Abstract
High quality robust two-dimensional electron gas (2DEG) LaAlO3/SrTiO3 (LAO/STO) interfaces are produced using pulsed laser deposition and an acid-free substrate Ti-termination process, resulting in single unit cell terraces. Temperature dependent resistance measurements show two hysteresis anomalies around 80 K and 160 K. By using Hall measurements, we find an Arrhenius dependence in charge carrier density describing a partial carrier freeze-out below ∼80 K. We show that these two resistance anomalies are unrelated to the temperature dependence of the charge carrier density despite the tempting coincidence of the low temperature hysteresis feature and the freeze-out process. A two-carrier model is required to accurately estimate the activation energy of the thermally activated type charge carriers, which are found to be ∼5 to 7 meV. These results support the theory that oxygen vacancy defects contribute to the metallic conductivity at the 2DEG LAO/STO interface even for annealed samples.
Highlights
The observed properties of this interface have evolved substantially since the initial discovery
We show that these two resistance anomalies are unrelated to the temperature dependence of the charge carrier density despite the tempting coincidence of the low temperature hysteresis feature and the freeze-out process
We report that an acid-free substrate titanium termination procedure results in conductive LAO/STO interfaces
Summary
±2 T using both field sweeping for each temperature and continuous temperature sweep mode at a set field. Where m is the diffraction order, a is the lattice parameter, Q is the momentum transfer, and N is the number of unit cells contributing to the interference. A slightly reduced out of plane LAO lattice parameter of 3.76 Å was used to fit all samples. It differs from the bulk LAO parameter at 300 K by 0.03 Å. The thickness estimates from both XRD and XRR measurements agree to within ±1 Å (Table I),
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