Low-Temperature Sputtering and Polarity Determination of Vertically Aligned ZnO Nanocolumns
We report the low temperature growth of vertically aligned ZnO nanocolumns on Si substrates by using reactive radio frequency magnetron sputtering.High sputtering pressure combined with low substrate temperatures induce a pronounced self shadowing effect,leading to the formation of isolated nanocolumns. In contrast, lower sputtering pressure promotes void filling in deposited films, favouring the growth of dense, low roughness columnar films. Modification of native SiOx on Si surfaces via substrate preheating prior to deposition, alters the initial nucleation stage, thereby determining dominant polarity and morphology of ZnO nanostructures. O polar columnar films and nanocolumns exhibit higher effective piezoelectric coefficient, corresponding to their higher differential resistance and reduced dielectric loss, suggesting suppressed carrier induced screening of piezoelectric charges. This low thermal budget, scalable sputtering approach provides an alternative route for integrating ZnO nanostructures onto thermal constrained substrates, including those used in flexible and wearable electronics.