Structure-Property Relationships in W Doped (Ba,Sr)TiO3 Thin Films Deposited by Pulsed Laser Deposition on (001) MgO

Abstract

AbstractBaxSr(1-x)TiO3 films (BST) with x=0.5, 0.6, 0.7, containing 1% W, were grown by pulsed laser deposition on MgO (001) substrates in an oxygen pressure from 3 to 500 mTorr, at a substrate temperature of 720 C. The crystal structure of the film, as determined from x-ray diffraction, was fit to a tetragonal distortion of a cubic lattice having two in-plane lattice parameters. The in and out-of-plane lattice parameters c, a, á, and lattice distortion (a/c and á/c) were calculated from the positions of the measured BST reflections ((004), (024) and (224)). The dielectric properties of the film at 2 GHz were measured using gap capacitors deposited on top of the dielectric film, at room temperature. For all compositions, as a function of the oxygen deposition pressure, a peak in the change in the dielectric constant, as a function of an applied electric field (0 – 80 kV/cm), was observed for films deposited in 50 mTorr of oxygen. Unlike the pure BST, the dielectric Q was insensitive to the oxygen deposition pressure. The largest Kfactor (K=(ε(0)-ε(V)/ε(0) x Q(0)) for films deposited from Ba0.6Sr0.4TiO3 target were observed in a film that had a minimum in-plane strain, where a~á.