Epitaxial ZnO thin films were grown on (00•1) sapphire substrates by pulsed laser deposition. The structural and electrical transport properties of the films were measured as a function of the growth temperature and substrate cleaning procedure. X-ray diffraction measurements revealed that the cleaning procedure affected drastically the twin formation. Its origin could be attributed to a residual hydrocarbon layer or defects (OH- or O vacancies) at the sapphire surface. The electrical transport characteristics of the films were found to depend moderately on the existence of twinning.

How to Prevent Twin Formation in Epitaxial ZnO Thin Films Grown on C-Plane Sapphire. Steplecaru, C.S., Martín-González, M.S., Fernández, J.F., Costa-Krämer, J.L.: Thin Solid Films, 2010, 518[16], 4630-3