Untersuchungen zur atomspektroskopischen Spurenanalyse in AIII BV-Halbleitermikroproben—VI Untersuchungen zur Schichtabtrennung,Profil- und Spurenanalyse an InSb-Materialien

A method for the determination of distribution profiles and traces in InSb-materials is described. Stripping of the layers of several nm thickness was achieved by anodic oxidation (galvanostatic conditions). The stripping method was optimized, and the thickness of the layers stripped was determined by ellipsometric measurements. Traces of elements were determined by atomic emission and flameless atomic-absorption spectrometry. Detection limits in the range of 10¹⁷ atoms/cm³ for a 1-cm² surface layer 60 nm thick were observed. Distribution profiles for Mg and Te in InSb are shown.     

Untersuchungen zur atomspektroskopischen spurenanalyse in AIIIBV-halbleiter-mikroproben—III: Untersuchungen zur schichtabtrennung und zur spurenanalyse in dünnen GaAs schichten

Three methods for stripping thin layers of GaAs have been compared with regard to depth of layer and reproducibility. They are (1) chemical etching with methanolic bromine solution, (2) mechanical separation with a microtome, (3) chemical etching after a preliminary amperostatic anodic oxidation. Conditions were optimized. The depth of strip was 0.4 μm for chemical etching, 1 μm for the mechanical separation and 0.02 μm for the anodic oxidation method. Thus the anodic oxidation is specially suitable for profile analysis, and the mechanical method for investigation of thicker layers; chemical etching lies between them. The trace elements in the micro samples thus obtained were determined by d.c. are atomic-emission spectrography (AES) and atomic-absorption spectrometry with electrothermal atomization in a graphite tube (AAS). The absolute and relative detection limits of AAS for the 0.1–0.2 mg micro samples were on average better by an order of magnitude than those of AES. The advantage of AES lies in the possibility of simultaneous determination of several elements. in der Möglichkeit der Simultanbestimmung mehrerer Elemente.     

Electromagnetic scattering by a homogeneous chiral obstacle in a chiral environment

Time-harmonic electromagnetic waves are scattered by a homogeneouschiral obstacle embedded in a chiral environment. The correspondingtransmission problem is reduced, via Bohren's decomposition,to an integral equation over the interface between the obstacleand the surrounding medium. This integral equation is shownto be uniquely solvable except for a discrete set of electromagneticparameters of the obstacle.