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

11th International Conference on Photo-Excited Processes and Applications

September 10-14, 2018
Vilnius, Lithuania
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2018 E-MRS Fall Meeting and Exhibit

September 18-21, 2018
Warsaw, Poland
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Upcoming Group Seminars

TBA
Speaker: B. Biswas
Date: Monday 1 October 2018 16:00
Room: OFLG/402, TFI

Interface effects on the ionic conductivity of doped ceria – yttria-stabilized zirconia heterostructures
Speaker: Daniele Pergolesi
Date: Tuesday 2 October 2018 13:00
Room: OSGA/EG06, LMX

TBA
Speaker: N. Ohannesian
Date: Monday 15 October 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

Jikun Chen, Max Döbeli, Alexander Wokaun, and Thomas Lippert
Plasma interactions with the N2O background gas: Enhancing the oxidization of alkaline-earth species for pulsed laser deposition
Journal of Applied Physics 124, 085308 (2018)


29 August 2018

Plasma interactions with the N2O background gas: Enhancing the oxidization of alkaline-earth species for pulsed laser deposition

Abstract:
Ratio of MO<sup>+</sup>/(M<sup>+</sup> + MO<sup>+</sup>) vs. dissociation energy of MO<sup>+</sup> species as determined at pN<sub>2</sub>O of (a) 1 × 10<sup>−2</sup> mbar and (b) 1.5 × 10<sup>−1</sup> mbar, over a large variety of laser induced plasma species elements. The MO<sup>+</sup>/(M<sup>+</sup> + MO<sup>+</sup>) shown for a metallic element is the average value from different oxide targets, and the error bar represents their standard derivation. From Figure 3zoom
Ratio of MO+/(M+ + MO+) vs. dissociation energy of MO+ species as determined at pN2O of (a) 1 × 10−2 mbar and (b) 1.5 × 10−1 mbar, over a large variety of laser induced plasma species elements. The MO+/(M+ + MO+) shown for a metallic element is the average value from different oxide targets, and the error bar represents their standard derivation. From Figure 3
Using N2O as an alternative background gas to O2 when growing oxide thin films by pulsed laser deposition (PLD) was previously expected to result in larger oxygen contents of as-grown thin films. In this work, we investigate the composition and kinetic energy of the pulsed laser induced plasmas that propagated in N2O and O2 by using mass spectrometry and plasma imaging. Two distinguished features were observed when using N2O instead of O2. (1) In N2O background gas as compared to O2, a larger proportion of negative oxygen ions was detected. (2) The alkaline-earth elements were fully oxidized in the N2O background, which is not achievable in O2. These observations are attributed to the smaller dissociation energy of the N2O molecules as compared to O2. The smaller dissociation energy of the background gas molecule is expected to reduce the interaction strength during their central collisions with the plasma species. As a result, the dissociable or electron detachable plasma species can be formed in larger amounts in N2O background, compared to O2. Comparing the composition of the deposited thin films indicates a larger oxygen content of the film grown in N2O background gas, as compared to O2, at pressures of ∼10−1 mbar, which is the most commonly used deposition pressure in PLD. Nevertheless, this was not achieved when performing PLD at ∼10−2 mbar, since the pressure was not high enough to trigger the formation of the shockwave front during the plasma expansion and thereby the lightest oxygen plasma species were preferentially scattered.
Keywords: pulsed laser deposition; plasma spectroscopy; composition; plasma species;

Facility: Thin Films and Interfaces, LMX, ETHZ

Reference: J. Chen et al., J. Appl. Phys., 124, 085308 (2018)

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