Heterophase Interface and Surface Functionalization of TiO_x/TiSi_x Metastable Nanofilms

Abstract

In this paper, topographically asymmetric TiOx/TiSix metastable ultrathin (nano)films on SiO2/Si(100) are produced by controlling interface reactions through ion beam synthesis. The film growth process involves a dual ion beam system, combining Ar+ sputtering a Ti target and in situ postirradiation (Ar+ + H2+ ion etching) at normal incidence to modify the surface morphology. The film's production and characterization are challenging due to the formation of a complex mixed interface+layers (heterophases) containing nanocrystalline and amorphous compounds of Ti and Si. The results for different ion etching times (0–600 s) are systematically presented and analyzed. With the experimental+theoretical information, it is possible to deduce that the heterophase interface is originated by oxide intermixing in combination with the formation of titanium silicides taking place at the early stages of growth. The reactivity of oxygen and hydrogen species is the dominating factor influencing the metastable film growth mediated by solid‐state phase reactions. Given its crucial role at the (Ti/Si):O interface, the chemical route and control of intrinsic defects (non‐stoichiometry) are defined by domain ordering mechanisms followed by surface restructuring. In view of their main characteristics, taken altogether, the current functional metastable films represent a promising alternative for high‐performance photonic and optoelectronic applications.