Low-Temperature Sputtering and Polarity Determination of Vertically Aligned ZnO Nanocolumns

TL;DR

This paper demonstrates a low-temperature, scalable sputtering method to grow vertically aligned ZnO nanocolumns on silicon, controlling morphology and polarity through sputtering conditions and substrate preheating, with implications for flexible electronics.

Contribution

It introduces a low-temperature sputtering process for ZnO nanocolumns that controls polarity and morphology via sputtering parameters and substrate preheating, suitable for flexible electronics.

Findings

Higher sputtering pressure induces isolated nanocolumns due to shadowing.

Preheating modifies SiOx, influencing ZnO polarity and structure.

O-polar ZnO exhibits higher piezoelectric response and lower dielectric loss.

Abstract

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.