Contribution of oxygen partial pressures investigated over a wide range to SrRuO₃ thin-film properties in laser deposition processing

SrRuO₃ (SRO) thin films were grown on SrTiO₃ (100) substrates using the pulsed laser deposition method. In order to fully exploit the correlation between their properties and the partial (working) pressures of oxygen in which they are grown, a wide range of pressures—from 0.1 to 300 mTorr—was investigated. SRO ablation plumes showed a shape transition from forward directed to confined isotropic at 60 mTorr. Also, all measured properties of SRO films displayed significant changes at 60 mTorr. Out-of-plane lattice constants and strains of SRO films were quite large for low-pressure growth (up to 10 mTorr), but became notably minimized at 60 mTorr and continued to change gradually with further pressure increases. Ru deficiencies seemed to occur regardless of working pressure value. The island growth mode was dominant for low pressures up to 10 mTorr, followed by the step flow growth mode at 60 mTorr and step flow plus two-dimensional growth at 200 mTorr, reverting then back into island growth at 300 mTorr. Only those SRO films exhibiting the step flow growth mode showed a high T_C. The correlation between oxygen pressure and film properties is discussed in terms of strain and compositional effects.