A model of nanosecond laser ablation of compound semiconductors accounting for non-congruent vaporization

We report a model of nanosecond laser ablation of compound semiconductors taking into account stoichiometry loss as a result of different volatilities of the material components. The model is based on the heat-flow equation for the bulk material and the diffusion equation for its atomic constituents and takes into account variations of material properties as functions of temperature and composition. Changing the optical response which results from stoichiometry violation is described within the concept of an effective medium and a multi-layer reflection model is applied. For cadmium telluride, as an example, the processes of ablation, melting, and resolidification under the action of a KrF laser have been studied in dynamics for particular experimental conditions in a wide range of laser fluences from the ablation threshold to the plasma shielding regimes described by the effective plasma plume representation. Multi-shot irradiation regimes have been investigated and the mechanism of the irradiation-controlled stoichiometry reversal has been elucidated.     

Ultrafast magnon generation in an Fe film on Cu(100)

We report on a combined experimental and theoretical study of the spin-dependent relaxation processes in the electron system of an iron film on Cu(100). Spin-, time-, energy- and angle-resolved two-photon photoemission shows a strong characteristic dependence of the lifetime of photoexcited electrons on their spin and energy. Ab?initio calculations as well as a many-body treatment corroborate that the observed properties are determined by relaxation processes involving magnon emission. Thereby we demonstrate that magnon emission by hot electrons occurs on the femtosecond time scale and thus provides a significant source of ultrafast spin-flip processes. Furthermore, engineering of the magnon spectrum paves the way for tuning the dynamic properties of magnetic materials.     

Definability of closure operations in the <Emphasis Type="Italic">h</Emphasis>-quasiorder of labeled forests

We prove that natural closure operations on quotient structures of the h-quasiorder of finite and (at most) countable k-labeled forests (k ≥ 3) are definable provided that minimal nonsmallest elements are allowed as parameters. This strengthens our previous result which holds that each element of the h-quasiorder of finite k-labeled forests is definable in the first-order language, and each element of the h-quasiorder of (at most) countable k-labeled forests is definable in the language L _ω1ω; in both cases k ≥ 3 and minimal nonsmallest elements are allowed as parameters. Similar results hold true for two other relevant structures: the h-quasiorder of finite (resp. countable) k-labeled trees and k-labeled trees with a fixed label on the root element.     

Xenon nano-beams for materials research

The advantage of focused Xe⁺ beams over other rare gas species have been investigated [Zhukov, V.; Kalbitzer, S. Russ. Microelectron. 2011, 40 (1), 17–24]. In particular, the higher operation temperature of a super-tip gas field ion source for xenon ions is one outstanding technical feature. The properties of focused Xe⁺ beams are estimated with special reference to optimised ion-optical transport systems. Applications to both ion beam materials modification and ion beam materials analysis are outlined.     

Electronic band structure and optical absorption of nanotubular zinc oxide doped with Iron, Cobalt, or Copper

The absorption spectra of the precursor-derived solid solutions Zn_{1 ? x} M _x O (M = Fe, Co, Cu) with a tubular morphology of aggregates have been investigated in the ultraviolet and visible regions. The maximum metal concentration x in the Zn_{1 ? x} M _x O solid solutions is 0.075 for iron, 0.2 for cobalt, and 0.1 for copper. It has been found that the optical absorption and the band gap of the Zn_{1 ? x} M _x O compounds depend on the type of dopant. The obtained experimental data have been interpreted using the results of the performed ab initio calculations of the electronic band structure and optical absorption.     

Absorption and emission of terahertz radiation in doped GaAs/AlGaAs quantum wells

Spontaneous emission of terahertz radiation from structures with GaAs/AlGaAs quantum wells in a longitudinal magnetic field has been studied. It is shown that some bands in the emission spectrum can be related to radiative electron transitions between resonant and localized impurity states, as well as to the transitions with participation of subband states. The temperature dependence of the equilibrium intraband absorption of terahertz radiation and its modulation in a longitudinal electric field in GaAs/AlGaAs quantum wells has been investigated.     

Nitrogen-Doped Titanium Dioxide Thin Films Formation on the Surface of PLLA Electrospun Microfibers Scaffold by Reactive Magnetron Sputtering Method

Plasma Chemistry and Plasma Processing - Nitrogen-doped thin titanium dioxide films formed by the reactive magnetron sputtering method on the surface of PLLA electrospun microfibers scaffold were...     

Single domain wall dynamics in thin magnetic wires

Here we present the low-field domain wall dynamics in thin magnetic wires. It is shown that the domain wall dynamics at low applied fields is described by the power law. The role of all parameters in the domain wall dynamics was studied in a wide temperature range. The power exponent β, which should reflect the changes of the domain wall shape due to its pinning on the local defects, is almost temperature independent. This points to the fact the mechanism of the domain wall pinning does not change with the temperature in the temperature range 77–350 K. This fact is also consistent with the temperature dependence of the switching field H_sw.     

Influence of Alumina Nanoparticles on the Structure and Physical and Mechanical Properties of Pure Aluminum

Russian Physics Journal -