In-plane lattice parameter determination of Zn:LiNbO3 thin films epitaxially grown on x-cut LiNbO3 substrates using X-ray diffraction methods

As a precursor material for electrooptical applications in the integrated optics, nominal pure as well as Zn‐doped stoichiometric LiNbO3 thin films of a few µm thickness were grown by liquid phase epitaxy on congruent LiNbO3 substrates. The crystalline perfection and lattice parameters of the epitaxially grown films were investigated by means of high‐resolution X‐ray diffraction methods. The symmetric θ /2θ ‐diffractograms show a lattice parameter increase perpendicular to the sample surface (Δd /d)⊥ up to 10–3 with increasing Zn content. X‐ray diffraction reciprocal space measurements taken up with asymmetric reflections are well suited to determine the in‐plane lattice parameters of the grown films. Despite different Zn contents, the Zn:LiNbO3 thin films reveal a distinctly pseudomorphous growth. Using the generalized Hooke's law in matrix way of writing and taking the measured values into account, the relaxed lattice parameters of the grown films as well as the in‐plane strain and tension components have been numerically calculated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)