Paul Scherrer Institute

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The Thin Films and Interfaces Group

Thin 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. Read more Top

PhD projects at the Thin Films and Interfaces Group

At present, we do not have open PhD positions available. As soon as we have details will be posted at our open position page. Other open positions are always published on the PSI Open Positions page.

News

Upcoming Conference

2018 E-MRS Spring Meeting and Exhibit

June 18-22, 2018
Strasbourg, France
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19th International Symposium on Laser Precision Microfabrication

June 25-28, 2018
Edinburgh, UK
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Upcoming Group Seminars

Novel Functionalities in Atomically Controlled Oxide Heterostructures by Pulsed Laser Deposition - Abstract
Speaker: Prof. Dr. Ing. Guus Rijnders
Faculty of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
Date: Monday 7 May 2018 16:00
Room: OFLG/402, LMX SEMINAR

TBA
Speaker: Hanu Arava
Date: Tuesday 8 May 2018 13:00
Room: OSGA/EG06, LMX

TBA
Speaker: F. Haydous
Date: Monday 21 May 2018 16:00
Room: OFLG/402, TFI

Special interview with Prof. Thomas Lippert (PSI and Principle Investigator at I2CNER, Kyushu University) and Prof. Tatsumi Ishihara (Associate Director I2CNER, Kyushu University) on Current and Future Energy Research and Development in Europe: Perspectives from Switzerland, Germany and Japan. The interview is being published in the August 2017 issue of the Energy Outlook of the International Institut for Carbon-Neutral Energy Research, I2CNER.
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Most recent Paper

Aline Fluri, Daniele Pergolesi, Alexander Wokaun, and Thomas Lippert
Stress generation and evolution in oxide heteroepitaxy
Phys. Rev. B 97, 124412 (2018)


16 March 2018

Stress generation and evolution in oxide heteroepitaxy

Abstract:
Substrate curvature and stress measurements. The curvature evolution with time (a) and the stress evolution with thickness (b) is shown for growth of different oxide materials. The data in (b) is calculated from the Stoney equation, i.e., the average stress of the film during the growth process. The samples are labeled in the legend as film-(buffer layer-)substrate and are listed in the order cases 1–6. A vertical line indicates in (a) where the growth was stopped. Films of BZC, STO, and SDC were grown on single-crystalline substrates. Films of BZC, BZY, and SDC were grown on epitaxial buffer layers.zoom
Substrate curvature and stress measurements. The curvature evolution with time (a) and the stress evolution with thickness (b) is shown for growth of different oxide materials. The data in (b) is calculated from the Stoney equation, i.e., the average stress of the film during the growth process. The samples are labeled in the legend as film-(buffer layer-)substrate and are listed in the order cases 1–6. A vertical line indicates in (a) where the growth was stopped. Films of BZC, STO, and SDC were grown on single-crystalline substrates. Films of BZC, BZY, and SDC were grown on epitaxial buffer layers.
Many physical properties of oxides can be changed by inducing lattice distortions in the crystal through heteroepitaxial growth of thin films. The average lattice strain can often be tuned by changing the film thickness or using suitable buffer layers between film and substrate. The exploitation of the full potential of strain engineering for sample or device fabrication rests on the understanding of the fundamental mechanisms of stress generation and evolution. For this study an optical measurement of the substrate curvature is used to monitor in situ how the stress builds up and relaxes during the growth of oxide thin films by pulsed laser deposition. The relaxation behavior is correlated with the growth mode, which is monitored simultaneously with reflection high-energy electron diffraction. The stress relaxation data is fitted and compared with theoretical models for stress evolution which were established for semiconductor epitaxy. The initial stage of the growth appears to be governed by surface stress and surface energy effects, while the subsequent stress relaxation is found to be fundamentally different between films grown on single-crystal substrates and on buffer layers. The first case can be rationalized with established theoretical models, but these models fail in the attempt to describe the growth on buffer layers. This is most probably due to the larger average density of crystalline defects in the buffer layers, which leads to a two-step stress relaxation mechanism, driven first by the nucleation and later by the migration of dislocation lines.
Keywords: pulsed laser deposition; thin films; strain; simulations;

Facility: Thin Films and Interfaces, LMX, ETHZ, University of Kyushu

Reference: A. Fluri et al., Phys. Rev. B 97, 124412 (2018)

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