Two-Dimensional Electron Gas with High Mobility Forming at BaO/SrTiO₃ Interface

【摘要】 Two-dimensional electron gas （2DEG） with high electron mobility is highly desired to study the emergent properties and to enhance future device performance.Here we report the formation of 2DEG with high mobility at the interface between rock-salt Ba O and perovskite Sr Ti O₃.The interface consists of the ionically compensated Ba O_1-δlayer and the electronically compensated Ti O₂ layer,which is demonstrated as a perfect interface without lattice mismatch.The so-formed interface features metallic conductivity with ultralow square resistance of7.3×10^-4Ω/□at 2 K and high residual resistance ratios R_{300 K}/R_{2 K} up to 4200.The electron mobility reaches69000 cm²·V^-1·s^-1at 2 K,leading to Shubnikov–de Haas oscillations of resistance.Density functional theory calculations reveal that the effective charge transfers from Ba O to the Ti 3d_xy orbital occur at the interface,leading to the conducting Ti O₂ layer.Our work unravels that Ba O can adapt itself by removing oxygen to minimize the lattice mismatch and to provide substantial carriers to Sr Ti O₃,which is the key to forming 2DEGs with high mobility at the interfaces.更多还原

【Abstract】 Two-dimensional electron gas （2DEG） with high electron mobility is highly desired to study the emergent properties and to enhance future device performance.Here we report the formation of 2DEG with high mobility at the interface between rock-salt Ba O and perovskite Sr Ti O₃.The interface consists of the ionically compensated Ba O_1-δlayer and the electronically compensated Ti O₂ layer,which is demonstrated as a perfect interface without lattice mismatch.The so-formed interface features metallic conductivity with ultralow square resistance of7.3×10^-4Ω/□at 2 K and high residual resistance ratios R_{300 K}/R_{2 K} up to 4200.The electron mobility reaches69000 cm²·V^-1·s^-1at 2 K,leading to Shubnikov–de Haas oscillations of resistance.Density functional theory calculations reveal that the effective charge transfers from Ba O to the Ti 3d_xy orbital occur at the interface,leading to the conducting Ti O₂ layer.Our work unravels that Ba O can adapt itself by removing oxygen to minimize the lattice mismatch and to provide substantial carriers to Sr Ti O₃,which is the key to forming 2DEGs with high mobility at the interfaces.更多还原