Propagation length of surface plasmon polaritons excited by a 1D plasmonic grating

The propagation length of surface plasmon polaritons (SPPs) is investigated experimentally using a 1D metallic grating fabricated on a higher refractive index substrate (Gallium Phosphide, GaP). The experimentally measured value propagation length of the SPP (L_SPP) at 785 nm wavelength is 13.33 ± 0.13 μm, which is close to the theoretical value of the L_SPP on an ideal Au-thin film. The SPP resonance observed in far-field measurements confirms the underlying process and the related effects on the L_SPP measured by scanning near field optical microscope (SNOM). Far-field measurements shows that L_SPP is associated with the full width at half maximum (FWHM) of the SPP resonance which in-turn associated with in-plane directional scattering of the SPP.     

Hierarchically structured copper gallium spinels through microwave hydrothermal methods

The promising structural features of the defect spinel-type oxide γ-Ga₂O₃ and its application potential as a host for new nanoscale solid solutions have been far less explored than its analog γ-alumina, which is widely used in catalysis. Therefore, new synthetic approaches are required to access transition metal-doped γ-Ga₂O₃ materials on the nanoscale. We have established the first microwave–hydrothermal route for the challenging incorporation of Cu²⁺ ions into a nanostructured γ-Ga₂O₃ matrix. Homogeneous γ-Ga₂O₃:Cu²⁺ materials with high surface areas are formed within less than 30 min, and the copper content can be adjusted through the synthetic parameters. The copper distribution within the spinel matrix was analyzed with a wide range of compositional, structural, spectroscopic and magnetic characterizations.     

Effect of arsenic species on the kinetics of GaAs nanowires growth by molecular beam epitaxy

GaAs nanowires (NWs) are grown on GaAs (1 1 1) B substrates in a molecular beam epitaxy system, by Au-assisted vapor–liquid–solid growth. We compare the characteristics of NWs elaborated with As₂ or As₄ molecules. In a wide range of growth temperatures, As₄ leads to growth rates twice faster than As₂. The shape of the NWs also depends on the arsenic species: with As₄, regular rods can be obtained, while pencil-like shape results from growth with As₂. From the analysis of the incoming fluxes, which contributes to the NWs formation, we conclude that the diffusion length of Ga adatoms along the NW sidewalls is smaller under As₂ flux as compared to that under As₄ flux. It follows that As₂ flux is favourable to the formation of radial heterostructures, whereas As₄ flux is preferable to maintain pure axial growth.     

DX-Like behavior of Se-impurity centers in gasb under hydrostatic pressure

Abstract

Hall coefficient (R_H) and electrical resistivity measurements have been performed as a function of temperature (between 77 K and 300 K) and under hydrostatic pressures (up to 15 kbar) on a set of Se-doped GaSb samples with impurity concentrations in the range 8×10¹⁷ cm^?3 - 1×10¹⁸ cm^?3. With increasing pressure at 300 K, the electrons are strongly trapped into a resonant impurity level. The pressure induced occupation of this level leads to time-dependent effects at T<120 K. The activated thermal electron emission over a potential barrier E<sb>B = 300×30 meV gives clear evidence for a large lattice relaxation around the impurity centers characteristic for DX-like behavior.     

Multiple-step annealing for 50% enhanced p-conductivity of GaN

In this article, multiple-step rapid thermal annealing (RTA) processes for the activation of Mg doped GaN are compared with conventional single-step RTA processes. The investigated multiple-step processes consist of a low temperature annealing step at temperatures between 350°C and 700°C with dwell times up to 5 min and a short time high temperature step. With optimized process parameters, and multiple-step processes, we achieved p-type free carrier concentrations up to 1–2×10¹⁸ cm⁻³. The best achieved conductivity, so far, lies at 1.2 Ω⁻¹ cm⁻¹. This is a 50% improvement compared to conventional single-step process at 800°C, 10 min.     

