Growth and structure of WC/Si multilayer x-ray mirror

WC/Si multilayer X-ray mirrors (MXMs) with nominal layers thicknesses of 0.2…30.3 nm (periods: 0.7…38.9 nm) were deposited by direct current magnetron sputtering and studied by X-ray diffraction and cross-sectional transmission electron microscopy (TEM). Carbide and silicon layers are amorphous throughout the studied thickness range. The WC layers interact with Si layers with formation of tungsten silicides (WSi₂, W₅Si₃) and silicon carbide in as-deposited state. The bottom interlayer (WC-on-Si) consists of two subzones of approximately equal thickness. An estimation of the thickness, density, and composition of all layers is made. Based on the experimental data, a five-layer model of the WC/Si MXM structure is suggested.Методами рентгенівської дифракції та просвічувальної електронної мікроскопії досліджені багатошарові рентгенівські дзеркала (БРД) WC/Si, що виготовлені методом прямоточного магнетронного розпилення з фіксованими швидкостями осадження з номінальними товщинами шарів у діапазоні 0,2…30,3 нм (періоди 0,7…38,9 нм). У всьому діапазоні досліджуваних товщин шари WC та Si являються аморфними. Шари WC та Si взаємодіють з утворенням силіцидів вольфраму (WSi₂, W₅Si₃) та карбіду кремнію в початковому стані. Нижня перемішана зона складається з двох перемішаних підзон приблизно рівної товщини. Зроблена оцінка товщини, щільності та складу всіх шарів. Спираючись на експериментальні результати запропонована п’ятишарова модель будови БРД WC/Si.Методами рентгеновской дифракции и просвечивающей электронной микроскопии исследованы особенности роста многослойных рентгеновских зеркал (МРЗ) WC/Si, изготовленных методом прямоточного магнетронного распыления с номинальными толщинами слоев в диапазоне 0,2…30,3 нм (периоды 0,7…38,9 нм). Во всем диапазоне исследуемых толщин слои WC и Si находятся в аморфном состоянии. Установлено взаимодействие слоев WC и Si с образованием силицидов вольфрама (WSi₂, W₅Si₃) и карбида кремния в исходном состоянии. Нижняя перемешанная зона состоит из двух подзон примерно равной толщины. Сделана оценка толщины, плотности и состава всех слоев. На основе определенных параметров предложена пятислойная модель строения МРЗ WC/Si

Phase-structural and non-linear effects in heterogeneous systems

This theme issue is concerned with modern achievements in the theory, computational and experimental studies of the phase transitions that occur in heterogeneous systems. The papers are divided into six thematic sections devoted to patterned formations, transport and magnetic phenomena, hydrodynamic flows as well as biological applications. Special attention is paid to various non-linear effects met in these processes and leading to some unexpected at first glance physical aspects

Towards a theory of magnetic hyperthermia: effect of immobilized chain-like aggregates

We present results of theoretical approach and mathematical modeling of magnetic hyperthermia produced by aggregates of ferromagnetic nanoparticles immobilized in a non-liquid carrier medium. It is supposed that the particles, due to their magnetic either disperse interaction, can form linear chain-like clusters. The mathematical model of kinetics of the particles remagnetization is formulated and solved for the cases of the single particles as well as for two- and three-particles chains. The limiting cases of the strong and weak internal magnetic anisotropy of the nanoparticles are considered. The results show that the chain-like aggregates reduce the heat production in the case of the strong magnetic anisotropy of the particles and enhances that in the opposite case of the weak anisotropy

Magnetic hyperthermia in a system of dense cluster of ferromagnetic nanoparticles

This article deals with mathematical modeling and theoretical study of the magnetic hyperthermia in a system of single-domain ferromagnetic nanoparticles immobilized in a carrier medium and united in dense clusters. The system is placed in an oscillating magnetic field. The results show that the magnetic nanoparticles clustering weakens the hyperthermia effect

To the theory of magnetic hyperthermia in viscoelastic media: effect of interparticle interaction

We propose a theoretical model of magnetic hyperthermia produced by a system of single-domain ferromagnetic particles in elasto-viscous and rigid media. Both mechanisms of the energy absorption, the internal remagnetization of the particles and their rotation under the field action are taken into account. Effects of magnetic interparticle interaction are in focus of our attention. Our analysis shows that the interaction can significantly enhance the heat production. The thermal effects in the elasto-viscous and rigid media are compared

Domain structures in thin layers of a ferrocolloid

We consider the problem of formation of structures composed of identical domains in a ferrocolloid that fills a space between two closely situated parallel planes under action of a normal external magnetic field. Those structures begin to arise under conditions favouring the phase separation of the ferrocolloid. An inhomogeneous system including two equivalent colloidal phases would ultimately evolve due to Ostwald ripening, but for a scaling effect of the planes that stops the evolution at a certain level and makes for the resulting domain structure being stable. A method to find out main characteristics of the domains, such as their size and concentration, is developed for both chaotic and regular (ordered) structures

Nanoscale Co/C multilayers for "carbon window" Schwarzchild objective

The formation features of the Co/C multilayer with ≈2.3 nm period have been studied with aim to form a Schwarzschild objective on a "carbon window" for medical and biological investigations. A sequence of multilayer deposition on curved substrates has been proposed that provides the matched functioning of both objective mirrors. The interaction features of the Co and C layers during deposition, period and reflectivity changes under heating have been considered

Size effects in thin n-PbTe films

The effect of the film thickness d on the Seebeck coefficient S, the Hall coefficient RH, electrical conductivity σ, charge carrier mobility μH and thermoelectric power factor S²σ of thin films (d = 7-235 nm) prepared by thermal evaporation of n-type PbTe polycrystals doped with InTe in vacuum onto (001)KCl substrates was investigated. It was established that at d ≈ 20 nm, an inversion of the conductivity type (p → n) occurs, which is attributed to a change in the thermodynamic equilibrium conditions in films as compared with bulk crystals and\or to partial re-evaporation of In atoms. In the thickness range d 20 nm, the thickness dependences of the properties exhibit an oscillatory behavior with the period Δ d ≈ 12 nm. The observed oscillatory character of the thickness dependences of the kinetic coefficients is attributed to the manifestation of quantum size effects. The theoretical S(d) dependence calculated in the approximation of size quantization taking into account d-dependences of the Fermi energy and a number of subbands is in good agreement with the experimental one with regard to the oscillation period