Formation of ZnO Nanocones Using Wet Chemical Etching of ZnO Nanorods in an Aqueous Solution of HCl

In this report, a simple wet chemical etching of ZnO nanorods to fabricate large area ZnO nanocones is demonstrated. The cone-like morphology formation utilizes anisotropic etching rate on the different crystal planes of ZnO nanorods in an aqueous solution of HCl (HCl [aq]). To form ZnO nanocones, single crystalline ZnO nanorods with a flat hexagonal shape are synthesized on p-Si(100) using hydrothermal method at 90 °C and then, are immersed in HCl [aq]. Electron microscopy reveals that the HCl [aq] treatment of ZnO nanorods significantly etched sidewalls of nanorods, resulting in the cone-like morphology formation. The nanocone formation is the most noticeable when the etching occurred in HCl [aq] with a pH of 2.5–3.0 for 5 min etching time. Geometrical analysis using the electron microscopy reveals that the sidewall of a ZnO nanocone have formed a plane indexed as (0-111) after the etching process.