Local structure changes of Cu55 cluster during heating

The structural relaxation of a cluster containing 55 atoms at elevated temperatures is simulated by molecular dynamics. The interatomic interactions are given by using the embedded atom method （EAM） potential. By decomposing the peaks of the radial distribution functions （RDFs） according to the pair analysis technique, the local structural patterns are identified for this cluster. During increasing temperature, structural changes of different shells determined by atom density profiles result in an abrupt increase in internal energy. The simulations show how local structural changes can strongly cause internal energy to change accordingly.     

”Reverse” annealing mechanism in ion-doped silicon layers subjected to electron beam heating

The annealing of silicon layers doped by high doses (10¹⁵-10¹⁶ cm^–2) of P⁺, As⁺, or Sb⁺ ions by means of an electron beam applied for 10–20 sec is studied. It is established that when a certain specimen temperature is exceeded, reverse annealing of the ion-implanted layers commences- a decrease in the degree of activation of the impurity introduced. The mechanism of reverse annealing in Si+> and Si+> layers is related to exit of P⁺ and As⁺ ions into interstices with their subsequent sublimation. In the case of heating of an Si+> layer reverse annealing is caused by exit of Sb⁺ ions into interstices and formation of impurity-defect complexes.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 97–102, August, 1989.     

Color changes in wood during heating: kinetic analysis by applying a time-temperature superposition method

This paper deals with the kinetics of the color properties of hinoki (Chamaecyparis obtusa Endl.) wood. Specimens cut from the wood were heated at 90–180°C as accelerated aging treatment. The specimens completely dried and heated in the presence of oxygen allowed us to evaluate the effects of thermal oxidation on wood color change. Color properties measured by a spectrophotometer showed similar behavior irrespective of the treatment temperature with each time scale. Kinetic analysis using the time-temperature superposition principle, which uses the whole data set, was successfully applied to the color changes. The calculated values of the apparent activation energy in terms of L ^*, a ^*, b ^*, and DE^*_abDelta E^{*}_{ab} were 117, 95, 114, and 113 kJ/mol, respectively, which are similar to the values of the literature obtained for other properties such as the physical and mechanical properties of wood.     

Multistage radiation-stimulated changes in the microhardness of silicon single crystals exposed to low-intensity β irradiation

Radiation-stimulated and postradiation changes in the microhardness of silicon single crystals exposed to irradiation with a low-intensity flux of β particles (I = 9 × 10⁵ cm^?2 s^?1, W = 0.20 + 0.93 MeV) are studied. It is established that the inversion of the radiation-induced plastic effect occurs at a characteristic irradiation time τ_c = 75 min; i.e., irradiation of silicon single crystals for a time τ < τ_c leads to nonmonotonic reversible hardening, whereas nonmonotonic reversible softening is observed under irradiation for a time τ > τ_c. It is demonstrated that there exists a correlation between the nonmonotonic dependences of the microhardness and the concentration of electrically active defects at acceptor levels with energies E _c ? 0.11 eV, E _c ? 0.13 eV, and E _c ? 0.18 eV on the irradiation time.     

Effect of the low-temperature (20–60°C) heating of silicon on its microhardness

Changes in the microhardness of silicon samples exposed to temperatures of 20–60°C are studied. It is found that the microhardness increases; this effect is preserved at room temperature for 20 min and non-monotonically depends on the temperature and exposure time (the changes are maximal at ～40°C and ～100 s, respectively). The microhardness of samples with native oxide removed does not change. The results are discussed in terms of a model of processes in the silicon-oxide system, which was previously proposed for the case of irradiation of silicon with light. The practical importance of the effect is discussed.     

Electrically stimulated movement of edge dislocations in silicon in the temperature range 300–450 K

The movement of edge dislocations and the related acoustic emission of Si (111) carrying a direct current of density 0.5?5×10⁵ A/m² in the [110] direction are studied in the temperature range T=300–450 K. It is shown that the basic mechanism of dislocation movement is the electric wind determining the magnitude of the effective charge (per atom of the dislocation line) Z _eff=0.06 (n-Si) and ?0.01 (p-Si). Matching theory with experimental data has made it possible to determine the main contribution of edge dislocations to the acoustic-emission response of the silicon samples under investigation. The characteristic transition frequencies of dislocations in n-and p-Si from one metastable state into another are found to be f _max=0.1–0.5 Hz. The numerical values of the diffusion coefficient for atoms in the dislocation impurity atmosphere are estimated as 3.2×10^?18 m²/s (n-Si) and 1.5×10^?18 m²/s (p-Si).     

