In-plane orientation relationship between two c-axis oriented films

gasidit

We fabraicated Au/BTO/STO/p-Si(001) MFIS structure. The BTO and the STO films were highly c-axis orientation as investigated by XRD (2q-w) and pole figure analysis. This indicates that lattice planes of both films are well aligned and random in a out-of-plane and an in-plane direction, respectively.

However, I am wondering about the relationship of lattice planes in a in-plane direction of the STO and BTO films.
Is there specific epitaxial relatationship between these two films?