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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: TEM-based Nanoanalysis and Microstructure of thin films (joint session KFM/CPP)

KFM 14.5: Vortrag

Donnerstag, 19. März 2020, 15:40–16:00, HSZ 301

Uncloaking structural information of ultra-thin oxide films by surface enhanced Raman spectroscopy — •Mads C. Weber¹, Sebastian Heeg², Roman Wyss³, Martin Sarott¹, Morgan Trassin¹, and Manfred Fiebig¹ — ¹Department of Materials, ETH Zurich — ²Department of Information Technology and Electrical Engineering, ETH Zurich — ³Department of Mechanical and Process Engineering, ETH Zurich

Strained oxide thin films are a source for properties nonexistent in bulk form such as ferrelectricity in SrTiO₃ or altered conductivity in nickelates. These physical properties result commonly from subtle structural distortions. Unfortunately, subtle distortions and specifically oxygen displacements are chronically difficult to probe hindering an in-depth understanding of the phenomena. Here, we introduce surface enhanced Raman spectroscopy (SERS) – a technique so far restricted to molecules and carbon-nanostructures – to scrutinize the structure of oxide thin films. A porous gold membrane deposited on the sample acts as antenna and amplifies the Raman signal of the outer layers only. Using this method, we set the Raman spectra of our model thin film LaNiO₃ apart from the substrate giving the important structural insight. Beside information on the strain state of LaNiO₃, we identify an ultra-thin surface layer structurally different from the rest of the film. Such a surface layer was so far only theoretically predicted, however, never observed. In general, we anticipate that the introduction of SERS to reign of complex oxides films will help to understand the link between novel physical phenomena and structural distortions.