Crystallization over the liquid layer

In this article, a new phenomenon of high-speed crystallization of metals in a low-temperature plasma formed as a result of the effect of a short laser pulse is considered. The mechanism of the way the reaction occurs on the surface of the melt formed under the effect of the laser pulse on an amorphous substrate is described. The main factors affecting the crystallization process are described. Primary attention is paid to laminar convection and the latent heat of crystallization.     

Analysis of the vibroacoustic field in an extended layer and in the layer–semispace structure

We analyze the acoustic field excited by dipole vibration sources in an extended layer. Two formulations of the problem are considered. In the first case, it is assumed that the layer boundaries are stiff in the normal direction, but the particles oscillating at the boundary may slip in the direction tangential to the walls. In another case, a rigid contact of a “patch” type takes place at the boundary with the host medium. A pattern of the space distribution of the field amplitude both inside and outside the layer is given. The vibration field of the sources operated in pulsed mode in the wave hodograph plane is presented. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 2, pp. 151–163, February 2009.     

Dynamics of the cadmium-chloride-type layer structures

A linear chain model with intralayer force constants has been used to interpret the long wavelength lattice vibrations of the layer structures - CdBr₂, CdCl₂, MnCl₂ and CoCl₂. In the nearest neighbour approximation this model gives results in agreement with experimental information for MnCl₂ and CoCl₂; the discrepancy in the case of CdBr₂ and CdCl₂ is explained by including the effect of the second nearest neighbour, which would be present because of long range electrostatic forces in these cases.     

Viscous layer at the ice surface

We analysed the isothermal relaxation of the strain stored in strain gauge as a consequence of the fast cooling of an ice sample on which it was previously frozen. This enabled an evaluation of the activation energy of the ice surface viscosity, indicating that the vacancy migration is probably responsible for this phenomenon.     

Inversion layer resistance in silicon inversion layer solar cells

The inversion layer resistance is very important for metal-insulator-semiconductor inversion layer (MIS/IL) solar cells, and usually it is the main part of the series resistance. It is found that the inversion layer resistance and the junction depth are determined by the operating voltage for an MIS/IL solar cell. On the basis of MIS theory, a general relationship between the operating voltage and the inversion layer resistance (and the junction depth) has been investigated. Practical computations have been done for MIS/IL solar cells with a silicon nitride insulator layer. It is found that the inversion layer resistance has a minimum value for operating voltage near 0.4 V, and the junction depth decreases monotonically with the increase of the operating voltage.     

On the effect of acoustic layer modes in an MOS oxide on inversion layer mobility

The effect of thermally generated acoustic layer modes in the silicon dioxide gate of a silicon MOSFET on inversion layer electron mobility is investigated using the deformation potential formalism. The layer mode contribution to mobility is found to vary significantly for SiO₂ layer thicknesses less than about 25 nm above which an asymptotic “thick” layer value is approached. This “thick” layer value differs considerably from the contribution in the limit of a zero thickness layer and, for some conduction band minima and especially for higher electron energies, can be quite large, even dominating over other phonon contributions. However, the overall contribution appears to be small and thus likely not the source of the discrepancy between theoretical and experimental mobility values     

层层递进,妙趣横生——谈物理大师费恩曼的教学风格

以《费曼物理学讲义》中"量子行为"一章为例,研究费恩曼的物理教学风格;指出费恩曼"量子行为"的教学体现了层层递进,渐入佳境的教学特点.     

Titanium and aluminum nitride synthesis via layer by layer LA-CVD

The possibility of the layer-by-layer synthesis of 3D parts from nitrides of titanium or aluminum by selective laser sintering/melting is discussed. The relationship between laser processing parameters and structure and phase content of sintered/melted samples are studied by means of optical metallography, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Optimal parameters of SLM process for AlN and TiN synthesis are determined. Solid 3D parts containing a TiN phase are produced from Ti powder. Distortion of the crystalline lattice of AlN and TiN phases is observed with the laser energy input.     

The charge storage of the nc—Si layer

Sandwiched structures (a-SiN_x/a-Si/a-SiN_x) have been fabricated by the plasma enhanced chemical vapour deposition technique. A Si nanocrystal (nc-Si) layer was formed by crystallization of an a-Si layer according to the constrained crystallization principle after quasi-static thermal annealing at 1100℃ for 30 min. Transmission electron microscopy (TEM) and Raman scattering spectroscopy clearly demonstrated that nc-Si grains were formed in the as-deposited a-Si layer after annealing. The density of nc-Si grains is about 10¹¹cm^-2 as shown by TEM photographs. Using capacitance－voltage (C－V) measurements we investigated the electrical characteristics of the sandwiched structures. The charge storage phenomenon of the nc-Si layer was observed from the shift of flat-band voltage (V_FB) in C－V curves at a high frequency (1 MHz). We estimated the density of nc-Si grains to be about 10¹¹cm^-2 from the shift value of V_FB, which is in agreement with the result of TEM photographs. At the same time, we found that the shift of V_FB increased with the increase of the applied constant dc voltage or the thickness of the nc-Si layer.     

