Inorganic oxide articles with thin, durable anti-reflective structures

An article that includes: an inorganic oxide substrate having opposing major surfaces; and an optical film structure disposed on a first major surface of the substrate, the optical film structure comprising one or more of a silicon-containing oxide, a silicon-containing nitride and a silicon-containing oxynitride and a physical thickness from about 50 nm to less than 500 nm. The article exhibits a hardness of 8 GPa or greater measured at an indentation depth of about 100 nm or a maximum hardness of 9 GPa or greater measured over an indentation depth range from about 100 nm to about 500 nm, the hardness and the maximum hardness measured by a Berkovich Indenter Hardness Test. Further, the article exhibits a single-side photopic average reflectance that is less than 1%.