The growth rate of ZnO nanowires grown epitaxially on GaN/sapphire substrates

was studied. An inverse proportional relation between diameter and length of the

nanowires was observed, i.e., nanowires with smaller diameters grew faster than

larger ones. This unexpected result was attributed to surface diffusion of ZnO

admolecules along the sidewalls of the nanowires. In addition, the unique c-axis

growth of ZnO nanowires, which does not require a catalytic particle at the tip of

the growing nanowires was discussed by taking into account polarity, surface free

energy, and ionicity.

Surface-Diffusion Induced Growth of ZnO Nanowires. D.S.Kim, U.Gösele,

M.Zacharias: Journal of Crystal Growth, 2009, 311[11], 3216-9