Nickel diffusion in samarium sulfide

The diffusion of nickel atoms in samarium monosulfide (SmS) has been studied for the first time. Using the sequential layer removal technique, it was found that the coefficient of diffusion of the ⁶³Ni radioactive isotope at a temperature of T = 1050°C amounts to D ～ 1.8 × 10^?10 cm²/s in SmS single crystals and to 5.3 × 10^?9 and 1.2 × 10^?10 cm²/s for the fast and slow diffusion components, respectively, in polycrystalline SmS. The process of nickel diffusion in thin polycrystalline SmS films was studied using an X-ray diffraction technique. The coefficient of diffusion at T = 400°C in thin-film samples according to these data is ～10^?13 cm²/s.     

An ultrasonic study of the diffusion of Ag in CdSe in the temperature range 20°–400 °C

The diffusion of Ag in CdSe has been studied using an ultrasonic technique. The diffusion coefficient was found to be D = 3 × 10^?4 exp (?0.53 eV/kT) cm² s^?1 Diffusion was found to be Fickian in the region up to a depth of 10^?2 cm and one diffusion mechanism was found to dominate. No significant anisotropy was found in diffusion coefficients measured parallel or perpendicular to the c-axis.     

Chromium diffusion in GaAs in an open system

We have studied chromium diffusion from a surface layer produced by thermal evaporation into n-type GaAs in a flowing inert-reducing atmosphere. The temperature dependences of the Cr diffusivity and solubility in GaAs are well represented by Arrhenius equations with D ₀ = 1.7 × 10^?2 cm²/s and Q _D = 1.43 eV for the diffusivity and C _Cr ⁰ = 8.9 × 10²¹ cm^?3 and Q _Cr = 1.22 eV for the solubility.     

Active wrapping paper against mango anthracnose fungi and its releasing profiles

Active wrapping papers varied in bio‐based coating materials (chitosan and carboxymethyl cellulose) and vanillin concentrations (0.5%, 1.0%, 2.0%, and 4.0% (w/v)) were prepared to study their antifungal effects and release properties. Chitosan‐coated paper with 1% (w/v) vanillin gave the best inhibition against mycelial growth of mango anthracnose fungi and could inhibit its conidiospores germination. The release of vanillin from a chitosan‐coated paper under different conditions of temperatures (13°C, 25°C, and 37°C), relative humidity (RH) (75%, 86%, and 96% RH), and pH values (pH 3.8, 5.2, and 6.2) was studied. Moreover, the vanillin release from the paper to mango fruit under an actual commercial storage condition (13°C, 90% RH) was also investigated. The predominant mechanism of vanillin release under low temperatures (13‐25°C) and all RH studied was a Fickian diffusion, whereas the high temperature (37°C) and in all buffers varying pH showed a non‐Fickian behaviour. Increasing temperature and RH enhanced in diffusion coefficient (D value) from 78.24 × 10^?10 to 162.10 × 10^?10 cm²/s and 42.87 × 10^?10 to 59.98 × 10^?10 cm²/s, respectively. Meanwhile, the increasing pH value reduced the D value from 233.87 × 10^?10 to 122.74 × 10^?10 cm²/s. The kinetic of vanillin release under an actual wrapping application exhibited a non‐Fickian behaviour, and the D value was considerably low (approximately 65.36 × 10^?12 cm²/s). The developed active wrapping paper can be great interest for food industry and is practically reasonable for postharvest mango fruits.     

Zinc diffusion in YBa2Cu3O7−x ceramics

The process of zinc diffusion in YBa₂Cu₃O_7?x ceramics with a porosity of 20–30% was studied in the temperature interval from 110 to 450°C using a ⁶⁵Zn radioactive tracer. The temperature dependence of the tracer diffusion coefficient is described by the relation D=5×10^?9 exp(?0.25 eV/kT) cm²/s. It is concluded that zinc migrates predominantly via pores and intergranular layers in the ceramics.     

Sorption-diffusion model of 137Cs uptake by a water body bottom in estimations of water contamination

For a sample including 22 lakes, the ¹³⁷Cs concentrations in water were determined by the sorption-diffusion model. The ¹³⁷Cs levels in waters of lakes of the Kola Peninsula and Karelian Isthmus are satisfactorily described by the suggested model at the distribution coefficient K _d of 4000 L kg^?1 and diffusion coefficient D of 1.0 × 10^?7 cm² s^?1 for 2–4-year exposure. For mid-latitude lakes, the ranges of K _d and D of ¹³⁷Cs were 6000–1200 L kg^?1 and 1.0 × 10^?7–0.2 × 10^?7 cm² s^?1, respectively. The ¹³⁷Cs concentration in water is determined by the major contribution of silts, which are characterized by high K _d of ¹³⁷Cs and by large thickness of sediments on the bottom of lake hollows, to the watter-bottom sorption system. After 2-year exposure of “Chernobyl” ¹³⁷Cs in lakes, its inventory in water relative to the amount that fell out in 1986 did not exceed 14% for deep lakes and 2–3.6% for shallow lakes.     

