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)O-3 (BZT) were deposited on different electrodes of LaNiO3 (LNO), Pt and RuO2 by rf magnetron sputtering at 400 degrees 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 similar to 250, but that of the films on PI. or RuO2 was similar to 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/cm(2) was maintained before reaching a high onset voltage of 5 V. In contrast, the leakage current rapidly increased to > 10(-7) A/cm(2) with increasing bias to 5 V or 2 V for the films deposited on Pt or RuO2, respectively. The relationship of current versus lime (J-t) measured at 380 K also revealed the superior insulating property of the film deposited on LNO compared to the other two films.