The Thin Films and Interfaces GroupThin films are nowadays utilized in many applications, ranging from semiconductor devices to optical coatings and are even present in pharmaceuticals (polymers). This wide-spread application of films with thicknesses from atomic monolayers to microns is due to the developments of thin film deposition techniques. Thin films are also important for studies of materials with new and unique properties due to the possibility of tuning their crystallographic and morphological properties. The thin film approach, i.e. the presence of interfaces (to a substrate or the film surface) adds more degrees of freedom for influencing the properties of materials, e.g. by lattice strain or surface functionalization. For these fundamental studies of material properties large research facilities such as synchrotron radiation or neutron spallation sources are one of the keys that the Paul Scherrer Institute (PSI) provides.
Our group focuses on the preparation of highly defined thin films by pulsed laser deposition (PLD) for applications in energy technology, but also for new properties, such as multiferroicity. We are working on the fundamental understanding of the PLD process, the influence of strain on material properties and we utilize the large facilities at PSI (neutrons, muons, and photons from the SLS). We therefore cooperate with many groups within the NUM, ENE and SYN divisions, and offer in addition a thin film deposition service.
Boston, Massachusetts, USA
Speaker: F. Haydous
Date: Monday 24 October 2016 16:30
Speaker: A. Ojeda Gonzalez-Posada
Date: Thursday 27 October 2016 11:00
Speaker: C. W. Schneider
Date: Tuesday 08 November 2016 9:00
Tuning the Surface Electrochemistry by Strained Epitaxial Pt Thin Film Model Electrodes Prepared by Pulsed Laser Deposition
Adv. Mater. Interfaces 3, 1600222 (2016)
A novel approach for tailoring strained Pt model electrocatalysts using pulsed laser deposition is presented. The physical properties of Pt films grown on single-crystalline (100)- and (111)-oriented strontium titanate depend significantly on the various deposition parameters (e.g., fluence, temperature, background atmosphere, postannealing, and number of process steps), as revealed by scanning electron microscopy and X-ray studies. By properly selecting the deposition conditions, thin, epitaxial, and strained (100)- and (111)-oriented Pt films suitable as model electrodes can be prepared. Cyclic voltammetry measurements indicate that the strain in the Pt films changes significantly the Pt surface properties, such as the hydrogen underpotential deposition (Hupd ) features. CO oxidation experiments demonstrate that the strain affects strongly also the position of the CO oxidation peak shifting it to more positive potentials. This might be attributed to a modification of the adsorption behavior of oxygenated species on the strained interface. This research clearly highlights the potential of using as-produced Pt film as model catalysts to study the effect of strain on electrocatalytic reactions while minimizing possible side effects connected to the common preparation methods for strained Pt catalysts, such as alloy formation, alloy leeching, or conductive support contributions. Link
Morphology of thin Pt films prepared by the different strategies illustrated in Figure S3 (Supporting Information). A) Increasing the thickness to 12 nm let to percolated network morphology, independent of the pretreatment of the STO substrate. B) Introducing a background atmosphere clearly changed the morphology to separated Pt islands, with Island sizes dependent on the background gas. C) Postannealing process evidently let to a dewetting of the Pt film.