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

News


15 November 2018

Woman in Science

Congratulations to our former postdoc, Alexandra Palla-Papavlu (4th from the left), for winning the L’Oreal Prize for Woman in Science in the category Physics in Romania
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Upcoming Conference

April 2019

2019 MRS Spring Meeting & Exhibit

April 22-26, 2019
Phoenix, Arizona, USA
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May 2019

2019 E-MRS Spring Meeting and Exhibit

May 27-31, 2019
Nice, France
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8th International Congress on Laser Advanced Materials Processing

LPM2019 - The 20th International Symposium on Laser Precision Microfabrication
HPL2019 – The 8th International Symposium on High Power Laser Processing
May 21-24, 2019
Hiroshima, Jp
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Upcoming Group Seminars

TBA
Speaker: S. Gürakar
Date: Monday 21 January 2019 16:00
Room: OFLA/002, TFI

TBA
Speaker: L. Indrizzi
Date: Monday 11 February 2019 16:00
Room: OFLG/402, TFI

Scientific Highlight

25 October 2018

Rolling dopant and strain in Y-doped BiFeO3 epitaxial thin films for photoelectrochemical water splitting

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We report significant photoelectrochemical activity of Y-doped BiFeO3 (Y-BFO) epitaxial thin films deposited on Nb:SrTiO3 substrates. The Y-BFO photoanodes exhibit a strong dependence of the photocurrent values on the thickness of the films, and implicitly on the induced epitaxial strain. The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. The crystalline coherence breaking due to the small ionic radius Y-addition was analyzed using Willliamson-Hall approach on the 2Θ-ω scans of the symmetric (00l) reflections and confirmed by high resolution TEM (HR-TEM) analysis. In the thinnest sample the lateral coherence length (L||) is preserved on larger nanoregions/nanodomains. For higher thickness values L|| is decreasing while domains tilt angles (αtilt) is increasing. The photocurrent value obtained for the thinnest sample was as high as Jph = 0.72 mA/cm2, at 1.4 V(vs. RHE). The potentiostatic scans of the Y-BFO photoanodes show the stability of photoresponse, irrespective of the film’s thickness. There is no clear cathodic photocurrent observation for the Y-BFO thin films confirming the n-type semiconductor behavior of the Y-BFO photoelectrodes.
Reference: F. Haydous et al, Scientific Reports 8, 15826 (2018)

Read full article: here


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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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.

Most recent Paper

Alejandro Ojeda-G-P, Xiang Yao, Nadezhda M. Bulgakova, Alexander V. Bulgakov, Thomas Lippert;
A dynamic double layer as the origin of the mass-dependent ion acceleration in laser-induced plasmas
Applied Physics A (2019)



4 December 2018

A dynamic double layer as the origin of the mass-dependent ion acceleration in laser-induced plasmas

Abstract:
Schematics of DL evolution and ion acceleration in a pulsed laser plume, demonstrating the mechanism responsible for higher kinetic energies of heavier ions. a The DL develops in the beginning of expansion of the laser-ablation plume in its front where electrons have much higher velocity than ions and atoms escape from the plume into vacuum. The resulting charge separation leads to generation of the electric field in the front of the plume, while the plume core remains quasi-neutral (marked as QNPC). b With time, light ions gain high velocities in the ambipolar double-layer field and leave behind heavier ones. As a result, the heavier ions remain in the region of the ambipolar field with the higher intensity for a longer time, thus, possessing a higher energy from the DL. The enrichment of the axis with heavier ions/neutrals as a result of off-axis scattering of lighter ions (in accordance with Ref. [28]) was also observed by MS but was slightly masked by the different ionization energies. From Fig. 1zoom
Schematics of DL evolution and ion acceleration in a pulsed laser plume, demonstrating the mechanism responsible for higher kinetic energies of heavier ions. a The DL develops in the beginning of expansion of the laser-ablation plume in its front where electrons have much higher velocity than ions and atoms escape from the plume into vacuum. The resulting charge separation leads to generation of the electric field in the front of the plume, while the plume core remains quasi-neutral (marked as QNPC). b With time, light ions gain high velocities in the ambipolar double-layer field and leave behind heavier ones. As a result, the heavier ions remain in the region of the ambipolar field with the higher intensity for a longer time, thus, possessing a higher energy from the DL. The enrichment of the axis with heavier ions/neutrals as a result of off-axis scattering of lighter ions (in accordance with Ref. [28]) was also observed by MS but was slightly masked by the different ionization energies. From Fig. 1
The kinetic energies of the plasma plume species and their control are critical to ensure the high quality of thin films grown by pulsed laser deposition. The maximum kinetic energies of ionic plasma species from different multicomponent materials, CaTiO3, EuAlO3, La0.4Ca0.6MnO3, La0.4Ca0.6Mn0.9Ru0.1O3, and YBa2Cu3O7-x, have been analysed, revealing a wide range of energies of 100–700 eV. A direct relationship between the maximum kinetic energies and atomic masses has been found: the larger is the mass of an ion, the higher is its energy. This dependence varies with the kind of the ablated material and its slope is changing with laser fluence. The results are explained by the generation of a self-consistent ambipolar electric field in front of the expanding laser plume. The concept of a dynamic double layer has been considered, when heavier ions remain in the ambipolar field for a longer time as compared to lighter ions, thus resulting in stronger acceleration of heavy ions.
Keywords: Pulsed laser deposition; Laser induced plasma; Double layer; Plasma plume expansion;

Facility: Thin Films and Interfaces, LMX, HiLASE Centre, Institute of Physics ASCR, Czech Republic, S. S. Kutateladze Institute of Thermophysics SB RAS, Russia

Reference: A. Ojeda et al., Applied Physics A (2019), online publication 05. 01. 2019

Read full article: [here]
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