Silicon nanowhiskers in the diameter range of 70 to 200 nm were grown on 〈111〉-oriented silicon substrates by molecular-beam epitaxy. Assuming the so-called “vapor–liquid–solid” (VLS) growth process to operate, we initiated the growth by using small clusters of gold at the silicon interface as seeds. The in situ generation of the Au clusters as well as the growth parameters of the whiskers are discussed. The experimentally observed radius dependence of the growth velocity of the nanowhiskers is opposite to what is known for VLS growth based on chemical vapor deposition and can be explained by an ad-atom diffusion on the surface of the whiskers.

The oxygen ion conductivity of YSZ (ZrO(2) + 9.5 mol% Y(2)O(3))/Y(2)O(3) multilayer systems is measured parallel to the interfaces as a function of temperature between 350 and 700 degrees C. The multilayer samples are prepared by pulsed laser deposition (PLD). The film thicknesses, the crystallinity, the texture and the microstructure are investigated by SEM, XRD, HRTEM and SAED. To separate the interface contribution of the total conductivity from the bulk contribution the thickness of the YSZ and Y(2)O(3) layers is varied systematically. The total conductivity of the YSZ films increases when their thickness is decreased from 0.53 microm to 24 nm. It depends linearly on the reciprocal thickness of the individual layers, thus on the number of YSZ/Y(2)O(3) interfaces. This behaviour results from the parallel connection between individual conduction paths in the bulk and the interfacial regions. The activation energy for the ionic conductivity decreases from 1.13 to 0.99 kJ mol(-1) by decreasing the thicknesses of the individual YSZ layers. HRTEM studies show that the YSZ/Y(2)O(3) interfaces are semicoherent. The correlation between interface structure and ionic conduction is discussed.

The use of bismuth-layered perovskite films for planar-type nonvolatile ferroelectric random-access memories requires films with spontaneous polarization normal to the plane of growth. Epitaxially twinned a axis-oriented La-substituted Bi4Ti3O12 (BLT) thin films whose spontaneous polarization is entirely along the film normal were grown by pulsed laser deposition on yttria-stabilized zirconia-buffered Si(100) substrates using SrRuO3 as bottom electrodes. Even though the (118) orientation competes with the (100) orientation, epitaxial films with almost pure (100) orientation were grown using very thin, strained SrRuO3 electrode layers and kinetic growth conditions, including high growth rates and high oxygen background pressures to facilitate oxygen incorporation into the growing film. Films with the a-axis orientation and having their polarization entirely along the direction normal to the film plane can achieve a remanent polarization of 32 microcoulombs per square centimeter.

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Wafer-scale fabrication of ferroelectric oxide nanoshell tubes as well as ordered nanotube arrays have been accomplished using a simple and convenient fabrication method that allows full tailoring of tube dimensions as well as array pattern and size. Using different silicon and alumina templates, barium titanate and lead zirconate titanate tubes with diameters ranging from 50 nm up to several micrometers meter and lengths of more 100 m have been fabricated. Ferroelectric switching of submicrometer tubes has been shown using piezoresponse scanning probe microscopy.