Molecular beam epitaxy growth of IrO2 using plasma-only oxidation

Growth of IrO2 films via molecular beam epitaxy (MBE) using an oxygen plasma as the sole oxidant is demonstrated for the first time. We investigate the oxidizing conditions required for IrO2 by characterizing the species present in the plasma using optical emission spectroscopy and comparing the thermodynamic equilibrium between Ir/IrO2 under atomic and molecular oxygen. Across the pressure range accessible, monatomic oxygen was the primary reactive species present in the plasma. IrO2 films were grown under varying Ir flux, oxygen pressure, and substrate temperature to understand growth thermodynamics and kinetics. Structural characterization assessed film phase and composition, crystallinity, strain, and surface morphology. The optimized films from this study validate plasma-only reactive growth by MBE as a successful method for growing IrO2.