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

Abstract

Sr Ru O 3 (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 0.1to300mTorr—was investigated. SRO ablation plumes showed a shape transition from forward directed to confined isotropic at 60mTorr. Also, all measured properties of SRO films displayed significant changes at 60mTorr. Out-of-plane lattice constants and strains of SRO films were quite large for low-pressure growth (up to 10mTorr), but became notably minimized at 60mTorr 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 10mTorr, followed by the step flow growth mode at 60mTorr and step flow plus two-dimensional growth at 200mTorr, reverting then back into island growth at 300mTorr. Only those SRO films exhibiting the step flow growth mode showed a high TC. The correlation between oxygen pressure and film properties is discussed in terms of strain and compositional effects.