The influence of energetic bombardment on the structure and properties of epitaxial SrRuO₃ thin films grown by pulsed laser deposition

SrRuO₃ epitaxial thin films were prepared by pulsed laser deposition (PLD) under a range of growth conditions to study the impact of bombardment on properties. Growth conditions favoring energetic bombardment resulted in SrRuO₃ films with expanded in-plane and out-of-plane lattice constants. In particular, SrRuO₃ films with pseudocubic out-of-plane lattice constants as large as 4.08 Å were deposited (3.8% larger than the bulk value). Those films with expanded lattices had greater resistivities and depressed Curie transition temperatures. The relative lattice mismatch between film and substrate was found to temper the effect of bombardment such that as the mismatch increased, a higher degree of bombardment was required to produce extended lattice parameters. The pressure-dependent energetic species inherent to PLD and their interaction with the ambient are believed to be the source of the bombarding flux. Further experiments confirmed that in the range of 20-200 mTorr, oxygen/ozone partial pressure had a negligible effect on the film properties.