Electron surface states in short-period superlattices: (GaAs)2/(AlAs)2(1 0 0)-c(4 × 4)

The electronic structure of (GaAs)₂/(AlAs)₂(1 0 0)-c(4 × 4) superlattice surfaces was studied by means of angular-resolved photoelectron spectroscopy (ARUPS) in the photon energy range 20-38 eV. Four samples with different surface termination layers were grown and As-capped by molecular beam epitaxy (MBE). ARUPS measurements were performed on decapped samples with perfect c(4 × 4) reconstructed surfaces. An intensive surface state was, for the first time, observed below the top of the valence band. This surface state was found to shift with superlattices’ different surface termination in agreement with theoretical predictions.     

8-羟基喹啉-5-磺酸为柱前螯合荧光试剂的反相离子对高效液相色谱法连续测定锡、镓和锆的方法研究

作者利用新发现的很稳定的锆-8-羟基喹啉-5-磺酸-EDTA三元荧光络合物的特殊反应及锡和镓的络合物会被EDTA分解的选择性反应,根据作者提出的金属络合物在苯基柱上的保留机理,在试验的基础上建立荧光-反相离子对高效液相色谱法连续测定锡、镓、锆的新分析方法。方法快速,准确,干扰小,适于实际样品分析。检测限分别为1.05ng,0.20ng和0.25ng,相对标准偏差在1.2％～4.4％之间。     

Dithiophosphors?ure-O,O-diethylester zur Spurenanreicherung an Aktivkohle

Zusammenfassung Der für die Extraktion im stark sauren Medium geeignete Chelatbildner Dithiophosphorsäure-O,O-diethylester kann auch für die Spurensorption an Aktivkohle eingesetzt werden. Durch das unterschiedliche Sorptionsverhalten der Elemente ist es möglich, eine Gruppe von Elementspuren (Bi, Cd, Cu, In, Pb, Tl) selektiv aus verschiedenen Matrices abzutrennen. Am Beispiel der Analyse von Reinstgallium konnte gezeigt werden, daß die Kombination von Spurenabtrennung und mikrophysikalischem Bestimmungsschritt zu Nachweisgrenzen im ng/g-Bereich führt. Als Bestimmungsverfahren für die angereicherten Spuren wurden die Injektionsmethode der Flammen-AAS und die Schlaufen-AAS eingesetzt, da mit beiden Methoden bei sequentieller Messung noch Multielementbestimmungen aus Spurenkonzentraten von weniger als 1 ml möglich sind.

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Dithiophosphoric-acid-O,O-diethylester for trace enrichment on activated carbonI. Analysis of high-purity gallium and aluminium-determination of the element traces by flame-AAS (injection method and loop-AAS)

Summary The chelate complexing agent dithiophosphoric acid-O,O-diethylester, suitable for extraction from high acidity media, can also be put to use in trace sorption on activated carbon. Due to different sorption behaviour of elements, it is possible to separate selectively from different matrices, groups of elements (such as Bi, Cd, Cu, In, Pb, Tl). By way of example concerning the analysis of high-purity gallium, it could be demonstrated that by combination of a trace separation with a micro-physical determination step, detection limits in the ng/g-region could be reached. As a determination procedure regarding pre-concentrated traces, the injection method of flame-AAS and loop-AAS were applied, because both these methods allow sequential multielement determinations from trace concentrates of less than 1 ml.

     

Hydrogen adsorption on GaAs(0 0 1)-c(4 × 4)

Exposure of the As-terminated GaAs(0 0 1)-c(4 × 4) reconstructed surface to atomic hydrogen (H) at different substrate temperatures (50-480 °C) has been studied by reflection high-energy electron diffraction (RHEED) and scanning tunnelling microscopy (STM). Hydrogen exposure at low temperatures (∼50 °C) produces a disordered (1 × 1) surface covered with AsH_x clusters. At higher temperatures (150-400 °C) exposure to hydrogen leads to the formation of mixed c(2 × 2) and c(4 × 2) surface domains with H adsorbed on surface Ga atoms that are exposed due to the H induced loss of As from the surface. At the highest temperature (480 °C) a disordered (2 × 4) reconstruction is formed due to thermal desorption of As from the surface. The results are consistent with the loss of As from the surface, either through direct thermal desorption or as a result of the desorption of volatile compounds which form after reaction with H.     

Studien zur Reaktion von [Me2AlP(SiMe3)2]2 mit basenstabilisierten Organogalliumchloriden und ‐hydriden

Investigations on the Reactivity of [Me₂AlP(SiMe₃)₂]₂ with Base‐stabilized Organogalliumhalides and ‐hydrides [Me₂AlP(SiMe₃)₂]₂ ( 1 ) reacts with dmap?Ga(Cl)Me₂, dmap?Ga(Me)Cl₂, dmap?GaCl₃ and dmap?Ga(H)Me₂ with Al‐P bond cleavage and subsequent formation of heterocyclic [Me₂GaP(SiMe₃)₂]₂ ( 2 ) as well as dmap?AlMe_xCl_3?x (x = 3 8 ; 2 3 ; 1 4 ; 0 5 ). The reaction between equimolar amounts of dmap?Al(Me₂)P(SiMe₃)₂ and dmap?Ga(t‐Bu₂)Cl yield dmap?Ga(t‐Bu₂)P(SiMe₃)₂ ( 6 ) and dmap?AlMe₂Cl ( 3 ). 2 – 8 were characterized by NMR spectroscopy, 2 and 6 also by single crystal X‐ray diffraction.     

Gallium‐Indium Ordering in the Complex [Ni2Ga3In] Network of GdNi2Ga3In

Polycrystalline samples of the isotypic quaternary compounds RENi₂Ga₃In (RE = Y, Gd – Tm) were obtained by arc‐melting of the elements. Crystals of the gadolinium compound were found by slow cooling of an arc‐melted button of the initial composition “GdNiGa₃In”. All samples were characterized by powder X‐ray diffraction. The structure of GdNi₂Ga_2.89In_1.11 was refined from single‐crystal X‐ray diffractometer data: new type, Pnma, a = 2426.38(7), b = 418.17(2), c = 927.27(3) pm, wR₂ = 0.0430, 1610 F² values and 88 variables. Two of the six crystallographically independent gallium sites show a small degree of Ga/In mixing. The nickel atoms show tricapped trigonal prismatic coordination by gadolinium, gallium, and indium. Together, the nickel, gallium, and indium atoms build up a complex three‐dimensional [Ni₂Ga₃In]^δ– network, which leaves cages for the gadolinium atoms. The indium atoms form zigzag chains with In–In distances of 337 pm. The crystal chemical similarities of the polyhedral packing in the GdNi₂Ga₃In and La₄Pd₁₀In₂₁ structures are discussed.     

镓,铟与酸性铬深蓝络合物吸附波的研究及其应用

在醋酸盐缓冲溶液中，用单扫示波极谱法分别获得了镓（Ⅲ）、铟（Ⅲ）与酸性铬深蓝灵敏的络合物吸附波。两个波的峰电位分别为－０５１Ｖ和－０６３Ｖ（ｖｓＳＣＥ），镓（Ⅲ）的线性范围为７２０×１０－７～７４６×１０－６ｍｏｌ／Ｌ；铟（Ⅲ）为１７４×１０－７～４８８×１０－６ｍｏｌ／Ｌ。作者研究了该电极反应机理。该法用于矿石中镓、铟的测定，结果满意。