Nanospectroscopy of Infrared Phonon Resonance Enables Local Quantification of Electronic Properties in Doped SrTiO3 Ceramics

Martin Lewin, Christoph Baeumer, Felix Gunkel, Alexander Schwedt, Fabian Gaussmann, Jochen Wueppen, Paul Meuffels, Bernd Jungbluth, Joachim Mayer, Regina Dittmann, Rainer Waser, Thomas Taubner*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)

Abstract

Among the novel materials for electronic applications and novel device concepts beyond classical Si-based CMOS technology, SrTiO3 represents a prototype role model for functional oxide materials: It enables resistive switching, but can also form a 2D electron gas at its interface and thus enables tunable transistors. However, the interplay between charge carriers and defects in SrTiO3 is still under debate. Infrared spectroscopy offers the possibility to characterize structural and electronic properties of SrTiO3 in operando, but is hampered by the diffraction-limited resolution. To overcome this limitation and obtain nanoscale IR spectra of donor-doped Sr1-xLaxTiO3 ceramics, scattering-type scanning near-field optical microscopy is applied. By exploiting plasmon–phonon coupling, the local electronic properties of doped SrTiO3 are quantified from a detailed spectroscopic analysis in the spectral range of the near-field ‘phonon resonance’. Single crystal-like mobility, an increase in charge carrier density N and an increase in ε at grain boundaries (µ≈ 5.7 cm2 V−1s−1, N = 7.1 × 1019 cm−3, and ε = 7.7) and local defects (µ≈ 5.4 cm2 V−1s−1, N = 1.3 × 1020 cm−3, and ε = 8.8) are found. In future, subsurface quantification of defects and free charge carriers at interfaces and filaments in SrTiO3 can be envisioned.

Original languageEnglish
Article number1802834
JournalAdvanced functional materials
Volume28
Issue number42
DOIs
Publication statusPublished - 17 Oct 2018
Externally publishedYes

Keywords

  • ceramics
  • grain boundary
  • infrared spectroscopy
  • near-field optical microscopy
  • strontium titanate

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