Growth and structural characterization study of ZnO nanorods and multidimensional nanostructures

Abstract

Nanoscale one-dimensional (1D) semiconductor materials, i.e., nanowires and nanorods, exhibiting photonic and electronic confinement in two dimensions have been the subject of considerable attention in recent years due to its potential application in nanoscale electronic and optoelectronic devices. Particularly, since ZnO has a wide direct band-gap of 3.37 eV at room temperature and a much larger free exciton binding energy (60 meV) than that of GaN (25 meV) the thermal energy at room temperature (26 meV) [1,2], it has been recognized as a candidate for efficient blue or ultraviolet light emitting devices at room temperature under low excitation energy. For these practical applications, high-density and well-ordered ZnO nanostructures will be needed. Among the various techniques for the growth of ZnO nanorods, MOCVD has been demonstrated to be a promising tool for the synthesis of ZnO nanorods with uniform length and thickness due to the feasibility of large area growth of well-aligned ZnO nanorods without metal catalyst. However, in spite of the enormous potential of MOCVD for the growth of the ZnO nanorods, little is known about effects of growth parameter on ZnO nanorods growth process. Insight into the fundamental mechanisms controlling the MOCVD growth of ZnO nanorods can be obtained by studying the effect of external parameters such as substrate temperature, reactor pressure and VI/II ratios on growth rate and morphology. In order to understand the atomic features of ZnO products governed by these growth parameters, growth and structural properties of ZnO nanorods have been investigated. In addition, to realize light emission from the nanorods through electron injection, they should be electrically connected to the metal layer. Herein, an alternative method of forming the metal contact layer was also presented to use the well aligned ZnO nanorod arrays as an active layer. The evolution of ZnO nanorods by metalorganic chemical vapor deposition on sa...