The dielectric properties of (100)-oriented epitaxial SrTiOs films as used in high-T, heterostructures have been studied as a function of temperature and applied electric field by using in situ grown heterostructures (Mg/SrTiOs/SrTiOs. Nb and Au/YBasCusOq /SrTiOs/SrTiOs. Nb). The dielectric behavior of these films is characterized by a rather low sample capacitance as compared to bulk single-crystal values and by occurrences of maxima in the capacitance-voltage and capacitancetemperature curves. The maximum attainable polarization was found to be 80 mC/m at 4.2 K. Complementary measurements on single crystals of SrTi03 and SrTi03.Nb reveal that the behavior of these SrTi03 thin Blms can be understood from the bulk properties with additional strong charge trapping at the film-substrate interface.

We have performed scanning tunneling microscopy ͑STM͒ in ultrahigh vacuum and transmission electron microscopy ͑TEM͒ on silver and gold clusters grown in preformed nanometer-sized pits on the surface of highly oriented pyrolytic graphite. We describe the preparation method and evaluate the three-dimensional shape of the clusters using a combination of STM and TEM applied to the same cluster sample. The nanometer-sized pits were essential to fix the clusters in position when using STM. The influence of the tip shape on the STM imaging of nanometer-sized clusters is discussed.

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