Controlled Cobalt Oxide from Two-Dimensional Films to One-Dimensional Nanorods and Zero-Dimensional Nanoparticles: Morphology-Dependent Optical Carbon Monoxide Gas-Sensing Properties

A combined process of oblique angle deposition and pulsed laser deposition was developed to fabricate cobalt oxide with controlled nanostructures. By the manipulation of the tilt angles of substrates and the oxygen pressures in a reaction chamber, the fabricated cobalt oxide exhibited a structural evolution from two-dimensional (2D) compact and columnar films to one-dimensional (1D) nanorods, composites of nanorods and nanoparticles, and zero-dimensional (0D) nanoparticles. The growth mechanism was examined in detail. The fabricated cobalt oxide nanostructures demonstrated an improved optical carbon monoxide (CO) gas-sensing performance, including sensitivity, response and recovery time, and stability with the decreased dimension, owing to the high surface-to-volume ratio, pore structure, and small particle size.