Investigation of dead-layer thickness in SrRuO3/Ba0.5Sr0.5TiO3/Au thin-film capacitors

Thin-film capacitors, with barium strontium titanate (BST) dielectric layer s between 7.5 and 950 nm in thickness, were fabricated by pulsed-laser depo sition. Both crystallography and cation chemistry were consistent with succ essful growth of the BST perovskite. At room temperature, all capacitors di splayed frequency dispersion such that epsilon (100 kHz)/epsilon (100 Hz) w as greater than 0.75. The dielectric constant as a function of thickness wa s fitted, using the series capacitor model, for BST thicknesses greater tha n 70 nm. This yielded a large interfacial d(i)/epsilon (i) ratio of 0.40 +/ -0.05 nm, implying a highly visible parasitic dead layer within the capacit or structure. Modeled consideration of the dielectric behavior for BST film s, whose total thickness was below that of the dead layer, predicted anomal ies in the plots of d/epsilon against d at the dead-layer thickness. In the capacitors studied here, no anomaly was observed. Hence, either (i) 7.5 nm is an upper limit for the total dead-layer thickness in the SRO/BST/Au sys tem, or (ii) dielectric collapse is not associated with a distinct interfac ial dead layer, and is instead due to a through-film effect. (C) 2001 Ameri can Institute of Physics.