Browsing by Author "Holgado, S."
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Item Open Access Fabrication of continuous ultrathin ferroelectric films by chemical solution deposition methods(Materials Research Society, 2008-10) Ricotea, J.; Holgado, S.; Huang, Zhaorong; Ramos, P.; Fernandez, R.; Calzada, M. L.The integration of ferroelectrics in nanodevices requires firstly the preparation of high-quality ultrathin films. Chemical solution deposition is considered a rapid and cost-effective technique for preparing high-quality oxide films, but one that has traditionally been regarded as unsuitable, or at least challenging, for fabricating films with good properties and thickness below 100 nm. In the present work we explore the deposition of highly diluted solutions of pure and Ca-modified lead titanates to prepare ultrathin ferroelectric films, the thickness of which is controlled by the concentration of the precursor solution. The results show that we are able to obtain single crystalline phase continuous films down to 18 nm thickness, one of the lowest reported using these methods. Below that thickness, the films start to be discontinuous, which is attributed to a microstructural instability that can be controlled by an adequate tailoring of the processing conditions. The effect of the reduction of thickness on the piezoelectric behavior is studied by piezoresponse force microscopy. The results indicate that films retain a significant piezoelectric activity regardless of their low thickness, which is promising for their eventual integration in nanodevices, for example, as transducer elements in nanoelectromechanical systems.Item Open Access Use of the solvent chemistry for the control of the critical thickness of PbTiO3 ultrathin films(Mrs Materials Research Society, 2010-05-31T00:00:00Z) Fernandez, R.; Holgado, S.; Huang, Zhaorong; Calzada, M. L.; Ricote, J.The preparation of high-quality ferroelectric PbTiO3-based ultrathin films by chemical solution deposition. using a diol-based sol-gel method, has proved to be successful. However, there is a critical thickness below which the films break up into isolated structures According to previous studies, above a certain grain size to thickness ratio a microstructural instability occurs and the coatings are no longer continuous. We explore the use of the solvent chemistry to control this phenomenon, as an alternative to the more conventional variation of the crystallization parameters. The use of diols with short C chain lengths leads to films with smaller gram sizes, whose critical thicknesses are lower. A reduction from 40 to 15 nm is achieved by reducing the number of C of the chol used from 5 to 2. A critical value of G/t < 5.0 is necessary to obtain continuous ultrathin films with the processing conditions used