Combined effect of ion bombardment and nitrogen incorporation on structure, mechanical and optical properties of amorphous Ge2Sb2Te5 films

Abstract

Although the structural, mechanical and optical properties of amorphous Ge2Sb2Te5 films are very important for many practical applications, how to control and improve these properties has not yet been well explored. Here, we find that ion bombardment and nitrogen incorporation exert significant impacts on the structure, hardness and Urbach tail width (E0) of amorphous Ge2Sb2Te5 films. The underlying physical mechanisms are revealed through combinations of experiments and theoretical calculations. Ion bombardment causes crystallization of amorphous Ge2Sb2Te5 films, while nitrogen incorporation induces the transition from the crystalline film to amorphous film again, because nitrogen incorporation renders the formation of strong Ge-N bond, which increases the crystallization activation energy. Ion bombardment improves the hardness of the films by 18.5% and nitrogen incorporation can further improve the hardness by 39.2%. Both the ion bombardment and nitrogen incorporation significantly change E0 of films, which has not been previously reported. The underlying mechanism is that ion bombardment causes variation in disorderliness of film and nitrogen incorporation causes decrease in dielectric coefficient. Therefore, the combination of ion bombardment and nitrogen incorporation can finely control the crystallization, hardness and E0 of amorphous Ge2Sb2Te5 films, which provides a new research strategy to improve the structure and properties.