Table 1.
Electronic reconstruction across the polar interfaces of ferroelectric heterostructures
| Structure | Electrode termination | Valence mismatch | Polarization state | Internal field (V) | Electrostatic potential step (V) |
| BFO/LSMO | A site | −0.3 | Down | −0.55 ± 0.22 | 1.2 ± 0.3 |
| B site | +0.3 | Up | 0.66 ± 0.21 | ||
| BFO/SRO | A site | −1.0 | Down | −0.75 ± 0.18 | 1.5 ± 0.3 |
| B site | +1.0 | Up | 0.79 ± 0.20 | ||
| BFO/Nb:STO | A site | −1.0 | Down | −1.2 ± 0.3 | 2.6 ± 0.4 |
| B site | +1.0 | Up | 1.4 ± 0.3 | ||
| PZT/LSMO | A site | +0.7 | Up | 0.86 ± 0.32 | 1.6 ± 0.4 |
| B site | −0.7 | Down | −0.72 ± 0.25 |
The valence mismatch at the interface is calculated by assuming the ionic charge assignment with the nominal bulk valence for each layer. For example, the MnO2-terminated (La0.7Sr0.3O-MnO2-BiO-FeO2) interface has the sheet charge density as +0.7e/-0.7e/+1e/-1e; thus the valence mismatch is calculated to be -0.7 + 1 = 0.3. The interface electrostatic potential step is calculated to be the difference between the biased-voltages of the two possible interface configurations within the same structure. The data on LSMO/BFO heterostructures were obtained from the piezoresponse measurements with Au as top electrodes; all the other heterostructures were measured with PFM tips as top contacts. The B site-terminated SRO is achieved by depositing an atomic layer of TiO2 on top of SrO-terminated SRO.