Ruddlesden-Popper faults in LaNiO3/LaAlO3 superlattices

Scanning transmission electron microscopy in combination with electron energy-loss spectroscopy is used to study LaNiO3/LaAlO3 superlattices grown on (La,Sr)AlO4 with varying single-layer thicknesses which are known to control their electronic properties. The microstructure of the films is investigated on the atomic level and the role of observed defects is discussed in the context of the different properties. Two types of Ruddlesden-Popper faults are found which are either two or three dimensional. The common planar Ruddlesden-Popper fault is induced by steps on the substrate surface. In contrast, the three-dimensionally arranged Ruddlesden-Popper fault, whose size is in the nanometer range, is caused by the formation of local stacking faults during film growth. Furthermore, the interfaces of the superlattices are found to show different sharpness, but the microstructure does not depend substantially on the single-layer thickness.Comment: 14 pages, 6 figure

Observations of fronts in the North Sea

The persistent presence of a cold bottom layer and associated bottom fronts was observed in the stratified central North Sea during an observational program in 1981 and 1982. Moored instruments, capturing a snap-shot of such a front while it was advected past these moorings, revealed the simultaneous presence of a well-defined frontal jet with velocities up to 15 cm s−1. The Coriolis force acting on this jet appeared to be in geostrophic balance with the locally intense pressure gradient forces. Hydrographic surveys revealed the presence of both small-scale and large-scale baroclinic waves on this front, the latter reaching wavelengths of 5–10 internal Ross by radii. Some evidence for a weak secondary circulation in the cross-frontal plane was obtained from the observed deformation of isolines near the front