Theoretical analysis of growth of ZnO nanorods on the amorphous surfaces

Abstract

Semiconductor nanorod arrays on a substrate have a preferential alignment orientation that minimizes the excessive free energy of the system. In the case of wet chemically synthesized zinc oxide (ZnO) nanorod on the amorphous surfaces, the thermodynamic driving force determines the orientation to be normal to the surface. Among the various kinds of amorphous surfaces, the spherical seed layer composed of ZnO precursors gives isotropic radially aligned arrays. For other surfaces, such as wrinkled and planar ZnO precursor thin film, nanorod arrays are aligned to be perpendicular to the tangential line of the surface. The maximum value of the aspect ratio of the nanorod is determined by the thermodynamic relationship. The number density of nanorods per unit precursor particles decreases with increasing contact angle of the seed particles.