Protected Long-Distance Guiding of Hypersound Underneath a Nanocorrugated Surface

In nanoscale communications, high-frequency surface acoustic waves are becoming effective data carriers and encoders. On-chip communications require acoustic wave propagation along nanocorrugated surfaces which strongly scatter traditional Rayleigh waves. Here, we propose the delivery of information using subsurface acoustic waves with hypersound frequencies of ∼20 GHz, which is a nanoscale analogue of subsurface sound waves in the ocean. A bunch of subsurface hypersound modes are generated by pulsed optical excitation in a multilayer semiconductor structure with a metallic nanograting on top. The guided hypersound modes propagate coherently beneath the nanograting, retaining the surface imprinted information, at a distance of more than 50 μm which essentially exceeds the propagation length of Rayleigh waves. The concept is suitable for interfacing single photon emitters, such as buried quantum dots, carrying coherent spin excitations in magnonic devices and encoding the signals for optical communications at the nanoscale

Molten Chlorides as the Precursors to Modify the Ionic Composition and Properties of LiNbO3 Single Crystal and Fine Powders

Modifying lithium niobate cation composition improves not only the functional properties of the acousto- and optoelectronic materials as well as ferroelectrics but elevates the protonic transfer in LiNbO3-based electrolytes of the solid oxide electrochemical devices. Molten chlorides and other thermally stable salts are not considered practically as the precursors to synthesize and modify oxide compounds. This article presents and discusses the results of an experimental study of the full or partial heterovalent substitution of lithium ion in nanosized LiNbO3 powders and in the surface layer of LiNbO3 single crystal using molten salt mixtures containing calcium, lead, and rare-earth metals (REM) chlorides as the precursors. The special features of heterovalent ion exchange in chloride melts are revealed such as hetero-epitaxial cation exchange at the interface PbCl2-containing melt/lithium niobate single crystal; the formation of Li(1−x) Ca(x/2)V(x/2)Li+ NbO3 solid solutions with cation vacancies as an intermediate product of the reaction of heterovalent substitution of lithium ion by calcium in LiNbO3 powders; the formation of lanthanide orthoniobates with a tetragonal crystal structure such as scheelite as the result of lithium niobate interaction with trichlorides of rare-earth elements. It is shown that the fundamental properties of ion-modifiers (ion radius, nominal charge), temperature, and duration of isothermal treatment determine the products’ chemical composition and the rate of heterovalent substitution of Li+-ion in lithium niobate

Application of universal computer modeling system for development of LCSs with high contrast and wide viewing angles

The effective applications of universal modeling systems MOUSE-LCD for the development of new LCDs with high contrast and wide viewing angles are presented. The software enables to combine LCDs both with uni and biaxial phase retardation plates as well as to use double cell configuration for the purpose of optimization. Any type of the director distribution inside LC cell with arbitrary (nonsymmetric) tilts and twist angles can be taken into account. The wideness of viewing angles can be estimated using equi-contrast ratio and equi-transmission curves for various angles of light incidence. Special examples demonstrate the effectiveness of application of MOUSE-LCD for the purpose of the design of new color displays with high brightness and wide viewing angles

Application of special lubricating compositions to increase the efficiency of friction surface run-in

The paper presents the results of laboratory studies of a number of additives introduced during operation to motor oil of internal combustion engines. It also evaluates their impact on tribological characteristics of friction pairs. It was found that all studied additives have a positive effect on the running-in quality. Reduced wear of friction pairs, reduced surface roughness compared to base motor oil is determined. The best indicators were recorded with the FENOM additive. The decrease in wear was 46% and roughness – 23.5% compared to the base oil

Non-equilibrium electron transport induced by terahertz radiation in the topological and trivial phases of Hg1−xCdxTe

Terahertz photoconductivity in heterostructures based on n-type Hg1−xCdxTe epitaxial films both in the topological phase (x 0.16, normal band structure) has been studied. We show that both the positive photoresponse in films with x 0.16 have no low-energy threshold. The observed non-threshold positive photoconductivity is discussed in terms of a qualitative model that takes into account a 3D potential well and 2D topological Dirac states coexisting in a smooth topological heterojunction

Cap Layer Effect on Key Features of Persistent Photoconductivity Spectra in HgTe/CdHgTe Double Quantum Well Heterostructures

Persistent photoconductivity (PPC) spectra of HgTe/CdHgTe heterostructures with double quantum wells with different cap layers have been studied in the radiation excitation range 0.62–3.1 eV. We have shown that the material of the cap layer defines key features of the PPC spectra—local extrema—and their origin. An unusual oscillatory behavior of the PPC spectra is demonstrated. Such a behavior is shown to be independent of both cap and barrier layers