Structure modifications in AS+−ION implanted silicon layers during pulse thermal treatment

Abstract

The silicon layers structure after As⁺?ion implantation and subsequent pulse annealings, which were carried out in nanosecond (Q-switched ruby laser) or/and few seconds (halogen lamps) time intervals, has been studied by transmission electron microscopy techniques. It has been shawn that the structure state is determined to a large extend by pulse annealing parameters. In the case of second pulse annealing the level of ion-implanted layer disordering affects considerably the obtained structure.     

Energy transport in silicon–aluminum composite thin film during laser short-pulse irradiation

Energy transport in silicon–aluminum composite thin films due to short-pulse laser irradiation is examined. Frequency dependent phonon transport in the silicon film is considered to formulate equivalent equilibrium temperature while modified two-equation model is used in the aluminum film to obtain electron and phonon temperatures. Thermal boundary resistance across the films is incorporated in the analysis. Transmittance, reflectance, and absorption of the incident laser beam are determined using the transfer matrix method. Equivalent equilibrium temperatures resulted from frequency dependent and frequency independent solutions are compared. It is found that phonon temperature increase at the aluminum interface is suppressed by phonon transport to the silicon film, which is more pronounced at low laser pulse intensities. The influence of the ballistic phonons on equivalent equilibrium temperature in the silicon film is found to be significant.     

Low-frequency dielectric properties of yttrium formate crystallohydrate upon heating after quenching to −60°C

The specific features of the dielectric characteristics of yttrium formate crystallohydrate are studied. Its frequency dependences of dielectric permittivity and conductivity are obtained and analyzed in the 10⁻¹–10⁶ Hz range. Anomalies in the narrow temperature intervals of the dielectric properties of yttrium formate crystallohydrate are noted. The activation energies of relaxation processes are calculated from the experimental data. It is assumed that such anomalies are caused by changes in the dynamics of protons that participate in hydrogen bonds in the crystal structure.     

Electric-field mediated nickel-induced nanocrystallization of?amorphous silicon thin films in the complete absence of external heating

DC electric-field mediated nanocrystallization of thermally evaporated silicon thin films with nickel as seed/cap layer has been attempted in complete absence of any external heat input. When 60 nm Si thin film coated onto 5 nm Ni thin film was treated by a direct current (DC) electric field (up to 3.3 kV/cm up to 5 minutes) after the deposition, amorphous silicon thin films became nanocrystalline (6–10 nm). Silicon nanograins (average diameter 90 nm) grow to larger sizes (average diameter 240 nm) with sharpening of grain size distribution. Huge grain growth (4-fold increase) has been observed when nickel was used as cap layer (5 nm Ni/60 nm Si). XRD data show the signature of nickel silicide formation on the surface in nickel cap layer case. Field treatment has changed the optical absorption edge (shifts left in nm units) and the refractive index of silicon thin film when nickel was used as under layer, and an almost negligible effect on the optical properties has been observed when nickel was used as cap layer.     

Structural changes in austenitic steel in contact with solid oxide electrolyte at 950°C

Changes in the structure and redistribution of alloying elements in 10Kh23N18 austenitic steel after operating at 950°C for 8800 h in contact with La-Sr-Mn-O electrolyte are investigated to establish the reasons for the degrading of the surface layer of a current collector in a solid-oxide fuel cell over long periods of service. It is established that the degradation of the surface layer of steel is associated with the formation of a network of silicon and aluminum oxides along grain boundaries and the considerable discrepancy between the linear thermal expansion coefficients of steel and the solid electrolyte.     

The Mössbauer spectroscopy studies of matrix changes during continuous heating from as-quenched state of high carbon tool steel

Helium is unique in the sense that about 3% of low-energy antiprotons stopped in it survive with an average lifetime of a few microseconds, forming metastable states of the exotic antiprotonic helium atom ( $\overline{p}$ -He^?+?+?-e^??). This lifetime is sufficient to carry out laser spectroscopy measurements of atomic transitions of this exotic atom. The antiproton-to-electron mass ratio $M_{\overline{p}}/m_e$ can be deduced from comparisons with three-body QED calculations. A systematic study of the energy levels of this exotic atom started soon after its discovery, continuously aiming for higher precision (for a review see Yamazaki et al., Phys Rep 366:183, (2002) and references therein). Recently, at the Antiproton Decelerator of CERN, a femtosecond optical frequency comb and continuous-wave pulse-amplified laser were used to measure 12 transition frequencies to fractional precisions of (9???16)×10^???9, yielding an antiproton-to-electron mass ratio of 1836.152674(5).     

