Growth behavior of nonpolar ZnO on M-plane and R-plane sapphire by metalorganic vapor phase epitaxy

M-plane and A-plane ZnO films were grown on M-plane and R-plane sapphire substrates respectively. At high growth temperatures and/or VI/II ratios, ZnO grew along the direction perpendicular to the c-axis. On the other hand, at low growth temperatures and/or VI/II ratios, ZnO grew along the c-axis direction. A very smooth ZnO film was achieved on R-plane sapphire under a very low VI/II ratio condition. This was because the lateral growth was accelerated by a very strong tendency of growing along the c-axis. In contrast, on M-plane sapphire, C-plane ZnO nanorods tilted by 30 degrees from the normal of the surface were formed under this growth condition.