Determination of the inelastic mean free path of electrons in GaAs and InP after surface cleaning by ion bombardment using elastic peak electron spectroscopy

The inelastic mean free path (IMFP) of electrons is an important material parameter needed for quantitative AES, EELS and non-destructive depth profiling. The distinction between the terms for IMFP and the attenuation length (AL) has been established by ASTM standards. A practical experimental method for determining values of the IMFP is elastic peak electron spectroscopy (EPES). In this method, experimentally determined ratios of elastically backscattered electrons from test surfaces and from a Ni reference standard are compared with the values evaluated theoretically.The present paper reports systematic measurements of the IMFP by EPES for GaAs and InP. They are carried out in two laboratories using two different electron spectrometers: a CMA in Budapest and DCMA in Warsaw. Prior to measurements, the samples were amorphized by high-energy Ar⁺ ions (100–400 keV), and the surface composition was determined by quantitative XPS. Argon cleaning produces enrichment of samples in the surface layer in Ga (80%) and In (70%), respectively. The experiments refer to a such modified sample surface that was considered in Monte Carlo calculations. The experimental data were analyzed using calibration curves from Monte Carlo calculations which account for multiple elastic scattering events. This approach has been used previously for elemental solids and is now extended to amorphized binary compounds. The experimental values of IMFP obtained in both laboratories exhibited a reasonable agreement with the available literature data in the 0.1–3.0 keV energy range. With respect to the information depth of EPES, the experimental results refer to the bulk composition within a reasonable extent.     

光热材料在太阳能海水脱盐中应用的研究进展

用于海水脱盐的太阳能界面蒸发装置因其绿色环保、简单高效以及适用范围广等优点,受到了广泛关注。与传统的体积式蒸发装置不同,太阳能界面蒸发装置将太阳光的收集和蒸汽的产生锁定在空气-水的界面,无需从底部加热整体水来产生蒸汽,极大提高了能源利用效率。本文详细介绍了太阳能界面水蒸发装置的重要组成部分——光热材料的光热转换机理、材料种类以及材料的性能;探讨了高效海水净化太阳能蒸发装置的设计策略(增强光吸收、充足水供应、耐盐排盐等)。在此基础上,总结了基于界面蒸发中的太阳能蒸发装置的研究进展,展望了新型太阳能蒸发装置在海水净化领域的发展前景。     

三个耦合的非扩散Lorenz系统的全局混沌同步

以Lyapunov稳定性理论和矩阵论为基础,针对非扩散Lorenz系统,提出了一种三个耦合的恒等系统的全局混沌同步方案.该方案的关键是耦合参数的选取.通过选择适当的耦合参数,使得三个系统的状态变量达到同步,并利用Mathematic软件进行数值仿真.理论分析和仿真结果都表明了该方法的有效性.     

A new far-infrared broadband absorption in non-rigid polar molecules

A new far-infrared broadband absorption has been observed for non-rigid ketone molecules in the frequency range 220 to 340 cm⁻¹. It has been found that the amplitude of this absorption increases with an increase in the flexibility of the molecule. Such an increase in the amplitude of this absorption is accompanied by a corresponding reduction in that of the Poley absorption.     

Alkylatlon orientation rules in conjugate addition of grignard reagents to nitropyrrole and nitrothiophene systems

Conjugate addition of various Grignard reagents to 1-alkyl-2-nitropyrroles and to 2-nitrothiophene has been investigated. 1-Alkyl-2-nitropyrroles undergo alkylation at 3 and 5 positions with prevalence of the latter isomer. On the contrary, in 2-nitrothiophene system, formation of the 3-isomer prevails. In both systems, a bulkier Grignard reagent favours the 5-isomer formation. This trend can be reversed increasing steric hindrance exerted by the 1-substituent of 2-nitropyrrole. 1-(Tri-isopropylsilyl)-3-nitropyrrole and 3-nitrothiophene give exclusively the 2-isomer. This rection allows 2-alkyl-3-nitrothiophenes and pyrroles to be synthesized with a one-pot procedure instead of the classical multi-stage reaction.     

Synthesis,characterization, and magnetic properties of mixed-valence europium-ammonia intercalation compounds of titanium disulfide

Europium-ammonia intercalation compounds of titanium disulfide have been synthesized by reaction of EuNH₃ solutions with TiS₂, characterized by thermogravimetric analysis and powder X-ray diffraction, and investigated by electron paramagnetic resonance, magnetization, and magnetic susceptibility measurements. These materials crystallize in a 3R-type structure in which every layer is occupied by intercalated species. The intercalation of NH₃ is accompanied by the formation of NH⁺₄ until a critical electron concentration of 0.22 mole el/mole TiS₂ have been transferred to the TiS₂ conduction band. Although Eu³⁺ is the predominant Eu species for x > 0.001, Eu²⁺ is also formed, possibly from the reduction of Eu³⁺ in the van der Waals gap. These mixed-valence compounds are best described by the formulas (Eu³⁺)_x′(Eu²⁺)_x″(NH⁺₄)_y′(NH₃)_y″TiS^{(3x′+2y″+y′)−}₂ for 3x′ + 2x″ + y′ < 0.22 and (Eu³⁺)_x′(Eu²⁺)_x″(NH₃)_y″TiS^{(3x′+2x″)−}_n2 for 3x′ + 2x″ ≥ 0.22.     

The conditional distributivity condition for T-uninorms revisited

This paper studies the conditional distributivity for T-uninorms over uninorms in the most general setting, transforming it into the (conditional) distributivity equation involving two uninorms.

     

Dynamics of entanglement in one-dimensional Ising chains with two- and three-body interactions

The evolution of entanglement in a one-dimensional Ising chain with both two-body and three-body interactions, under two types of initial states, is numerically simulated. We analyse three problems concerning the dynamics of pairwise entanglement: (i) the possibility of generating large entanglement from an initial separable state by the use of a selective irradiation scheme; (ii) the effect of three-body interaction on the generation of entanglement from an initial separable state; (iii) the effect of three-body interaction on the decay of the entanglement from a state with only (m,n)-pair maximal entangled, and the rest in product form. It is shown that a large pairwise concurrence C_mn can be obtained when the resonant, transverse radio-frequency fields are selectively switched on from the mth to nth spins. Three-body interaction will decrease the oscillation amplitude of the nearest neighbour concurrence, while the oscillation amplitude of remote pairwise concurrence will be greatly increased with the consideration of three-body interactions. For an initial (m,n)-pair maximal entangled state, a slow decay of the pairwise concurrence C_mn is found with the introduction of three-body interactions.