Nucleation of strontium titanate films grown by PLD on silicon: a kinetic model

Abstract

Nucleation and growth of strontium titanate (SrTiO 3) films, prepared by pulsed laser ablation deposition, has been investigated during on a (100) silicon substrate surface, using atomic force microscopy. A nucleation kinetic model has been derived from an analysis of the particle size distribution. The reconstructed nucleation trend was characterised by a systematic behaviour: the nucleation rate, negligible at the beginning, reaching a maximum after a certain time and tending to zero for longer deposition time. This behaviour prompted the design of a simple model which correlates these phenomena to two specific aspects: i) the nucleation occurs at certain limited number of sites on the substrate surface; ii) the nucleation process shows a temperature-dependent incubation time. In this model, the incubation time is related to the formation time of a ‘critical SrTiO 3 cluster’. The size of the critical cluster is determined both by thermodynamic quantities and by the amount of interface misfit strain energy of SrTiO 3 lattice with respect to substrate.