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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)