Optoelectronic properties in vertically aligned ZnO/Si-nanopillars

An effective method of fabricating vertically aligned silicon nanopillars (Si-NPs) was realized by using the self-assembled silver nanodots as natural metal-nanomask for subsequent etching process. Ultrathin (~9 nm) ZnO films were deposited on the Si-NPs by atomic layer deposition to enhance the field emission property. The turn-on field defined by the 10 μA/cm² current density criterion is ~ 0.74 V/μm with an estimated β ~ 1.33×10⁴. The low turn-on field and marked enhancement in β were attributed to the small radius of curvature, high aspect ratio, and perhaps more importantly, proper density distribution of the ZnO/Si-NPs. On the other hand, room-temperature ultraviolet (UV) luminescence was investigated for the atomic layer deposited ZnO films grown on Si nanowires fabricated by self-masking dry etching in hydrogen-containing plasma. For films deposited at 200°C, an intensive UV emission corresponding to free-exciton recombination was observed with a nearly complete suppression of the defect-associated broad visible range emission peak.