Fig. 5: Modulation of 2DEG density by field-induced ionic polarization and associated charges in LaAlO3.
a Profiles of the displacement of B-site cation (δB) measured across the LaAlO3/SrTiO3 heterostructure under applied voltages. b Profiles of the polarization (Pi) across the LaAlO3/SrTiO3 heterostructure under applied voltages. The out-of-plane component of polarization along the field direction was plotted. The polarization arises only in the LaAlO3 and is switchable by the electric field. c Charge density modulating from the unbiased state plotted as a function of applied voltage. The values obtained by different methods are included; inline electron holography data (black dot) representing the net charge modulation, Ti3+ fraction determined from EELS Ti-L2,3 edge representing 2DEG modulation, the calculated dielectric charges (ε0εrEa, blue bar), and the dielectric charges (ε0εrEa) together with the measured polarization charges (Pi, red bar). The dielectric constant (εr) of 20 and 300 was used for LaAlO3 and SrTiO3, respectively. The modulation of net charge density is accounted for well by considering both dielectric charges (ε0εrEa) and polarization charge (Pi) of LaAlO3.
