We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF₂(001) substrate. High critical current density values – larger than 1 MA/cm² in self field and liquid helium – are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through transmission electron microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what was observed on SrTiO₃, where defects parallel to the c-axis enhance pinning in that direction.

By applying a negative voltage to the conducting tip of an atomic force microscope, we modify on submicron-scale semiconducting oxygen deficient ${\mathrm{SrTiO}}_{\text{3−δ}}$ thin films grown on ${\mathrm{LaAlO}}_3$ substrates. In comparison with the as-grown film, the modified regions present different electrical and structural properties, which can be exploited to realize submicrometer circuits. After a discussion on the mechanisms of the process, we report a prototype of a ${\mathrm{SrTiO}}_{\text{3−δ}}$ -based sidegate field-effect transistor, showing a 4% modulation of channel resistivity with gate voltages up to 40 V.

Using high-quality epitaxial $c$ -axis $\mathrm{Pb}\left({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}\right){\mathrm{O}}_3$ films grown by off-axis magnetron sputtering onto metallic (001) $\mathrm{Nb}$ -doped ${\mathrm{SrTiO}}_3$ substrates, a nonconventional thin-film surface acoustic wave device based on periodic piezoelectric transducers was realized. The piezoelectric transducers consist of a series of ferroelectric domains with alternating polarization states. The artificial modification of the ferroelectric domain structure is performed by using an atomic force microscope tip as a source of electric field, allowing local switching of the polarization. Devices with 1.2 and $0.8\mu \mathrm{m}$ wavelength, defined by the modulation period of the polarization, and corresponding to central frequencies in the range $1.50–3.50\mathrm{GHz}$ have been realized and tested.

We explored the feasibility of employing strontium titanate $({\mathrm{SrTiO}}_{\mathrm{3}})$ as semiconducting material in field-effect metal–insulator–semiconductor epitaxial heterostructures. This idea was suggested by the observation of a dramatic effect of the oxygen deficiency on ${\mathrm{SrTiO}}_{\text{3−δ}}$ transport properties, which brings about metallic behavior with low-temperature mobility values comparable with those commonly found for silicon. By pulsed-laser deposition, we realized patterned field-effect devices, showing a resistance enhancement up to 90%. This promising result could open perspectives for crystalline-oxide electronics.