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Reflectance measurements under normal incidence of light and variable angle spectroscopic ellipsometry (SE) studies are applied for characterizing hexagonal GaN films grown by molecular beam epitaxy on both GaAs (111)B and 6H-SiC substrates. A comparison of the reflectance above the band gap with model calculations for a smooth film yields definitely the root mean square surface roughness. By analyzing the envelopes of the reflectance spectra, the influence of a buffer layer and/or a non-abrupt substrate/film interface is verified and qualitative conclusions about the interface properties are deduced which are emphasized by transmission electron microscopy studies. On this basis a suitable model for data fitting is established which contains only a small number of parameters to be adjusted. From the fit, the complex refractive index versus photon energy as well as the thicknesses of the active layer and the interlayers are obtained. A meticulous analysis of the SE data below the band gap shows that from those studies the extraordinary refractive index of hexagonal GaN can be determined for the first time.

The structure evolution characteristics of NdF 3 thin films has been analysed concerning texture and grain morphology. The structure could be classified according to the structure zone models, and the growth mode could be related to zone T and zone II. Contamination of the films by residual gases was found to inhibit the migration of grain boundaries and therefore, zone II does not appear even at high substrate temperatures in contaminated films. Stratification by MgF 2 interlayers may also result in a decrease of grain size and a smaller surface roughness. The correlation between deposition conditions, stratification, growth mode and optical properties is discussed.

Sputtered and evaporated optical Ge films are investigated using electron microscopy and diffraction, total integrated scattering, infrared reflection absorption spectroscopy, Auger electron spectroscopy, and optical transmission measurements to observe differences of the chemical composition, atomic structure, morphology, optical constants, and degradation in relation to the parameters of technology during preparation. Gesputterte und gedampfte optische Ge-Schichten werden mit Elektronenmikroskopie und -beugung, der Methode des total integrierten Streulichts, Infrarot-Reflexions-Absorptionsspektroskopie, Auger-Elektronen-Spektroskopie und durch optische Transmissionsmessungen untersucht, um Unterschiede in der chemischen Zusammensetzung, Atomstruktur, Morphologie, den optischen Konstanten und dem Degradationsverhalten der Schichten in Abhangigkeit von der Herstellungstechnologie festzustellen.

BaF2, PbF2, and CaF2 films are investigated by IRAS (infrared reflection absorption spectroscopy), ATR (attenuated total reflection), IR transmission measurements, and IR ellipsometry. Interesting features of their spectra particularly occur near 300, 1500, and 3000 cm−1. These absorptions are due to intrinsic modes, hydroxyl, and methylen, respectively. The frequencies of the vibrational modes are related to the film material, but also to its history. The so called longitudinal optical frequencies roughly coincide with corresponding values for the cubic modifications of the fluorides, where the F ions are tetrahedrically surrounded by four nearest neighbour metal ions. Polarization dependent measurements hint at an anisotropic incorporation of water molecules in some cases. According to the lower melting point of PbF2 its water content can be reduced by heating above 373 K more quickly than it is possible for BaF2 films. This is proved by ATR measurements. BaF2-, PbF2- und CaF2-Schichten werden mittels IRAS (Infrarotreflexionsabsorptionsspektroskopie), ATR (gedampfte Totalreflexion), IR-Transmissionsmessungen und IR-Ellipsometrie untersucht. Interessante Einzelheiten ihrer Spektren treten insbesondere in der Nahe von 300, 1500 und 3000 cm−1 auf. Diese Absorptionen werden durch Eigenmoden, Hydroxyl bzw. Metylen verursacht. Die Frequenzen der Schwingungsmoden werden mit dem Schichtmaterial sowie mit dessen Vorbehandlung verknupft. Die sogenannten longitudinalen optischen Frequenzen koinzidieren naherungsweise mit entsprechenden Werten fur die kubischen Modifikationen der Fluoride, wo die F-Ionen tetraedrisch von vier nachsten Nachbarmetallionen umgeben sind. Polarisationsabhangige Messungen deuten auf einen anisotropen Einbau von Wassermolekulen in einigen Fallen hin. Entsprechend dem niedrigeren Schmelzpunkt von PbF2 kann sein Wassergehalt durch Aufheizen oberhalb 373 K schneller reduziert werden, als es fur BaF2-Schichten moglich ist. Dies wird durch ATR-Messungen bestatigt.

The energy and current sensitivity of a flat thin film SQUID is increased by two types of transformers. The transformers are galvanically coupled to the SQUID and may be used down to zero frequency. A detailed design is given for the SQUID and the superconducting transformers. A practical transformer combination is described which has a current gain of 5.7 × 103 and an input inductance of 240 mH. The measured input current period of this transformer with the SQUID is 3.5 nA. Die Energie- und Stromempfindlichkeit eines ebenen Dunnschicht-SQUIDs wird mit zwei Arten von Transformatoren erhoht. Die Transformatoren sind galvanisch mit dem SQUID gekoppelt und konnen herunter bis zur Frequenz Null verwendet werden. Der Aufbau des SQUIDs und der supraleitenden Transformatoren wird ausfuhrlich erlautert. Eine praktische Kombination von Transformatoren mit einer Stromverstarkung von 5,7 × 103 und einer Eingangsinduktivitat von 240 mH wird beschrieben. Die experimentell bestimmte Eingangsstromperiode dieses Transformators mit dem SQUID betragt 3,5 nA.

Es wird uber experimentelle Untersuchungen an einem supraleitenden Quanteninterferometer (SQUID) berichtet, das aus dunnen, supraleitenden Schichten besteht. Als Josephson-Verbindungen werden Dayem-Brucken verwendet. Die Perioden bezuglich des Steuerstromes liegen zwischen 100 μA und 1 mA. Die Stromempfindlichkeit betragt 1 μA und die Spannungsempfindlichkeit eines mit solchen SQUID aufgebauten hochempfindlichen Galvanometers 10−14 V bei einer Zeitkonstante von 1 s. Es werden Formeln zur Berechnung der Periode und der Empfindlichkeit in Abhangigkeit von der Geometrie angegeben. A report is given on experimental studies of superconducting quantum interference devices (SQUID) consisting of thin superconducting layers. As Josephson junctions Dayem-bridges are used. The width of the current cycles caused by the control current was found to have values between 10−4 and 10−3 A. With a current sensitivity of 10−6 A and a time constant of 1 s the voltage sensitivity of a high-sensitivity galvanometer constructed with such a SQUID is 10−14 V. Formulae are given for calculating the current cycles and the sensitivity in dependence on the geometry.