Title: Revealing the Interaction of Charge Carrier–Phonon Coupling by Quantification of Electronic Properties at the SrTiO3/TiO2 Heterointerface

Authors: Ting-Xiao Qin*, En-Ming You, Jia-Ye Zhang, Hai-Long Wang, Kelvin H. L. Zhang*, Bing-Wei Mao, and Zhong-Qun Tian

Abstract: Oxide heterointerfaces with high carrier density can interact strongly with the lattice phonons, generating considerable plasmon–phonon coupling and thereby perturbing the fascinating optical and electronic properties, such as two-dimensional electron gas, ferromagnetism, and superconductivity. Here we use infrared-spectroscopic nanoimaging based on scattering-type scanning near-field optical microscopy (s-SNOM) to quantify the interaction of electron–phonon coupling and the spatial distribution of local charge carriers at the SrTiO₃/TiO₂ interface. We found an increased high-frequency dielectric constant (ε_∞ = 7.1–9.0) and charge carrier density (n = 6.5 × 10¹⁹ to 1.5 × 10²⁰ cm^–3) near the heterointerface. Moreover, quantitative information between the charge carrier density and extension thickness across the heterointerface has been extracted by monochromatic near-field imaging. A direct evaluation of the relationship between the thickness and the interaction of charge carrier–phonon coupling of the heterointerface would provide valuable information for the development of oxide-based electronic devices.

Full-Link: https://pubs.acs.org/doi/10.1021/acs.nanolett.1c04698