Polarization-dependent soft-x-ray absorption of highly oriented ZnO microrod arrays

Polarization-dependent x-ray absorption measurements were performed on crystalline ZnO three-dimensional arrays consisting of highly oriented microrods as well as on particulate thin films consisting of monodisperse spherical nanoparticles. Strong anisotropic effects have been observed for the highly oriented ZnO rods, but not for the isotropic spherical nanoparticles. Full-potential calculations of the orbital-resolved x-ray absorption of a ZnO wurtzite periodic crystal, including Zn 3d among the valence states, show very good agreement with the experimental findings. Comprehensive fundamental knowledge of the electronic structure of ZnO is obtained by probing and demonstrating the orbital symmetry of oxygen and its contribution to the conduction band of this important II-VI semiconductor.