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The oxidation rate of silver films by atomic oxygen has been measured by using a gravimetric method. The rate of the reaction has been followed as a function of temperature, film thickness, and the atomic oxygen concentration. The oxidation can be divided into three phases. During the first phase, the process is first-order in atomic oxygen concentration, and the product is AgO. The process is described in terms of a moving boundary model, where the diffusion rate of oxygen atoms is high in the oxide layer and nil in the elemental silver layer. The diffusion coefficient for oxygen atoms in silver oxide is 2.5 X 10~13 cm2/s at 298 K. The second phase is much slower, and it is independent of the atomic oxygen concentration. The stoichiometric formula for the product is Ag02, and its formation is inhibited by increasing the temperature from 290 to 313 K. Upon prolonged exposure to atomic oxygen, phase 3, the silver films are oxidized to a stoichiometric formula Ag03. These products are stable to several hundred kelvin above ambient temperature. Silver films have a rapid affinity for atomic oxygen, and complete penetration of the films as thick as 200 nm has been demonstrated.

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