Tuning carrier density and phase transitions in oxide semiconductors using focused ion beams

Abstract We demonstrate spatial modification of the optical properties of thin‐film metal oxides, zinc oxide (ZnO) and vanadium dioxide (VO 2 ) as representatives, using a commercial focused ion beam (FIB) system. Using a Ga + FIB and thermal annealing, we demonstrated variable doping of a wide‐bandgap semiconductor, ZnO, achieving carrier concentrations from 10 18 cm −3 to 10 20 cm −3 . Using the same FIB without subsequent thermal annealing, we defect‐engineered a correlated semiconductor, VO 2 , locally modifying its insulator‐to‐metal transition (IMT) temperature by up to ∼25 °C. Such area‐selective modification of metal oxides by direct writing using a FIB provides a simple, mask‐less route to the fabrication of optical structures, especially when multiple or continuous levels of doping or defect density are required.