Silver oxide is a p-type semiconductor that has potential applications as a sensing film or optical recording element. Silver is relatively inert towards oxygen and silver oxide is rather unstable. We studied the interactions of Ag with r-cut sapphire (@alpha@-Al@sub 2@O@sub 3@) surfaces at ambient temperature resulting from (i) thermal evaporation of Ag in UHV, (ii) evaporation of Ag in molecular O@sub 2@, and (iii) evaporation of Ag in the presence of an electron cyclotron resonance (ECR) oxygen plasma source. Pure Ag deposited in UHV grows with a random polycrystalline structure. However, when Ag is evaporated in a 10@super -4@ Torr molecular O@sub 2@ background, epitaxial Ag growth with (110) orientation is observed as determined by RHEED and XRD. No oxygen is incorporated in the film as measured by XPS and only a slight lattice mismatch at the Ag/sapphire interface is found suggesting that the adsorbed oxygen acts as a surfactant in influencing the Ag nucleation and surface transport. Using an ECR oxygen plasma, Ag@sub 2@O is formed with a structure being dependent on deposition rate; below 0.2 Å/s, (111) orientation is formed while at faster rates the oxide is amorphous. The Ag@sub 2@O films are unstable above ~180@super o@C. AFM observations of the evaporation process following vacuum annealing treatments indicate that the decomposition occurs through a nucleation process leaving behind metallic Ag clusters on the bare sapphire.