Abstract: We studied the morphology of ramps in REBa2CU3O7 (REBCO) epitaxial films on SrTiO3 substrates, fabricated by RF magnetron sputter deposition and pulsed laser deposition (PLD), by scanning probe microscopy (SPM) and high resolution electron microscopy (HREM). The ramps were fabricated by Ar ion beam etching using masks of standard photoresist and TIN. AFM-studies on ramps in sputter deposited films show a strong dependence, i.e. formation of facets and ridges, on the angle of incidence of the ion beam with respect to the substrate surface as well as the rotation angle with respect to the crystal axes of the substrate. Ramps in pulsed laser deposited films did not show this dependence, Furthermore, we studied the effect of an anneal step prior to the deposition of barrier layers (i.e. PrBa2CU3O7, SrTiO3, CeO2) on the ramp. First results show a recrystallization of the ramp surface, resulting in terraces and a non-homogeneous growth of the barrier material on top of it. The thickness variations, for thin layers of barrier material, con even become much larger than expected from the amount of deposited material and are dependent on the deposition and anneal conditions. HREM studies show a well defined interface between barrier layer and electrodes. The angle of the ramp depends on the etch rate of the mask and REBCO, and on the angle of incidence of the ion beam. TiN has a much lower etch rate compared to photoresist, resulting in an angle of the ramp comparable to the angle of incidence, resulting in a low etching rate on the ramp. These results will lead to improved electrical characteristics of ramp-type junctions.

Abstract: La1-xCaxMnO3-delta (LCMO) thin films are grown by pulsed laser deposition on a (100) SrTiO3 substrate at temperatures between 530 degrees C and 890 degrees C. The magnetotransport properties show a high negative magnetoresistance and a shift of the maximum of the R(T) curve as function of temperature. The Curie temperature changes with deposition temperature and film quality in the range of 100-220K. The film quality is characterised by X-ray diffraction and transmission electron microscopy (TEM); film and target compositions were verified by atomic emission spectroscopy. The local structure of the film depends on the growth conditions and substrate temperature. TEM reveals a slight distortion of the film leading to a breakdown of the symmetry from orthorhombic to monoclinic. At the highest growth temperatures, a well defined interface is observed within the LCMO film, parallel to the substrate surface; this interface divides the film into two lamellae with a different microstructure. The lamella close to the substrate is perfectly coherent with the substrate, suggesting that it is strained as a result of the lattice parameter mismatch; the upper lamella shows a typical domain structure with unusual translation interfaces characterised by a displacement vector of the type 1/2[010](m) and 1/2[001](m) when referred ten the monoclinic lattice.

Abstract: A method to correlate microstructure from cross-section transmission electron microscopy (TEM) investigations and transport properties of a single well characterized high-T-c artificial grain boundary junction is reported. A YBa2Cu3O7-delta 45 degrees twist junction exhibiting the typical phenomenology of high T-c Josephson weak links was employed. The TEM sample preparation is based on focused ion beam etching and allows to easily localize the electron transparent area on a microbridge. The reported technique opens clear perspectives in the determination of the microstructural origin of variations in Josephson junction properties, such as the spread in I-c and IcRN values and the presence of different transport regimes in nominally identical junctions. (C) 1999 American Institute of Physics. [S0003-6951(99)03404-X].