Near-surface turbulence in the atmospheric boundary layer

Measurements of the near-surface turbulence in the atmospheric boundary layer have been made using hot-wire probes above the salt flats of northwestern Utah, where the momentum thickness Reynolds number, R_θ, is O(10⁶), and the surface is smooth and nearly devoid of flow obstructions. The measurements were made with arrays of up to 24 parallel straight sensors and with a modular 12-sensor probe capable of measuring all of the components of the instantaneous velocity vector and velocity gradient tensor. Measurements were also made in a laboratory wind tunnel at R_θ=1730 using 22 straight sensors. The data analysis focuses on the effects of the Reynolds number on turbulence properties and on the physics of the dissipation rate of turbulent kinetic energy.Some properties are found to be dependent on the Reynolds number when normalized with inner variables, while others are not. Among those that show the significant Reynolds number dependence are the rms and the skewness factor of the streamwise velocity fluctuations.Significant differences in flow structure, particularly those related to high rates of dissipation, are implied by the data. The joint PDF and covariance integrand of streamwise and wall normal vorticity fluctuations show less preferred orientation of the vorticity vector in the buffer layer at R_θ of O(10⁶) than at R_θ=1070. The largest contribution to the dissipation rate, at O(10⁶) is by the ∂w/∂z velocity gradient, while this term makes a quite small contribution to the dissipation rate at low R_θ. Here w and z are the spanwise velocity fluctuations and direction, respectively. Conditional analysis in the streamwise-wall normal (x−y) plane based on high instantaneous dissipation rate shows that the typical high dissipation rate events are generally similar at high and low Reynolds numbers, but display some significant differences.     

Brillouin scattering in the layer compound GaSe

Brillouin scattering has been used to obtain the five independent elastic constants in the layer compound GaSe. The results show clear elastic anisotropy of the crystal. Resonant Brillouin scattering near the absorption edge has also been studied, but no resonant enhancement was found.     

Temperature dependence of the Stranski-Krastanov layer thickness

Thin films grow on a substrate in one of three possible growth modes: Laminar (Frank-van der Merwe mode), as islands (Volmer-Weber mode) or as islands on top of a few laminar layers (Stranski-Krastanov (SK) mode). The thickness of the laminar layer in SK-mode, Θ_SK, is a materials constant, dependent only on the physical properties of the substrate-film interface. We show, using scanning Auger/electron microscopy, that Θ_SK has a specific temperature dependence, in excellent quantitative agreement with theoretical prediction (M. Zinke-Allmang et al., Surf. Sci. 200 (1988) L427). For Si(100)/Ge Θ_SK increases about 3 × 10⁻⁴ monolayers/K with increasing temperature in the range 400–900 K. The change is completely reversible and due to the existence of the islands on top of the SK-layer.     

Electronic properties of the layer semiconductor InSe

The three-dimensional band structure of InSe is calculated by the tight-binding and pseudopotential methods. The two band structures have many features in common and both agree with most optical and photoemission data. The high ionicity of this compound is reflected in the low dispersion of the energy bands and is evidenced by a calculation of the total valence charge density.     

Optical properties of the layer compound GaTe

The optical constants of layer compound GaTe have been obtained in the energy range 1.0 to 6.0 eV from near normal incidence reflectivity spectrum. Data have been processed to yield the real and imaginary parts of the refraction index and of the dielectric constant. Band parameters have been also empirically estimated.     

Two-dimensional magnetoplasmon in the silicon inversion layer

The influence of a magnetic field on the behavior of the two-dimensional plasmon is studied in the n-inversion layer of p-type silicon at fixed wavevector as a function of electron density and magnetic field. Most of the behavior is well described by a dispersion relation and lineshape based on a classical theory of the electron gas. However, deviations from the theory are observed which may indicate an interaction with other modes of the system.     

Light-induced layer by layer thickening in photosensitive liquid crystal membranes

Photosensitive smectic membranes of pure liquid crystal (LC) were studied under white light illumination. A thickness increase is observed in the illuminated film area. Appropriate light and thermal conditions lead to a thickening layer by layer process. This unusual phenomenon is opposite to the well-known step-by-step thinning transitions under heating. We give a phenomenological interpretation for thickening based on layer transport of LC matter towards the illuminated area.     

On hydrodynamic instability of the ozone layer

We show that instability may be arisen when the large-scale waves propagate in the ozone layer of Earth's atmosphere. The instability criterion suitable both for the acoustic waves and for the Rossby waves is found. Moreover, the possibility of the spatially located dissipative Rossby vortical structures formation in this layer is established.     

Temporal variability of the telluric sodium layer

The temporal variability of the telluric sodium layer is investigated by analyzing 28 nights of data obtained with the Colorado State University LIDAR experiment. The mean height power spectrum of the sodium layer was found to be well fitted by a power law over the observed range of frequencies, 10 microHz to 4 mHz. The best-fitting power law was found be be 10(beta)nu(alpha), with alpha=-1.79+/-0.02 and beta=1.12+/-0.40. Applications to wavefront sensing require knowledge of the behavior of the sodium layer at kilohertz frequencies. Direct measurements at these frequencies do not exist. Extrapolation from low-frequency behavior to high frequencies suggests that this variability may be a significant source of error for laser guide star adaptive optics in large-aperture telescopes.