Structure, conductivity, and optical absorption of Ag2−xO films

Abstract Evaporation of Ag in the presence of an electron cyclotron resonance (ECR) oxygen plasma was used to deposit Ag 2− x O films with a range of stoichiometries onto r-plane sapphire substrates. A quartz crystal oscillator (QCO) was used to accurately measure the silver and oxygen arrival rates and establish the O/Ag flux ratio needed to produce films with nominal Ag 2 O stoichiometry. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicates that the Ag 2− x O films are not single phase but contain signatures of coexisting Ag 2 O and AgO components. XRD shows that the lattice matching with the r-plane sapphire substrate causes the Ag 2 O phase to grow with heteroepitaxial crystallites coexisting with crystallites having normal and random in-plane orientation. The AgO phase also forms with crystallites having heteroepitaxy as well as crystallites with normal and random in-plane orientation. The mixed phase Ag 2− x O films exhibit approximately 77% optical transmission over the visible range (500 nm to 700 nm) and have a single absorption edge near 3.3 eV. Four-point van der Pauw conductivity and Hall effect measurements indicate that the Ag 2− x O films are p-type with a conductivity on the order of 3 × 10 − 3 Ω − 1 cm − 1 .