Superior Functionality by Design: Selective Ozone Sensing Realized by Rationally Constructed High-Index ZnO Surfaces

A new technique is reported for the transformation of smooth nonpolar ZnO nanowire surfaces to zigzagged high-index polar surfaces using polycrystalline ZnO thin films deposited by atomic layer deposition (ALD). The c-axis-oriented ZnO nanowires with smooth nonpolar surfaces are fabricated using vapor deposition method and subsequently coated by ALD with a ZnO particulate thin film. The synthesized ZnOZnO coreshell nanostructures are annealed at 800 degrees C to transform the smooth ZnO nanowires to zigzagged nanowires with high-index polar surfaces. Ozone sensing response is compared for all three types of fabricated nanowire morphologies, namely nanowires with smooth surfaces, ZnOZnO coreshell nanowires, and zigzagged ZnO nanowires to determine the role of crystallographic surface planes on gas response. While the smooth and coreshell nanowires are largely non-responsive to varying O-3 concentrations in the experiments, zigzagged nanowires show a significantly higher sensitivity (ppb level) owing to inherent defect-rich high-index polar surfaces.