Thermodynamically stable stoichiometric and higher oxidation states are known to be detrimental to the electrical and optical performances of Ag electrodes. In contrast, thermodynamically less stable or unstable suboxidation states entailing extreme O deficiencies are scarcely understood because the tenuous or null trace of O in suboxidized Ag domains is difficult to detect. This paper presents an experimental confirmation and numerical interpretation of the extreme suboxidation of Ag-layered electrodes and the influences of the post-growth reduction on their optoelectrical properties. A significant decrease in the electrical resistance of such suboxidized Ag layers is observed during post-growth storage under an ambient atmosphere with 40% relative humidity at 290 K, which is instantly implemented by covering the Ag layers with an atomically thin ZnO overlayer. The results indicate that the electrical improvement is attributed to the spontaneous post-growth reduction of Ag suboxides, which is driven by two sequential post-growth dynamics, namely, the strong segregation of atomic O originally incorporated in Ag suboxides to the outermost surface and the spillover of O to either the ambient atmosphere or ZnO overlayer. These findings provide a solution for implementing the optoelectrical and structural advantages of Ag electrodes by employing suboxidation without aftereffects.
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