Ordered misfit dislocations in epitaxial Gd doped CeO2 thin films deposited on (001)YSZ single crystal substrates

Misfit dislocations are ubiquitous in thin film systems, and their presence can profoundly affect the chemical and physical properties of materials. In the present paper, we investigate the misfit dislocation array present at the interface of a Gd doped CeO2 thin film epitaxially grown on a (001) yttria stabilized zirconia (YSZ) single crystal substrate. Because of the large misfit strain (-4.9%), the growth takes place by domain-matching epitaxy with the formation of geometrical misfit dislocations. Transmission electron microscopy (TEM) observations, combined with geometrical phase analysis and strain field calculations (in the case of elastic isotropy), reveal that the misfit dislocations are of purely edge type with Burgers vector b = ½[110] and with the dislocations lines parallel to the [1-10] direction. X-ray diffraction, combined with Monte Carlo simulations, allow to quantify the statistical properties of the dislocations ensemble. It is found that the dislocations are distributed according to a Gamma distribution with a mean dislocation spacing of 7.4 nm and with a spacing ranging from 3.5 to 12 nm, in excellent agreement with TEM observations and with the values expected from the relaxation of the misfit strain.