Structure of nanocrystalline ammonothermal GaN in dependence of temperature and type of acidic mineralizer

This study investigated ammonothermal synthesis of nanocrystalline gallium nitride (GaN) in supercritical ammonia with acidic mineralizers NH₄X (X=Cl, Br, I) at 400–500 °C. Results showed that three types of acidic mineralizers could effectively accelerate the formation of GaN. The mixed hexagonal/cubic phase fractions and lattice parameters of nanocrystalline GaN were calculated by the Rietveld refinement method. SEM showed an agglomerate of nanocrystalline GaN. A considerable amount of GaN was synthesized using NH₄Cl as the mineralizer, however, there was no yield using NH₄Br or NH₄I at 400 °C. For acidic mineralizers, both hexagonal structures (wurtzite) and cubic structures (zincblende) were obtained in ammonothermal synthesis by XRD and Raman measurement. GaN synthesized with NH₄Br and NH₄I showed mixed phases of hexagonal-GaN (h-GaN) and cubic-GaN (c-GaN) at 450–500 °C. In the case of NH₄Cl mineralizer, GaN only exhibited mixed phases of h-GaN and c-GaN at 500 °C, but pure h-GaN at 400–450 °C. Based on the results, NH₄Cl favored pure h-GaN, and NH₄Br and NH₄I favored c-GaN at 400–450 °C.     

Mononuclear gallium(III) complexes based on salicylaldoximes: Synthesis,structure and spectroscopic characterization

The reactions of Ga(acac)₃ with salicylaldoxime (saoH₂) and methyl-salicylaldoxime (Me-saoH₂) in dichloromethane/hexane afforded the complexes [Ga(acac)(saoH)₂] (1) and [Ga(acac)₃][Ga(acac)(MesaoH)₂] (2), respectively, in high yields. The crystal structures of 1 and 2 have been determined by single-crystal X-ray crystallography. Both complexes are mononuclear with the Ga(III) atoms being in octahedral environments surrounded by two bidentate chelate R-saoH⁻ and one bidentate chelate acac⁻ ligands. A [Ga(acac)₃] moiety has co-crystallized along with the methylsalicylaldoximato complex. Characteristic IR as well as NMR data are discussed in terms of the nature of bonding in the structures of the two complexes. ¹H and ¹³C NMR data in CDCl₃ indicate that the salicylaldoximato complexes isomerize in solution.     

新Schiff碱SAAQ的合成及其分析应用研究(Ⅰ)——荧光光度法测定镓

常用于测定镓的荧光试剂有8-羟基喹啉类、Schiff碱类、偶氮类及黄酮类等^[1～8]。而水杨醛缩-8-氨基喹啉(简称SAAQ)的合成及分析应用研究尚未见报道.本文研究了该试剂的合成方法及其分析应用.     

A novel cesium hydroxygallophosphate with a layered structure built up of rutile ribbons: CsGa2(OH)2[(PO4)H(PO4)]

A new cesium gallophosphate, CsGa₂(OH)₂[(PO₄)H(PO₄)], with an original layer structure has been synthesized by hydrothermal route and characterized by single-crystal X-ray diffraction (R=0.0344, R_w=0.0319). Its structure crystallizes in the monoclinic space group P2₁/a with cell parameters , , , β=93.36(4)° and Z=2. It consists of [Ga(OH)PO₄]_∞ layers built up of rutile ribbons interconnected through PO₄ tetrahedra. The structure of CsGa₂(OH)₂[(PO₄)H(PO₄)] is closely related to those of (NH₄)Ga(OH)PO₄ and (en)Ga₂(OH)₂(PO₄)₂ (en=ethylenediamine [H₃N(CH₂)₂NH₃]²⁺). The three structures differ mainly from each other by the relative positions and the spacing of the successive layers, which are governed by different hydrogen bonding modes between [Ga(OH)PO₄]_∞ layers and the interleaved species. The title compound presents strong symmetric hydrogen bonds O---H---O which bridge two PO₄ tetrahedra of two successive layers. As a consequence, the distance between the layers is significantly shorter than in the two other amine compounds.     

Radiation effects in ionic solids

Current development of the research of radiation damage in ionic solids is reviewed. Emphasis is placed on the correlation between elementary radiation damage processes and the atomic and electronic structures of the materials. Both the radiation damage induced by electronic excitation and by elastic collision are treated. For the former two crucial processes, the self-trapping of excitons and the formation of stable Frenkel pairs from the self-trapped excitons in several materials, is discussed in terms of the structures of materials. Deficiency in the available data on the knock-on threshold energies are pointed out. Available information of Frenkel pairs produced by electronic and elastic encounters is surveyed. Possible models of defect clustering are summarized and existing information on clustering is discussed on their basis.