Interfacial structure and defect analysis of nonpolar ZnO films grown on R-plane sapphire by molecular beam epitaxy

The interfacial relationship and the microstructure of nonpolar (11-20) ZnO films epitaxially grown on (1-102) R-plane sapphire by molecular beam epitaxy are investigated by transmission electron microscopy. The already-reported epitaxial relationships [1-100](ZnO)parallel to[11-20](sapphire) and < 0001 >(ZnO)parallel to[-1101](sapphire) are confirmed, and we have determined the orientation of the Zn-O (cation-anion) bond along [0001](ZnO) in the films as being uniquely defined with respect to a reference surface Al-O bond on the sapphire substrate. The microstructure of the films is dominated by the presence of I-1 basal stacking faults [density=(1-2)x10(5) cm(-1)] and related partial dislocations [density=(4-7)x10(10) cm(-2)]. It is shown that I-1 basal stacking faults correspond to dissociated perfect dislocations, either c or a+c type. (c) 2008 American Institute of Physics.