A quantitative analysis on the interfacial effect in the Pt/Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3 heterostructure

The heterostructure of Pt/Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3 (Pt/BST/LSMO) with the BST thickness ranging from 120 to 550 nm was fabricated by pulsed laser deposition. The dielectric constant (e) of the heterostructure was measured under different electrical fields (E) and frequency (f). A strong thickness dependence of the value of e, the e–E dependence and the e–f dependence were observed, which can be well explained by the series-capacitor model, based on the assumption that the heterostructure electrically consists of a 'bulk' layer and an interfacial layer between the Pt and BST layers. The dielectric properties of the 'bulk' layer and the interface layer were obtained. At room temperature, the dielectric constant of the 'bulk' layer was 1204 (at 100 kHz) and had a power law dependence on frequency. The ratio of thickness over the dielectric constant (di/ei) of the interface layer, which was used to characterize the property of the Pt/BST interface, was found to be around 0.08 nm at room temperature and to be independent of frequency.