Strain relaxation of epitaxial (Ba0.6Sr0.4)(Zr0.3Ti0.7)O3 thin films grown on SrTiO3 substrates by pulsed laser deposition

High crystalline quality (Ba0.6Sr0.4)(Zr0.3Ti0.7)O3 (BSTZ) thin films were epitaxially grown by pulsed laser deposition on (001) SrTiO3 single crystal substrates. Their epitaxial nature was revealed by x-ray and electron diffraction. Thinnest film (∼9 nm) has largest out-of-plane lattice constant (4.135 A) and tetragonality (1.06). Films are under compressive strain. Film thicknesses above ∼9 nm were started to relax as revealed from reciprocal space mapping. Thicknesses deduced from x-ray diffraction and transmission electron microscopy methods are in good agreement. Critical thickness to relieve strain of the BSTZ film is about 7.6±0.4 nm.