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O: Fachverband Oberflächenphysik
O 95: Thin Oxides and Oxide Layers I (joint session DS/HL/O)
O 95.2: Vortrag
Donnerstag, 19. März 2020, 09:45–10:00, CHE 91
Nano-scale spectroscopic analysis of LaAlO3/SrTiO3 interfaces using scattering-type Scanning Near-field Optical Microscopy — •Yigong Luan1, Julian Barnett1, Marc Rose2, Felix Gunkel2, Martin Lewin1, and Thomas Taubner1 — 1Institute of Physics (IA) RWTH Aachen — 2PGI-3, Forschungszentrum Jülich
In the group of functional oxide materials, the interface of bulk insulators LaAlO3 and SrTiO3 (LAO/STO) attracts attention due to its highly confined and conductive two-dimensional electron gas (2DEGs), which could be interesting for high-electron-mobility transistors. 2DEGs at oxide interfaces result from electronic reconstruction, which is highly dependent on the local structure [1]. The extraction of their electronic properties is difficult for far-field spectroscopy and conventional nano-resolved microscopy (e.g. STM), as the conducting layer is highly confined and buried below an insulating layer (LAO). We overcome these limitations by using scattering-type Scanning Near-field Optical Microscopy for a quantitative extraction of electron properties from "phonon-enhanced spectroscopy", as the presence of free charge carriers leads to significant changes to the phonon resonance due to plasmon-phonon coupling [2]. We use an improved model (Finite Dipole Model) combining with Transfer Matrix Method to interpret the experimental results, investigating the influence of both LAO layer and 2DEGs on the STO phonon near-field resonance in detail, which allows us to extract the local electronic properties.
[1] A. Ohtomo et al., Nature 427, 423 (2004)
[2] M. Lewin et al., Adv. Funct. Mater, 28. 1802834 (2018)