Role of diffusion-annealing temperature on the microstructural and superconducting properties of Cu-doped MgB2 superconductors

This study deals with not only investigate the effect of the copper diffusion on the microstructural and superconducting properties of MgB₂ superconducting samples employing dc resistivity as a function of temperature, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements but also calculate the diffusion coefficient and the activation energy of copper for the first time. Electrical-resistivity measurements indicate that both the room-temperature resistivity value and zero resistivity transition temperatures (T _c ) increase with increasing the diffusion-annealing temperature from 650 to 850?°C. SEM measurements show that not only the surface morphology and grain connectivity improve but also the grain size of the samples increases with the increase in the diffusion-annealing temperature up to 850?°C. As for the XRD results, all the samples contain the MgB₂ phase only and exhibit the polycrystalline superconducting phase with more intensity of diffraction lines, leading to the increasement in the lattice parameter a and c. Additionally, the diffusion coefficient is observed to increase from 6.81?×?10^?8 to 4.69?×?10^?7?cm²?s^?1 as the diffusion-annealing temperature increases, confirming that the Cu diffusion at lower temperatures is much less significant. Temperature dependence of the Cu diffusion coefficient is described with the aid of the Arrhenius relation D?=?3.75?×?10^?3 exp (?1.15?±?0.10?eV/k _B T) and the corresponding activation energy of copper in MgB₂ system is found to be about 1.15?eV. The possible reasons for the observed improvement in microstructural and superconducting properties of the samples due to Cu diffusion are also discussed.     

Diffusion of copper in thin TiN films

The diffusivity of copper in thin TiN layers was determined in specimens prepared by r.f. sputtering a copper (80 nm) layer onto a TiN (200 nm) layer on sapphire and silicon substrates. Specimens were isothermally heat treated at 608, 635 and 700 °C at pressures lower than 2 × 10^?6 Pa; they were compositionally analyzed by Rutherford backscattering spectroscopy and Auger sputter profiling; and they were microstructurally characterized by transmission electron microscopy and electron diffraction. The diffusivity D = 9 × 10⁷cm²s^?1exp(?427 kJmol^?1/RT) from 608 to 700 °C. The mechanisms of copper diffusion were not bulk processes, but they were probably processes involving primarily grain boundaries in the TiN. This very low diffusivity at these temperatures makes TiN/Cu an excellent candidate for a high temperature metallization for silicon solar concentrator cells.     

Mechanical properties of and cracks and wrinkles in vacuum-deposited MgF2, carbon and baron coatings

The mechanical properties of coatings of MgF₂, carbon and boron were investigated. The internal stress in the MgF₂ coatings on glass substrates, measured by the cantilever method, was tensile and was about 4×10⁹dyncm^?2, while those of carbon and boron were compressive and were about 7×10⁹dyncm^?2 and 2×10⁹dyncm^?2 respectively. Young's moduli of MgF₂ and carbon were determined by the vibrating reed method to be 15×10¹¹dyncm^?2 and 2×10¹¹dyncm^?2 respectively. Cracks were observed in sufficiently thick MgF₂ coatings on glass substrates and the adhesion energy was estimated to be 270 erg cm^?2 from the measured values of the internal stress, Young's modulus and crack initiation thickness. Wrinkles were generated under certain conditions in carbon and boron coatings. It was found that exposure of the coatings to the atmosphere was essential to the initiation of the wrinkles.     

Diffusion of promethium in silicon

The first investigations have been made on the diffusion of promethium in silicon. In the temperature range from 1100 to 1250 °C the diffusion constant of promethium increases from ∼1×10⁻¹³ cm²/s to ∼1.5×10⁻¹² cm²/s. The temperature dependence of the diffusion coefficient can be described by D = 5 x 10⁻¹ exp[-(3.3 eV/kT]cm²/s. Pis’ma Zh. Tekh. Fiz. 23, 46–50 (January 26, 1997)     

Effect of inter-electrode spacing on structural and electrical properties of RF sputtered AlN films

