INTRODUCTION
Zinc oxide (ZnO) is one of most promising II−VI compound
semiconductor materials, because it has a direct band gap of
3.37 eV, a high-exciton binding energy of 60 meV, and a high
electron mobility of around 100 cm2 V−1 s−1 at room
temperature. One-dimensional (1D) ZnO nanostructures can
now be formed with favorable physical and chemical properties.
The ZnO nanostructure has a hexagonal wurtzite lattice and
exhibits favorable piezoelectricity as a result of the built-in
polarization along its c-axis. Numerous exciting ZnO nanowire
applications are currently available. They include the ultraviolet
(UV) nanolaser,1 field-effect transistor,2 solar cell,3 gas sensor,4
UV photodetector,5 light emitting diode,6 and nanogenerator.
7−11 The nanogenerator is attracting substantial attention
from researchers because ZnO exhibits highly efficient
piezoelectricity. The function of the nanogenerator is to
convert mechanical energy to electricity coupled semiconducting
and piezoelectric properties.