystal aluminum. The integral over the tail decreased as the integral over the peak increased with temperature, in such a way that the same vacancy formation energy could be deduced from both integrals. Paper B6 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973). Case Western Reserve University, Cleveland, Ohio, USA     

强流脉冲电子束辐照诱发多晶纯铝中的空位缺陷簇结构

利用强流脉冲电子束（HCPEB）技术对多晶纯铝样品进行辐照,采用透射电子显微镜详细分析了辐照诱发的空位簇缺陷.HCPEP辐照后,在辐照表层内形成了大量的四方形空位胞,其间包含位错圈和堆垛层错四面体（SFT）等类型的空位簇缺陷.1次辐照后,空位胞内产生空位型位错圈,5次辐照则主要产生SFT;10次辐照后,空位胞内产生的空位簇缺陷主要是位错圈,局部区域也观察到了SFT缺陷,在产生SFT的附近区域具有很低的位错密度或者几乎无位错出现.HCPEB辐照产生的瞬间加热和冷却诱发了幅值极大且应变速率极高的应力,这一因素 关键词： 强流脉冲电子束 多晶纯铝 空位簇缺陷 堆垛层错四面体     

Self-diffusion measurements in In_2O_3 isotopic heterostructures:Oxygen vacancy energetics

正As a prototypical transparent conducting oxide (TCO), In2O3after heavily doped with Sn exhibits a priority in optoelectronic applications involving organic light emitting diodes(OLED) and organic photovoltaics (OPVs)[1,2]. Mean-     

Dielectric properties of multilayered SrTiO3 thin films with graded oxygen vacancy concentration

SrTiO₃ (STO) thin films were homo-epitaxially grown on Nb-doped STO substrates at varying oxygen pressures, and the effect of oxygen vacancy concentration on the dielectric properties of the STO thin films was studied and is presented herein. Although the STO thin films with low oxygen vacancy concentration demonstrated low zero-bias permittivity, low dielectric tunability, and high dielectric dissipation, the STO thin films, however, could withstand a large electric field. While the STO thin films with high oxygen vacancy concentration exhibited reduced dielectric loss and high dielectric tunability, they exhibited a low breakdown electric field. In order to make use of the respective advantages of the STO thin films with different oxygen vacancy concentrations, a trilayered structure was obtained by varying the oxygen pressure during deposition and combining one thin STO layer with large oxygen vacancy concentration sandwiched by two STO thin films with low oxygen vacancy concentration. The microstructure and dielectric properties of the trilayer were then studied. X-ray diffraction analysis indicated that the trilayer was a relaxed STO multilayer formed by two STO thin layers with different lattice parameters. An improved optimization of high tunability and low loss was achieved in the relaxed trilayer. PACS 77.84.Bw; 68.55; 77.22.Ch; 68.35.Ct; 74.80.Dm     

Equilibrium free energies from nonequilibrium measurements using maximum-likelihood methods

We present a maximum likelihood argument for the Bennett acceptance ratio method, and derive a simple formula for the variance of free energy estimates generated using this method. This derivation of the acceptance ratio method, using a form of logistic regression, a common statistical technique, allows us to shed additional light on the underlying physical and statistical properties of the method. For example, we demonstrate that the acceptance ratio method yields the lowest variance for any estimator of the free energy which is unbiased in the limit of large numbers of measurements.     

The effect of thermal redistribution of various interstitial impurities on equilibrium vacancy concentration in BCC substitutional-interstitial alloys

The equilibrium vacancy concentration in bcc substitutional-interstitial alloys is calculated taking into account thermal redistribution of the interstitial component in different types of interstices. The conditions where this effect gives rise to a decrease or increase in vacancy concentration are formulated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 89–92, April, 2007.     

Oxygen vacancy and dopant concentration dependent magnetic properties of Mn doped TiO2 nanoparticle

Mn doped TiO₂ nanoparticles are synthesized by sol–gel method. Incorporation of Mn shifts the diffraction peak of TiO₂ to lower angle. The position and width of the Raman peak and photoluminescence intensity of the doped nanoparticles varies with oxygen vacancy and Mn doping level. The electron spin resonance spectra of the Mn doped TiO₂ show peaks at g = 1.99 and 4.39, characteristic of Mn²⁺ state. Reduction in the emission intensity, on Mn doping, is owing to the increase of nonradiative oxygen vacancy centers. Mn doped TiO₂, with 2% Mn, shows ferromagnetic ordering at low applied field. Paramagnetic contribution increases as Mn loading increases to 4% and 6%. Temperature dependent magnetic measurement shows a small kink in the ZFC curve at about 40 K, characteristic of Mn₃O₄. The ferromagnetic ordering is possibly due to the interaction of the neighboring Mn²⁺ ions via oxygen vacancy (F⁺ center). Increase in Mn concentration increases the fraction of Mn₃O₄ phase and thereby increases the paramagnetic ordering.     

Radical concentration measurements in hydrocarbon diffusion flames

Absolute OH· concentrations and relative H-atom and O-atom profiles have been measured in a laminar, co-flowing methane/air diffusion flame burning at atmospheric pressure. Laser absorption and laser-induced fluorescence methods were used to probe the A ² X ²II_itransition in OH·. The maximum OH· concentration is found to be 1.8±0.2 ×10¹⁶ cm^–3 (mole fraction =5.0×10^–3) at a temperature of 2080 K, which is twice the value calculated assuming local total equilibrium but less than half that predicted from partial equilibrium (O₂+H₂ 2OH·). Multiphoton ionization (2+1 process at 243 nm) has been used to detect H atoms, while laser-induced fluorescence at 845 nm excited by two-photon absorption at 226 nm was employed to observe O atoms. In both cases it was found that low photon intensities (2×10⁸W/cm²) and a retroreflected beam, Doppler-free geometry was required in order to avoid the photolytic production of the species of interest. For all of the concentration profile data it is necessary to correct the raw signals for variations in collisional quenching. In the case of the multiphoton ionization measurements the variation in electron detection sensitivity as a function of flame position must be accounted for as well. Establishing absolute H-atom and O-atom concentrations is discussed in terms of partial equilibrium considerations and detailed flame structure calculations.Formerly the National Bureau of Standards