Thermodynamic Ground States of Complex Oxide Heterointerfaces

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• 作者：F. GunkelS. Hoffmann-Eifert ; R. A. Heinen ; D. V. Christensen ; Y. Z. Chen ; N. Pryds ; R. Waser ; R. Dittmann
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：January 11, 2017
• 年：2017
• 卷：9
• 期：1
• 页码：1086-1092
• 全文大小：361K
• ISSN：1944-8252

文摘

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.