Controlling the transmission of ultrahigh frequency bulk acoustic waves in silicon by 45° mirrors

In this paper, we present a feasible microsystem in which the direction of localized ultrahigh frequency (∼1 GHz) bulk acoustic wave can be controlled in a silicon wafer. Deep etching technology on the silicon wafer makes it possible to achieve high aspect ratio etching patterns which can be used to control bulk acoustic wave to transmit in the directions parallel to the surface of the silicon wafer. Passive 45° mirror planes obtained by wet chemical etching were employed to reflect the bulk acoustic wave. Zinc oxide (ZnO) thin film transducers were deposited by radio frequency sputtering with a thickness of about 1 μm on the other side of the wafer, which act as emitter/receptor after aligned with the mirrors. Two opponent vertical mirrors were inserted between the 45° mirrors to guide the transmission of the acoustic waves. The propagation of the bulk acoustic wave was studied with simulations and the characterization of S₂₁ scattering parameters, indicating that the mirrors were efficient to guide bulk acoustic waves in the silicon wafer.     

Rapid nickel diffusion in cold-worked carbon steel at 320–450 °C

The diffusion coefficient of nickel in cold-worked carbon steel was determined with the diffusion couple method in the temperature range between 320 and 450 °C. Diffusion couple was prepared by electro-less nickel plating on the surface of a 20% cold-worked carbon steel. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time to 12,000 h. The diffusion coefficient (D_Ni) of nickel in cold-worked carbon steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 0% of nickel. The temperature dependence of D_Ni is expressed by D_Ni = (4.5 + 5.7/?2.5) × 10^?11 exp (?146 ± 4 kJ mol^?1/RT) m²s^?1. The value of D_Ni at 320 °C is four orders of magnitude higher than the lattice diffusion coefficient of nickel in iron. The activation energy 146 kJ mol^?1 is 54% of the activation energy 270.4 kJ mol^?1 for lattice diffusion of nickel in the ferromagnetic state iron.     

IR spectroscopy of structural changes of α-chymotrypsin related to the changes of function in organic solvents

To determine the variations in the secondary structure of α-chymotrypsin related to changes of function, we measure the ATR-FTIR spectra of the lyophilized enzyme, its solutions in normal and heavy water, tablets wetted in acetonitrile and cyclohexane, and suspensions in these solvents. The experimental results show that the most significant structural changes (a decrease in the content of α-helical fragments and an increase in the content of β-sheets) are related to the transition from the aqueous solution to the lyophilized sample. Similar but less developed structural changes are observed for the transition from the lyophilized sample to suspensions in organic solvents.     

Thermal expansion and phase changes of 16Kh12V2FTaR steel in temperature range from 20 to 1000 °C

The article presents the results of investigation of thermal expansion of 16Kh12V2FTaR steel in the temperature range 20–1000 °C. Measurements were carried out by dilatometric method with the error (1.5–2)×10^?7 K^?1. The temperature dependences of thermal coefficient of linear expansion of steel have been obtained in ferrite-martensite and ferrite-perlite states, and reference tables have been calculated. Influence of samples cooling rate on martensite phase formation is shown.     

Do oxygen molecules contribute to oxygen diffusion and thermal donor formation in silicon?

In- and out-diffusion experiments of oxygen in silicon indicate the existence of an oxygen-containing species diffusing much faster than interstitial oxygen at temperatures below about 700°C. The formation of oxygen-related thermal donors in the temperature range around 450°C also requires a fast diffusing species. The paper examines the possibility of this fast diffusing species beingmolecular oxygen, as had been suggested earlier. Special emphasis will be placed on experimental results which have become available since that time. These results allow one to relate thermal donor formation to the loss of interstitial oxygen and to oxygen precipitation. The role of carbon is also considered in this context.Paper submitted as contribution to special issue on Molecule-Like Defects in Crystalline Semiconductors. Appl. Phys. 48/1 January 1989     

A Geometric Approach to Boundaries and Surface Defects in Dijkgraaf–Witten Theories

Dijkgraaf–Witten theories are extended three-dimensional topological field theories of Turaev–Viro type. They can be constructed geometrically from categories of bundles via linearization. Boundaries and surface defects or interfaces in quantum field theories are of interest in various applications and provide structural insight. We perform a geometric study of boundary conditions and surface defects in Dijkgraaf–Witten theories. A crucial tool is the linearization of categories of relative bundles. We present the categories of generalized Wilson lines produced by such a linearization procedure. We establish that they agree with the Wilson line categories that are predicted by the general formalism for boundary conditions and surface defects in three-dimensional topological field theories that has been developed in Fuchs et al. (Commun Math Phys 321:543–575, 2013)