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We report the fabrication and modeling of a microelectromechanical system (MEMS) entirely made of crystalline oxides. A suspended SrTiO3 (001) microcantilever is employed as flexible substrate for the deposition of epitaxial transition-metal oxide (TMO) thin films. Tensile strain is generated at the upper surface of the SrTiO3 cantilever during its bending. Strain is thus transmitted to an overgrown TMO film by epitaxial lock with the SrTiO3 element. A strain-generator device for epitaxial TMO films is thus demonstrated and modeled by finite element methods. Evaluation of the applied strain and its distribution along microcantilevers of rectangular and triangular geometries is given.

We combine transport experiments, advanced ab initio calculations, and model analysis to determine the thermoelectric power in the two-dimensional electron gas formed at the paradigmatic oxide interface SrTiO3/LaAlO3. We demonstrate that contrary to popular expectation, quantum confinement does not enhance the thermoelectric power of the electron gas at this interface with respect to its corresponding three-dimensional case. Our analysis directly relates the thermopower behavior to band structure characteristics typical of the oxide heterostructure (i.e., on-site and intersite band splitting), furnishing general interpretive prescriptions to search for oxide heterostructures with improved thermoelectric capabilities.

We report a field effect device fully made of strontium titanate (STO). This perovskite-type material is very attractive for oxide electronics both for its notable dielectric properties as well as for its semiconducting properties in the doped state. We exploit both of these properties by developing a field effect device in which oxygen deficient STO acts as a conducting channel and stoichiometric STO as a dielectric barrier. Such a barrier is obtained by electrochemical oxidation of the surface of an oxygen deficient semiconducting STO film, deposited by pulsed laser ablation in ultrahigh vacuum conditions. The channel conductivity is varied by the application of an electric field between the channel itself and a metallic gate deposited onto the dielectric barrier. Modulation capability of more than 60% is achieved by applying potential lower than 1 V. Conductivity changes are due to electrostatic induced variations of the charge carrier density (n). This result is confirmed by Hall effect measurements during gate biasing. The very good agreement of the measured n with the value calculated from the device capacitance proves the electrostatic origin of the effect observed.

Superconducting thin films of MgB2 were deposited by Pulsed Laser Deposition on magnesium oxide and sapphire substrates. Samples grown at 450C in an argon buffer pressure of about 10-2 mbar by using a magnesium enriched target resulted to be superconducting with a transition temperature of about 25 K. Film deposited from a MgB2 sintered pellet target in ultra high vacuum conditions showed poor metallic or weak semiconducting behavior and they became superconducting only after an ex-situ annealing in Mg vapor atmosphere. Up to now, no difference in the superconducting properties of the films obtained by these two procedures has been evidenced.

Superconducting multilayers, whose growth and structure are determined by the kinetic deposition and not by thermodynamics, are a powerful tool for investigating High T c superconductors (HTSC) properties and for possible future applications. By means of Pulsed Laser Deposition (PLD), we grew such materials alternating infinite layer phases both pure and doped, to supply CuO 2 planes and charge reservoir (CR) blocks respectively. We found out that using CR chemically doped with high concentrations of Ag and Sc substituted on the copper site in infinite layer compounds leads to a semiconducting behavior, whereas oxygen doping seems to be much more effective, since the BaCuO 2 infinite phase, grown in high oxygen partial pressure, does actually bring about a superconducting behavior. We deposited BaCuO 2 /CaCuO 2 superlattices with various periodicities and studied their transport and structural properties. By varying the deposition parameters, we reached both kinetic and thermodynamic growth and we observed semiconducting and superconducting behaviors.

We investigated the room-temperature current-voltage characteristics of Au/Nb:SrTiO3 Schottky junctions under various atmospheres and working pressures. We observed that oxygen partial pressure reversibly modulates junction response, briefly individual specimens behave as high-quality rectifiers in oxygen-rich atmospheres and as bipolar resistive switches in vacuum and inert gases. A two orders of magnitude modulation of resistance switching characterizes samples with the highest content of interfacial oxygen vacancies. We attribute this behavior to oxygen ionosorption and chemical oxidation at the metal-oxide interface. Our results are relevant to oxide devices displaying resistive switching at ambient-exposed interfaces, and might be exploited for gas detection purposes.