The characteristics of several reactively sputtered AgOx films, prepared at different oxygen flow ratios, with and without ZnS-SiO2 protective layers have been examined. For the as-deposited AgOx films, the amount and size of Ag clusters decreased, and the constituent phase of AgOx gradually transferred from pure Ag2O, to a mixture of Ag2O and AgO, then to pure AgO, as the oxygen flow ratio was increased. After annealing, the reduction of AgO into Ag2O and decomposition of Ag2O into Ag and O2 took place, and the decomposed Ag elements would diffuse outward and precipitate small silver particles on the surface of ZnS–SiO2 protective layers. The chemical decomposition of AgOx film confined by ZnS–SiO2 protective layers was confirmed to be an irreversible process. The super-resolution near field effect becomes significant only when the super-resolution near-field structure (super-RENS) disk with an AgOx mask layer prepared at oxygen flow ratios above a threshold value, where AgOx film consists of Ag2O or AgO phase.