The Thin Films and Interfaces Group

Yi Hu

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.

Interfaces
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TFI goes TecDays

In July 2022, two PhDs of our Thin Films and Interfaces (TFI) Group offered a practical teaching module to pupils at the Kantonsschule Stadelhofen as part of the Swiss TecDays. These are one-day events at Swiss grammar schools, organized by the Schweizerische Akademie der Technischen Wissenschaften (SATW), to support and strengthen technology education at schools. By bringing together pupils and experts from industry, universities, or research institutions, TecDays aims to raise an early awareness for technology and science.

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TFI SEMINAR
Date:  Monday 9 September, 2024, 16:00 
Title: TBA
Speaker:  Xiaochun Huang  
Room: OFLG/402 

Literature meeting
Date:  Monday 16 September, 2024, 16:00 
Speaker:  Daniele Pergolesi & Kyle Stephens     
Room: OFLG/401

TFI SEMINAR
Date: Monday 23 September, 2024, 16:00 
Title: TBA
Speaker:  Nick Shepelin     
Room: OFLG/402

LMX SEMINAR: 
Date:  Friday 27 September 2024, 13:00 
Speaker:  Soohyeon   
Room: OSGA/EG06 

All Seminars
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September 2024

iWOE-30 2024 

International Workshop on Oxide Electronics
September 29.-2.October 2024 , Darmstadt, Germany
More Information

August 2024

International Mass Spectrometry Conference 2024 

Aug. 17-23, 2024
Melbourne, Australia
More Information will be provided here

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Highlights_2
Huang et al

Surface oxidation/spin state determines oxygen evolution reaction activity of cobalt-based catalysts in acidic environment

Co-based catalysts are promising candidates to replace Ir/Ru-based oxides for oxygen evolution reaction (OER) catalysis in an acidic environment. However, both the reaction mechanism and the active species under acidic conditions remain unclear. In this study, by combining surface-sensitive soft X-ray absorption spectroscopy characterization with electrochemical analysis, we discover that the acidic OER activity of Co-based catalysts are determined by their surface oxidation/spin state. 

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A practical guide to pulsed laser deposition

A practical guide to pulsed laser deposition

Nanoscale thin films are widely implemented across a plethora of technological and scientific areas, and form the basis for many advancements that have driven human progress, owing to the high degree of functional tunability based on the chemical composition. Pulsed laser deposition is one of the multiple physical vapour deposition routes to fabricate thin films, employing laser energy to eject material from a target in the form of a plasma ...

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Momentum-resolved electronic structure of LaTiO2N photocatalysts by resonant Soft-X-ray ARPES

Oxynitrides are promising materials for visible light-driven water splitting. However, limited information regarding their electron-momentum resolved electronic structure exists. Here, with the advantage of the enhanced probing depth and chemical state specificity of soft-X-ray ARPES, we determine the electronic structure of the photocatalyst oxynitride LaTiO2N and monitor its evolution as a consequence of the oxygen evolution reaction. After the photoelectrochemical reactions, we observe a partial loss of Ti- and La-N 2p states, distortions surrounding the local environment of titanium atoms and, unexpectedly, an indication of an electron accumulation layer at or near the surface, which may be connected with either a large density of metallic surface states or downward band bending. The distortions and defects associated with the titanium 3d states lead to the trapping of electrons and charge recombination, which is a major limitation for the oxynitride LaTiO2N. The presence of an accumulation layer and its evolution suggests complex mechanisms of the photoelectrochemical reaction, especially in cases where co-catalysts or passivation layers are used.

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Special interview with Prof. Thomas Lippert and Prof. Tatsumi Ishihara

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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Student projects at the Thin Films and Interfaces Group

Most of the time we have student projects related to the work we do. Just talk to us if you are interested in something we are working on not advertised on our pages.

Currently, we are looking for a Semester or Master Student on the topic of ferroelectric field effect transistors (FeFETs).

If anyone is interested, please contact Prof. Dr. Thomas Lippert (thomas.lippert@psi.ch) or Dr Nikita Shepelin (nikita.shepelin@psi.ch).

At present, we have no open PhD positions available. Other open positions are always published on the PSI Open Positions page.

Bosse JACS 2024

Molecular O2 Dimers and Lattice Instability in a Perovskite Electrocatalyst

Jan Bosse, Jian Gu, Jaewon Choi, Vladimir Roddatis, Yong-Bin Zhuang, Nagaarjhuna A. Kani, Anna Hartl, Mirian Garcia-Fernandez, Ke-Jin Zhou, Alessandro Nicolaou, Thomas Lippert, Jun Cheng, and Andrew R. Akbashev

Abstract:

Structural degradation of oxide electrodes during the electrocatalytic oxygen evolution reaction (OER) is a major challenge in water electrolysis. Although the OER is known to induce changes in the surface layer, little is known about its effect on the bulk of the electrocatalyst and its overall phase stability. Here, we show that under OER conditions, a highly active SrCoO3–x electrocatalyst develops bulk lattice instability, which results in the formation of molecular O2 dimers inside the bulk and nanoscale amorphization induced via chemo-mechanical coupling. Using high-resolution resonant inelastic X-ray scattering and first-principles calculations, we unveil the potential-dependent evolution of lattice oxygen inside the perovskite and demonstrate that O2 dimers are stable in a densely packed crystal lattice, thus challenging the assumption that O2 dimers require sufficient interatomic spacing. We also show that the energy cost of local atomic rearrangements in SrCoO3–x becomes very low under the OER conditions, leading to an unusual amorphization under intercalation-induced stress. As a result, we propose that the amorphization energy can be calculated from the first principles and can be used to assess the stability of electrocatalysts. Our study demonstrates that extreme oxidation of electrocatalysts under OER can intrinsically destabilize the lattice and result in bulk anion redox and disorder, suggesting why some oxide materials are unstable and develop a thick amorphous layer under water electrolysis conditions.

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