A Novel p-Type ZnCo_xO_y Thin Film Grown by Atomic Layer Deposition

Reported herein is the atomic layer deposition (ALD) of novel ternary ZnCo_xO_y films possessing p-type semiconducting behavior. The preparation comprises of optimized ZnO and Co₃O₄ deposition in sub-cycles using the commercially available precursors cyclopentadienylcobalt dicarbonyl (CpCo(CO)₂), diethylzinc (DEZ) and ozone (O₃). A systematic exploration of the film's microstructure, crystallinity, optical properties and electrical properties was conducted and revealed an association with Zn/Co stoichiometry. The noteworthy results include the following: (1) by adjusting the sub-cycle of ZnO/ Co₃O₄ to 1/10, a spinel structured ZnCo_xO_y film was grown at 150 °C, with it exhibiting a smooth surface, good crystallinity and high purity; (2) the material transmittance and bandgap decreased as the Co element concentration increased; (3) the ZnCo_xO_y film is more stable than its p-type analog Co₃O₄ film; and (4) upon p-n diode fabrication, the ZnCo_xO_y film demonstrated good rectification behaviors as well as very low and stable reverse leakage in forward and reverse-biased voltages, respectively. Its application in thin film transistors and flexible or transparent semiconductor devices is highly suggested.