Microstructural characteristics of conductive SrRuO₃ thin films formed by pulsed-laser deposition

Transmission electron microscopy and high-resolution electron microscopy have been used to study microstructural properties of conductive SrRuO₃ films grown by pulsed laser deposition on (001) LaAlO₃ and (001) SrTiO₃ substrates. It was found that the SrRuO₃ films deposited on both substrates consist of mixed domains of [001] and [110] orientations, with orientation relationships that can be described as (i) (001)_f ∥ (001)_s and [110]_f ∥ [100]_s and (ii) (110)_f ∥ (001)_s and [001]_f ∥ [100]_s, respectively. The SrRuO₃ films deposited on SrTiO₃, in particular, were found to have a layered domain structure, with the [110] domain grown initially on the substate, followed by growth of the [001] oriented domain with increasing thickness. The films on SrTiO₃ are strained and have a coherent interface with the substrate. The SrRuO₃ films deposited on LaAlO₃, on the other hand, contain a high density of structural defects such as stacking faults and microtwins on the (022) planes. Microtwins as large as 50 nm in thickness are observed in the films deposited on LaAlO₃. Possible causes for the observed structural defects in the films are discussed.