An attempt has been made to correlate the morphological and electrical properties of RF sputtered aluminum nitride (AlN), with target to substrate distance (D _ts) in sputter chamber. AlN films, having thickness around 3,000 Å, were deposited on silicon substrates with different D _ts values varying from 5 to 8 cm. XRD results indicated that the crystallinity of c-axis oriented films increase significantly with decrease in D _ts and the FTIR absorption band of the films became prominent at shorter D _ts. The surface roughness increased from 1.85 to 2.45 nm with that in D _ts. A smooth surface with smaller grains was found at shorter D _ts. The capacitance–voltage (C–V) measurements revealed that the insulator charge density (Q _in) increased from 3.3 × 10¹¹  to 7.3 × 10¹¹ cm^?2 and the interface state density (D _it) from 1.5 × 10¹¹  to 7.3 × 10¹¹ eV^?1cm^?2 with the increase in D _ts.     

Samarium diffusion in polycrystalline samarium sulfide

The diffusion of samarium in polycrystalline samarium sulfide with a superstoichiometric composition of Sm_1.13S has been studied at T = 1000 and 1100°C. It is concluded that Sm atoms predominantly migrate over the boundaries of monocrystalline domains of the polycrystalline sample. The diffusion coefficient varies within D ≈ 10⁻²−10⁻³ cm²/s. In the temperature dependence of the diffusion coefficient, the diffusion activation energy is evaluated at E ∼ 4.6 eV and the preexponential term at D ₀ ≈ 1.8 × 10¹⁵ cm²/s.     

Preface

The diffusion of platinum and gold in nickel at relatively low temperatures (250–725 °C) was measured by Rutherford backscattering spectrometry (RBS). The diffusion profile of the noble metal in nickel was calculated from RBS spectra. This method takes fully into account the dependence of the energy losses of the backscattered particle along the inward and outward paths on the changing energy of the particle and the changing composition of the target. Diffusion coefficients are calculated from the measured diffusion profile. The dependence of the diffusion coefficient on temperature obeys the Arrhenius law. The activation enthalpies are 78.2 kJ mol^-1 and 119.6 kJ mol^-1 for the diffusion of platinum and gold respectively into nickel. The frequency factors are respectively 2.6 × 10^?9cm²s^?1 and 1.4 × 10^?7cm²s^?1. Experimental data suggest that diffusion along the grain boundaries is 2–3 times as fast as bulk diffusion.     

The effect of beta radiation on Si-I → Si-II phase transformations in silicon under an indenter

The phase transition from a diamond-like crystalline lattice of the Si-I phase to the β-tin type structure of the Si-II phase has been studied by measuring electric resistance under an indenter incorporated into a narrow (d ≈ 2 μm) crevice between metal contacts. It was established that the relative volume fraction of the metalized Si-II phase formed during indentation decreases under the action of a low dose (fluence F = 3.24 × 10¹⁰ cm^?2) of low-intensity (I = 1.8 × 10⁵ cm^?2 s^?1) beta radiation.     

Thermodynamic and mass transport properties of “LiIn”

The EMF of the vario-stoichiometric phase “LiIn” lies between 497 and 145 mV relative to pure lithium at 415°C over the composition range from 46.7 to 63.3 a/o Li, corresponding to a lithium activity varying from 2.29×10^?4 to 8.67×10^?2 at that temperature. On the Li-deficient side of LiIn, the chemical diffusion coefficient increases rapidly with decreasing lithium concentration, approaching the value of 3.98×10^?5 cm²/sec near the In-rich phase boundary of “LiIn”. In the region of positive deviations from the ideal stoichiometry, the chemical diffusion coefficient remains essentially constant up to a composition about 57.8 a/o Li. At higher lithium concentrations, the chemical diffusion coefficient first decreases and then increases as more lithium is added to the sample, and shows a minimum value of 4.73×10^?7 cm²/sec at 62.2 a/o Li.     

Low temperature interdiffusion in the Au-Pd and Au-Rh thin film couples

Interdiffusion profiles in thin polycrystalline multilayer films of Pd-Au and Ti-Rh-Au at temperatures up to 490°C have been measured by Rutherford backscattering. Room temperature grain boundary diffusion of Au into Rh was observed and analyzed to give D_B = 3.5 × 10^-17 cm² sec^-1. The Whipple analysis is applied to our data for the diffusion of Au in Pd; using the lattice diffusivity of Neukam, an activation energy for grain boundary diffusion of 0.9 eV is found. The diffusion of Pd in Au has also been analyzed using the Whipple model, which gives a grain boundary activation energy of 0.6 eV.     

