Thermodynamic Ground States of Complex Oxide Heterointerfaces

F. Gunkel, S. Hoffmann-Eifert, R. A. Heinen, Dennis Valbjørn Christensen, Yunzhong Chen, Nini Pryds, R. Waser, R. Dittmann

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The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature equilibrium conductivity measurements. We unambiguously identify two distinct classes of oxide heterostructures: For epitaxial perovskite/perovskite heterointerfaces (LaAlO3/SrTiO3, NdGaO3/SrTiO3, and (La,Sr)(Al,Ta)O3/SrTiO3), we find the 2DEG formation being based on charge transfer into the interface, stabilized by the electric field in the space charge region. In contrast, for amorphous LaAlO3/SrTiO3 and epitaxial γ-Al2O3/SrTiO3 heterostructures, the 2DEG formation mainly relies on the formation and accumulation of oxygen vacancies. This class of 2DEG structures exhibits an unstable interface reconstruction associated with a quenched nonequilibrium state.
Original languageEnglish
JournalA C S Applied Materials and Interfaces
Issue number1
Pages (from-to)1086–1092
Number of pages7
Publication statusPublished - 2017


  • 2DEG
  • Defect-chemistry
  • Interface chemistry
  • Oxide heterointerfaces
  • Thermodynamics


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