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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]

Highlights • Films of Ce 0.95 Yb 0.04 Er 0.01 O 2 , were grown by PLD on a single crystal silicon diode. • The up-conversion film grown for 2.3 J/cm2 delivers the highest device performance. • The relative power conversion efficiency of the device is 12.1/39.2% at 1/2.1 sun. • The external quantum efficiency is 7.2% when illuminated with 980 nm light. Abstract Co-doped CeO 2 thin films were grown from a bulk target with starting composition Ce 0.95 Yb 0.04 Er 0.01 O 2 by pulsed laser deposition (PLD) on a p+-n-n+ single crystal silicon diode. The PLD laser fluence was varied between 1.7 J/cm2 and 3.7 J/cm2. The device with the film grown for a laser fluence of 2.3 J/cm2 delivers the highest performance taking advantage of the up conversion (UC) effect provided by this film. Namely, the increase in the relative power conversion efficiency of the device is 12.1% and 39.2% for illumination under 1 and 2.1 sun, respectively, and its relative external quantum efficiency is 8.2% when illuminated with 980 nm light. The film grown for the optimum 2.3 J/cm2 fluence shows good target-film composition transfer and a granular morphology with a low roughness. The UC mechanism consists of efficient energy transfer between spatially separated Yb3+ and Er3+ ions, i.e. the absorption of infrared light photons by the Yb3+ ions (2 F 7/2 → 2 F 5/2 transition) is followed by a two-step energy transfer process to neighboring Er3+ ions and by their characteristic luminescent emissions ((2 H 11/2 , 4 S 3/2) → 4 I 15/2) and (4 F 9/2 → 4 I 15/2). [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) thin films were grown by pulsed laser deposition on two slightly different types of single crystal substrates, namely SrTiO 3 (STO) buffered with a thin layer of conductive SrRuO 3 (SRO) , and SrTiO 3 doped with 0.5% Nb (STON). Although self-poling effect was expected in both cases, due to the compressive strain imposed by the substrate, it was found that the pyroelectric response of as-grown samples is with about two orders of magnitude larger for the PZT film deposited on SRO/STO compared to the one deposited on STON substrate. In order to explain the finding, the electrical properties were investigated and it was found that the quantities involved in the equation giving the magnitude of the pyroelectric signal, namely dielectric constant and electrical resistivity, have about the same values Therefore, the different pyroelectric response in the as-grown samples was explained by different structure of ferroelectric domains induced by the different carrier concentration in the two substrates: 90° domains for PZT on SRO/STO and 180° domains for PZT on STON. It appears that the resistivity of the substrate and its ability to compensate the depolarization field affect the domain structure, with impact on the pyroelectric response, although the strain conditions are similar in both cases. The trying to increase the pyroelectric response for the PZT film deposited on STON substrate by applying a poling process was not successful, as the 180° domain structure restores shortly after removing the poling field. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance. [Copyright &y& Elsevier]