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Sr(Ti1-x ,Ru x )O3 (STRO) epitaxial thin films were deposited on single-crystal SrTiO3(100) substrates using the inductive-coupling-plasma-induced RF magnetron sputtering method without oxygen. The electrical conductivity of STRO films increases with Ru concentration and levels of the Ru 4d states are observed in the band gap of SrTiO3 by X-ray photoelectron spectroscopy (XPS) analysis. These results are consistent with those obtained by first-principles calculations. Thermodynamic stability increases with the decrease of Ru concentration, and STRO (x2 atmosphere at 600°C. This high resistance against reductive processes indicates that STRO (x

Ferroelectric properties were investigated using SrRuO3/(Ba x , Sr1-x )TiO3(BSTO)/SrRuO3 all-perovskite heteroepitaxial capacitors on strontium titanate substrates. The dielectric film had a composition with a Ba content of x=0 to 1, i.e., the whole composition of the SrTiO3–BaTiO3 solid-solution system. The c-axis of the BSTO film was elongated depending on the Ba content, and reached 0.441 nm at the BaTiO3 composition, which was 8.6% larger than the bulk c-axis. A peak relative dielectric constant of 870 and maximum remanent polarization (2P r) of 58 µC/cm2 were obtained depending on the Ba content at a dielectric thickness of 20 nm. These are the highest storage capacitance capacitor and the thinnest ferroelectric capacitor reported so far. Possibilities for deep submicron ferroelectric and dielectric memory applications are also discussed.

Epitaxial titanium aluminum nitride, Ti1-x Al x N(100) (0≦x2 + ion beam irradiation with 100 eV energy and Ti and Al simultaneous evaporation. The epitaxial relationship was confirmed to be Ti1-x Al x N(100)//Si(100), Ti1-x Al x N//Si by X-ray diffraction (XRD) and in situ reflection high-energy electron diffraction (RHEED). Although the electrical resistivity increased exponentially with x, the values remained on the order of 10-4 Ω·cm. Using the Ti1-x Al x N buffer layer, we have successfully fabricated a capacitor with an epitaxial (Ba, Sr)TiO3 film on a Si substrate.

Asymmetric ferroelectricity and conduction of anomalous leakage current were observed in heteroepitaxial BaTiO3 thin films grown by rf magnetron sputtering at 600° C on three different electrode/substrate combinations: SrRuO3/SrTiO3, Pt/MgO and Nb doped SrTiO3. The voltage shift of hysteresis loops of the capacitance was a linear function of the thickness of the BaTiO3 films and became as large as 10 V in the film with a thickness of 410 nm. The asymmetry did not disappear even after a heat treatment carried out at 800° C in air. On the other hand, a steep increase in the leakage current was observed in the heteroepitaxial films when a positive voltage was applied. The origin of both the asymmetric hysteresis and the anomalous conduction is discussed in terms of asymmetric crystal structure caused by misfit dislocations introduced in heteroepitaxial growth.

Heteroepitaxial Ba0.6Sr0.4TiO3 thin films with thicknesses from 26 nm to 97 nm were grown on SrRuO3 bottom electrode films on SrTiO3 single crystal substrates. Although the films have a paraelectric composition, ferroelectric hysteresis was observed in displacement versus electric field (D–E) loops. The ferroelectricity is considered to be developed as a result of bi-axial stress, caused by lattice mismatch between the dielectric films and the bottom electrodes. The maximum difference in the displacement was over 0.4 C/m2, even when the thickness of the film was reduced to 26 nm. The hysteresis loops showed an asymmetric characteristic at a polarity of applied voltage. The asymmetry was discussed in terms of an asymmetrical deformation of the crystal structure, which is probably introduced during the heteroepitaxial growth.

Epitaxial TiN(111) films were grown on Si(111) substrates by low energy reactive ion beam deposition using N2 ion beam irradiation and Ti evaporation. TiN epitaxial film formation was investigated as a function of the substrate temperature (T s) and the kinetic energy of the ion beam (E b). Using X-ray diffraction (XRD) and in-situ reflection high-energy electron diffraction (RHEED), the epitaxial relationship was found to be TiN(111)|| Si(111), TiN|| Si above substrate temperature of 400° C. Cross-sectional bright-field transmission electron microscope (TEM) observation has shown that the interface is quite flat and sharp and that four TiN lattice spacings match three spacings of the Si lattice. A lowest resistivity value of 18 µΩ· cm (T s=600° C, E b=100 eV) was obtained.

Reactive ion beam epitaxy with an extra-low energy N2 + ion beam and a Ti molecular beam has been employed to grow hetero-epitaxial TiN films on MgO substrates. The TiN film quality drastically depends on the N2 + kinetic energy. Epitaxial TiN films with a low resistivity about 16 µΩ·cm were obtained at a kinetic energy of 50 eV/atom even at room substrate temperature, which is the lowest epitaxial temperature so far. At an elevated temperature, epitaxial growth was observed at a wide kinetic energy range. Epitaxial growth mechanisms in low energy reactive ion beam deposition are discussed.