Effects of Bottom Electrode on the Structural and Electrical Characteristics of Barium Titanate Thin Films

Barium titanate thin films of 50 nm thickness and having a composition of Ba(Zr0.12Ti0.88)O3 (BZT) were deposited on different electrodes of LaNiO3 (LNO), Pt and RuO2 by rf magnetron sputtering at 400°C. Highly crystallized and (100)-oriented BZT films were formed by deposition on the (100)-textured LNO electrode, but poorly crystallized films were obtained by deposition on the other two electrodes. The films deposited on LNO were smooth and had a flat interface that epitaxially bonded with the LNO electrode. However, the films deposited on Pt or RuO2 were rough and had a rugged film/electrode interface. High interdiffusion was found at the BZT/RuO2 interface, but not at the other two interfaces. The dielectric constant of the film on LNO was ∼250, but that of the films on Pt or RuO2 was ∼120. For the former, a high and stable insulating characteristic against biasing voltage was also found, i.e., a low leakage current of 10-9 A/cm2 was maintained before reaching a high onset voltage of 5 V. In contrast, the leakage current rapidly increased to >10-7 A/cm2 with increasing bias to 5 V or 2 V for the films deposited on Pt or RuO2, respectively. The relationship of current versus time (J–t) measured at 380 K also revealed the superior insulating property of the film deposited on LNO compared to the other two films.