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We present the conduction mechanisms of Ba2/3Sr1/3TiO3 thin films integrated in metal-insulatormetal (MIM) capacitors and the modelling of the frequency-dependent electrostrictive resonances (in the 100 MHz-10 GHz domain) induced in the devices upon applying different voltage biases. Au/BST/Ir MIM structures on MgO substrates have been fabricated and, depending on their specific polarization, we highlighted different conduction mechanisms in the devices. Depending on the dc bias polarity, the conduction current across the material shows a space-charge-limited-current behavior under negative polarization, whereas under positive bias, the conduction obeys an electrode-limited Schottky-type law at the Au/BST interface. The application of an electric field on the device induces the onset of acoustic resonances related to electrostrictive phenomena in the ferroelectric material. We modeled these acoustic resonances over a wide frequency range, by using a modified Lakin model, which takes into account the dispersions of acoustic properties near the lower electrode/thin film interface. [ABSTRACT FROM AUTHOR]

The growth and thermal stability of textured iridium thin films used as bottom electrode in electronic devices based on ferroelectric materials were investigated. The thin films were grown using the dc magnetron sputtering technique. The Ir layers directly deposited on SiO/Si substrates present a mixed (111) and (200) orientations, while the films grown on Ti seed layers exhibit a strong preferred (111) orientation favoured by good matching with the titanium lattice. The substrate temperature during the growth of iridium/titanium stack has a significant effect on the surface morphology of the iridium layer and its thermal stability. The as-grown surface of 20-nm-thick Ir films is smooth, having a root-mean-square (rms) roughness of 0.7 nm. After thermal annealing the Ir film shows an increased surface roughness due to the formation of agglomerations. The change in the surface morphology of the Ir layer is due to titanium diffusion and its oxidation. Thicker and better crystallised iridium thin films annealed in oxygen atmosphere at 700 °C show a good thermal stability with only a slight modification of the surface morphology. Within the limits of experimental error, there is no change in the electrical resistivity before and after thermal annealing. The rms roughness has not varied significantly and the XPS investigation shows no traces of titanium oxide on iridium surface. Ir/Ti stack deposited under the optimum conditions could be successfully used as electrode in devices based on oxide thin films. [ABSTRACT FROM AUTHOR]

Abstract: Ba(X1/3Ta2/3)O3 (X=Mg, Zn) thin films were grown on commercial Pt-coated Si substrates by radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD) method. Single phase Ba(Mg1/3Ta2/3)O3 and Ba(Zn1/3Ta2/3)O3 ceramic targets having an ordered hexagonal structure (with space group) were used for deposition. Structural, morphological and surface characterizations of the Ba(X1/3Ta2/3)O3 (BXT) films were performed using X-ray diffraction, scanning electron microscopy and atomic force microscopy. X-ray diffraction studies evidenced a cubic (disordered) perovskite structure, with unit cell typical for Pm3m space group. Scanning electron microscopy investigations showed that BXT films have a columnar microstructure, which is oriented perpendicular to the substrate. The temperature dependence of the dielectric permittivity of the films was recorded at 100kHz. Unlike targets, the BXT films exhibit positive values of the temperature coefficient of the dielectric permittivity. BaMg1/3Ta2/3O3 and BaZn1/3Ta2/3O3 thin films with dielectric constant of about 22.5 and 25, respectively have been obtained. [Copyright &y& Elsevier]

Abstract: Ba(Zn1/3Ta2/3)O3 (BZT) thin films were grown on Pt-coated Si substrates at 500°C substrate temperatures by pulsed electron beam deposition method and post-annealed at 600 and 650°C for 1h. The X-ray diffraction patterns indicate that the as-grown films are partially crystallized but single-phase cubic perovskite structure was formed in annealed films. The temperature dependence of the dielectric constant of the BZT films was recorded in the −100 to +100°C range. The annealing treatment induces a decrease of the temperature coefficient of the dielectric permittivity with an order of magnitude, from 2000 to 100ppm/°C. The influence of the annealing treatments on the temperature behavior of the BZT films was evidenced; a dielectric constant of about 21 at room temperature was obtained for the films annealed at 650°C. [Copyright &y& Elsevier]

Ba0.6Sr0.4TiO3 (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition (PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with size of spherical grains up to 150 nm. The capacitance–voltage (C–V) characteristics of the BST films were performed by applying a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been measured at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Single-phase Ba(Mg1/3Ta2/3)O3 thin films were prepared by radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD) starting from a bulk ceramic target synthesized by solid state reaction. Atomic force microscopy, X-ray diffraction and spectroscopic ellipsometry were used for morphological, structural and optical characterization of the BMT thin films. The X-ray diffraction spectra show that the films exhibit a polycrystalline cubic structure. From spectroscopic ellipsometry analysis, the refractive index varies with the thin films deposition parameters. By using the transmission spectra and assuming a direct band to band transition a band gap value of ≈4.72eV has been obtained. [Copyright &y& Elsevier]

Abstract: Barium strontium titanate (BST) bulk ceramic with composition Ba0.5Sr0.5TiO3 was produced by solid-state reaction and was used as target for PLD thin film deposition. A Nd-YAG laser, working at 5–10Hz and different wavelengths has been used. Thin films of stoichiometric BST were deposited on alumina substrate with the thickness between 400 and 500nm. An aditional annealing was carried out at 800°C for 6h. XRD and SEM were used for sample characterization. Capacity measurements were performed versus temperature at 100kHz in a large temperature range. A diffuse ferroelectric–paraelectric phase transition with T C =−72°C for the BST thin film was determined. A 5% tunability was measured in the transition region. [Copyright &y& Elsevier]

Abstract: Thin films of zirconium tin titanate, (Zr0.8Sn0.2)TiO4 (ZST) were deposited using a pulsed electron beam source based on a channel-spark discharge for target ablation. An advanced degree of crystallization was obtained for the films deposited on alumina substrate post-annealed at 1000°C. The crystalline lattice constants of the films are very close to those of the target material, which confirms the same stoichiometry in ZST films and in the bulk. [Copyright &y& Elsevier]