Ferroelectric stripe domains in PbTiO3 thin films: Depolarization field and domain randomness

Abstract

Observation of stripe domains in PbTiO3 thin films using standard x-ray diffraction analysis at room temperature is discussed. High-quality c-axis oriented thin films of varying thickness, from 6 to 210 unit cells, were grown on buffered NH4–HF etched SrTiO3(001) and Nb:SrTiO3(001) substrates using off-axis radio frequency magnetron sputtering. High-resolution linear Qx scans reveal a superstructure around the specular Bragg peaks, consistent with the presence of ferroelectric stripe domains. For thin samples, the stripe width is found to be proportional to the square root of the film thickness, with random in-plane orientation of domains. For films with a thickness of more than ∼100 unit cells, both monodomain samples and stripe domains were observed. We present evidence for the presence of a threshold depolarization field, above which there is a monotonically decreasing relationship between the domain width and the depolarization field. Furthermore, simulations show that random variations in size of the domains affect the separation of the diffuse scattering peaks from that of the specular reflection.