Origin of ferroelectricity in carbon-doped ZnO nanocolumnars: Experimental and density-functional studies

Abstract

One-dimensional ZnO exhibits high polarization but is considered to be non-ferroelectric. Here, we show ferroelectricity in carbon-doped ZnO nanocolumnars deposited using one-step DC-unbalanced magnetron sputtering. Doping carbon effectively increases its lattice strain and turns the ZnO nanocolumnars into a ferroelectric material. The existence of a reversible permanent electric dipole is found from the P–E hysteresis loop of the carbon-doped ZnO nanocolumnars, where the highest coercivity (11.1 kV/cm) originated from zinc vacancies and remnant polarization (4.7 μ C/cm 2 ) originated from oxygen vacancies. Moreover, the presence of carbon modified the optical bandgap of the system. Supporting the experimental results, the first-principle calculation shows that the increment of C concentration decreases bandgap contributed by C 2p . Furthermore, the existence of ferroelectricity in ZnO has the potential to bring out the multiferroic properties for developing next-generation ZnO-based storage devices.