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

Evaporation of Ag in the presence of an electron cyclotron resonance (ECR) oxygen plasma was used to deposit Ag2-xO 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 Ag2O stoichiometry, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis indicates that the Ag2-xO films are not single phase but contain signatures of coexisting Ag2O and AgO components. XRD shows that the lattice matching with the r-plane sapphire substrate causes the Ag2O phase to grow with < 002 > heteroepitaxial crystallites coexisting with crystallites having < 111 > normal and random in-plane orientation. The AgO phase also forms with crystallites having < 002 > heteroepitaxy as well as crystallites with < 111 > normal and random in-plane orientation. The mixed phase Ag2-xO films exhibit approximately 77% optical transmission over the visible range (500 nm to 700 nm) and have a single absorption edge near 3.3 cV. Four-point van der PauA, conductivity and Hall effect measurements indicate that the A92-0 films are p-type with a conductivity on the order of 3 x 10(-3) Omega(-1) cm(-1). (c) 2007 Elsevier B.V All rights reserved.