Effective thickness and dielectric constant of interfacial layers of Pt/Bi_3.15Nd_0.85Ti₃O₁₂/SrRuO ₃ capacitors

Epitaxial c -axis-oriented Bi3.15 Nd0.85 Ti3 O12 (BNT) thin films with thickness ranging from 150 to 350 nm were deposited on conductive SrRu O3 (SRO) on (001) SrTi O3 substrates by pulsed laser deposition. The top Pt electrode was deposited by sputtering to construct a capacitor Pt/BNT/SRO. The authors have evaluated the effective thickness (ti) and dielectric constant (εi) of interfacial layers at the Pt/BNT and BNT/SRO interfaces based on the optical refractive index of the BNT layer and the capacitance frequency as well as the current-voltage characteristics of the capacitors. Using a series capacitor model, they have found that the dielectric constant of bulk BNT and the ti εi ratio are 586 and 1.46 nm, respectively. Knowing the optical dielectric constant (εopt) and the product of εopt ti of BNT thin films, the authors have estimated that the effective thickness and dielectric constant of the interfacial layers are 20.1 nm and 13.7, respectively.