Size dependence of dielectric constant in a single pencil-like ZnO nanowire.

Scanning conductance microscopy (SCM) is used to measure the dielectric constant of a single pencil-like zinc oxide (ZnO) nanowire with the diameters ranging from 85 to 285 nm. As the diameter decreases, the dielectric constant of ZnO nanowire is found to decrease from 6.4 to 2.7, which is much smaller than that of the bulk ZnO of 8.66. A core-shell composite nanowire model in terms of the surface dielectric weakening effect is proposed to explore the origin of the size dependence of dielectric constant, and the experimental results are well explained.