Even when a film thickness is extremely thin, the crystallographic orientation relationship with the substrate can be easily analyzed using Rigaku's SmartLab multipurpose diffractometer equipped with an in-plane attachment by performing the in-plane reciprocal lattice map measurement method. In the in-plane diffraction method, X-rays enter the surface of a thin-film sample at a glazing angle—this is why the signals from a thin film can be effectively detected. By acquiring the signals while changing the orientation of the sample little by little, information related to the orientation of the thin-film sample can be obtained using the reciprocal lattice map measurement.
In the example shown in the figure above, a thin MgO buffer layer of about 7 nm thickness is found to be epitaxially grown. Analysis reveals it to have the orientational relationship shown in the figure to the right (ZnO (0001)  // MgO (111)  // Sapphire (0001) ).
Appl. Phys. Lett., (2001) vol.78, no.21, pp3352-3354, Y.F. Chen et al.