Orientation of vanadyl phthalocyanine grown by molecular beam epitaxy on KBr-KCl mixed crystals with various lattice constants

We have studied the effect of the lattice constants of substrates on the crystal orientation of films grown by molecular beam epitaxy. Vanadyl phthalocyanine films were epitaxially grown on KBr-KCl mixed crystals with continuously varying lattice constants. The unidirectional (3×3) R 45° orientation and the bidirectional (√10×√10) R ±27° orientation were predominant on the KBr-rich and KCl-rich substrates, respectively. We found that the orientation changes from the (3×3) R 45° structure to the (√10×√10) R ±27° structure at about the KCl fractions of 20 wt%.