Correlation between the Dielectric Response and Thickness of Vanadium Pentoxide Nanowires

We investigated the correlation between the dielectric response and thickness of vanadium pentoxide nanowires (V2O5 NWs) by local mapping of the second harmonic (2ω) signal from electrical force microscopy (EFM). The 2ω signals measured in the EFM device are related to the dielectric response or electrical conductivity owing to mobile carrier motion determined by the charge carrier density and mobility of V2O5 NWs with different thicknesses. We constructed a two-dimensional (2D) cross-correlation distribution of the 2ω signal and the thickness of V2O5 NWs and found that they are strongly correlated, i.e., thicker NWs have a higher dielectric response. We also observed a reduced correlation between the 2ω signal and thickness under large negative tip gate voltages to modulate the charge carriers of NWs. This is attributed to the charge depletion for both thin and thick V2O5 NWs. In addition, we found that 2ω signals increase with the gate voltage, presenting the n-type behavior of V2O5 NWs with different thicknesses. Our work can improve the performance of electronic devices based on controllable dielectric properties of V2O5 NWs.