The temperature dependence of stresses in aluminum films on oxidized silicon substrates

In situ measurements were carried out of stress at the AlSiO₂ interface at various temperatures (25–500 °C) and for various film thicknesses (0.2–1.6 microm). These data are complemented with microstructural studies by transmission electron microscopy.For the aluminum films studied, the intrinsic structural component was very small (less than 2 × 10⁸ dyn cm^?2). On heating, thermal mismatch led to a compressive stress, with dσ/dT ≈ ?2 × 10⁷ dyn cm^?2 °C; these films yielded at 6σ6 ; ? 5 × 10⁸ dyn cm^?2, primarily through diffusion creep and grain growth. On cooling from about 450–500 °C, thermal mismatch led to a tensile stress which was limited mainly by dislocation slip. The final room temperature value after thermal cycling ranged from 0.5 × 10⁹ dyn cm^?2 for a 1.5 microm film to 8 × 10⁹ dyn cm^?2 for a 0.2 microm film; these values are believed to represent the critical stress for the generation of dislocation loops within the grains.The grain size of cold-deposited aluminum films ranged from about 0.2 microm for films 0.45 microm thick to about 2 microm for films 1.5 microm thick. Thermal cycling led to an order-of-magnitude increase in the grain size together with the formation of dislocation networks within the grains.     

On the Evaporation of C60 in Vacuum and Inert Gases at Temperatures Between 830 K and 1050 K

Abstract

The binary diffusion coefficient D_AB of subliming C₆₀ in He, N₂ and Ar gas has been determined at a gas pressure between 5 and 10 kPa. It resulted D_AB/(cm^2/s)=D_o(P_o/P_t(T/T_o)ⁿ as a function of the total pressure P_t of the vapor phase and temperature T. At T_o=273 K and P_o=1.0133×10⁵ P_a, the values D_o = (0.059±0.004) cm²/s, (0.011±0.003) cm²/s, (0.012±0.007) cm²/s, n = 1.77±0.06, 2.02±0.18, 1.77±0.37 were obtained for He, N₂, Ar and (830-1000) K, (800-1020) K, (875-1095) K, respectively. Only 40 wt% of the initial C₆₀ material yielded reliable D_AB where the vapor pressure of C₆₀ followed log₁₀(P/Pa) = -(8976±60)/T/K+(11.05±0.07) for T between 640 and 1055 K.     

Low temperature interdiffusion in Cu/Ni thin films

Interdiffusion in Cu/Ni thin films was studied by means of Auger electron spectroscopy in conjunction with Ar⁺ ion sputter profiling. The experimental conditions used aimed at simulating those of typical chip-packaging fabrication processes. The Cu/Ni couple (from 10 μm to 60 nm thick) was produced by sequential vapor deposition on fused-silica substrates at 360, 280 and 25 °C in 10^-6 Torr vacuum. Diffusion anneals were performed between 280 and 405 °C for times up to 20 min. Such conditions define grain boundary diffusion in the regimes of B- and C-type kinetics. The data were analyzed according to the Whipple-Suzuoka model. Some deviations from the assumptions of this model, as occurred in the present study, are discussed but cannot fully account for the typical data scatter. The grain boundary diffusion coefficients were determined (for nickel through copper, Q_b = 33.7 kcal mol^-1 (1.46 eV), D_b⁰ = 4.2 × 10^-2 cm²s^-1; for copper through nickel, Q_b = 30.2 kcal mol^-1 (1.3 eV), D_b⁰ = 7.6 × 10^-5 cm²s^-1) allowing calculation of respective permeation distances.     

Sorption properties of rocks on the territory of the former Semipalatinsk test site

The ability of granite and diorite, which are the most abundant rocks on the territory of the Semipalatinsk test site, to take up ¹³⁷Cs and ⁹⁰Sr present in tunnel waters of the Degelen mountain massif was studied in a laboratory. Experiments were performed both with simulated solutions and with real radioactive groundwater. The ¹³⁷Cs distribution coefficients were found for samples of typical granites, albitized granite, quartz porphyry, and diorite from the former Semipalatinsk test site. The ¹³⁷Cs distribution coefficient K _D (cm³ g^?1) was found to be n × 10³–n × 10⁴ for albitized granite, 60–80 for quartz porphyry, and 30–50 for granite. The ability of quartz porphyry and granite to take up ⁹⁰Sr from simulated solutions is characterized by the distribution coefficients K _D = 10–20 cm³ g^?1, and that of albitized granite, by K _D = 110?120 cm³ g^?1. The data obtained are required for predicting the migration of long-lived fission products from the nuclear explosion with underground waters from central zones of underground nuclear explosions in the former Semipalatinsk test site and for calculating the mass transfer in specific geologic media.