Transition Between ZnO Nanorods and ZnO Nanotubes with Their Antithetical Properties

Abstract

In this study, we present the fabrication and transition between ZnO nanorods (ZNRs) and ZnO nanotubes (ZNTs) with their antithetical properties. We etch the aqueous chemically grown ZNRs into ZNTs via a chemical etching method in KCl solution without any surface and subsurface processing on ZNRs. In order to have a perfect transition, we change the parameters, such as KCl molar concentration, etching time, and catalyzing temperature. The SEM images show a perfect transition from ZNRs into ZNTs with almost the same diameter of around 60 nm, which is one of the smallest achieved for a transition at this time. The transition dependence of ZNRs into ZNTs on the diameter and the surface roughness of ZNRs is also substantiated by applying the etching on ZnO nanopyramids that are either not etched at the given etching time or started etching with the dissolution of lateral walls. The two different structures are characterized via a two-probe method to look at the antithetical electrical behavior of ZNRs and ZNTs. It is proved that ZNTs are more sensitive, have higher levels of current, and have lower turn-on voltages because ZNTs have a higher level of surface and subsurface oxygen vacancies with a higher surface-to-volume ratio as compared to ZNRs.