Structural Analysis of ZnO Nanorods Grownon a ZnO Homo-Buffer Layer by Using MOCVD

摘要

Vertically well-aligned ZnO nanorods were fabricated on Al_2O_3with ZnO homo-buffer layersor GaN interlayers by using a catalyst-free metal-organic chemical vapor deposition (MOCVD).X-ray diffraction (XRD) measurements demonstrated that, compared with the nanorods grownon the GaN interlayer, a substantial amount of structural disorders existed in the ZnO nanorodsgrown on the ZnO homo-buffer layer. Field-emission transmission electron microscope (FE-TEM)measurements from the interfaces of the nanorods and the substrates also exhibited structuraldisorders existing in the bottom part of the ZnO nanorods grown on the sapphire and on theZnO homo-buffer layer while no distinguishable disorder was observed at the ZnO/GaN interface.However, extended X-ray absorption fine structure measurements at the Zn K edge revealed that asmall, but distinguishable, amount of structural disorder existed in the Zn-O pairs in the beginningof the nanorod growth. Our observation strongly suggests that structural strain due to the surfaceroughness of the ZnO homo-buffer layer and to the lattice mismatch between the ZnO and the GaNmainly contributed to island growth in the beginning of the ZnO nanorod growth.