Surface roughness and strain effects on ZnO nanorod growth

Vertically aligned ZnO nanorods were fabricated on Al₂O ₃(001) substrates with various GaN interlayers by a catalyst-free metal-organic chemical vapor deposition. We observed that the shape and quality of ZnO nanorods grown on the GaN interlayers were considerably sensitive to the surface roughness of the interlayers. We also investigated orientation-dependent residual strain in the ZnO nanorods grown on Al₂O₃ substrates using polarized x-ray absorption fine structure (XAFS) measurements at Zu K edge. The XAFS revealed that the residual strain relaxation of Zn-O pairs in ab plane played a key role in the ZnO nanorod growth.