Quantifying mean inner potential of ZnO nanowires by off-axis electron holography.

Off-axis electron holography has been used to quantitatively determine the mean inner potential of ZnO. [0001] grown ZnO nanowires with hexagonal cross-sections were chosen as our samples because the angle between the adjacent surfaces is 120°, as confirmed by electron tomography, so the entire geometry of the nanowire could be precisely determined. The acceleration voltage of the transmission electron microscope was accurately calibrated by convergent beam electron diffraction (CBED)-higher-order Laue-zone (HOLZ) analyses. ZnO nanowires were tilted away from zone-axis to avoid strong dynamical diffraction effect, and the tilting angles were determined by CBED patterns. Our experimental data found a mean inner potential of ZnO as 14.30±0.28 V.