Thickness dependence of strain and in-plane dielectric properties of highly (001) oriented (Ba,Sr)TiO3 thin films

Highly (001) oriented (Ba,Sr)TiO3 thin films, grown on (001) LaAlO3 substrates by pulsed laser deposition, exhibit strong variation of strain over the thickness range of 20–800 nm. The tensile elastic residual strain reaches a minimum value at a thickness of 250 nm, while the inhomogeneous strain decreases gradually with increasing film thickness. The 250-nm-thick film has the largest in-plane dielectric constant due to a smallest tensile elastic strain in the film and the largest in-plane tunability of 40% is achieved in the thickest film.