Tantalum- and Silver-Doped Titanium Dioxide Nanosheets Film: Influence on Interfacial Bonding Structure and Hardness of the Surface System

Surface modification via advanced technologies to manufacture durable coatings for increasing mechanical, chemical, and biological efficacy is an active research area for biomedical industries. The surface and coating/substrate interface play important roles regarding the biological performance. Precise knowledge concerning the interfacial layer in heterostructures is not well understood because of a lack of in situ characterization. Here, we investigate interfacial bonding structures by an electronic model in (i) tantalum-coated titanium alloy (Ta/Tialloy) and (ii) tantalum–silver-coated titanium alloy (TaAg/Tialloy) bilayer interfaces. The tantalum and tantalum–silver thin films were grown onto Tialloy substrates in a high-vacuum system by magnetron sputtering. We use X-ray photoelectron spectroscopy to probe the electronic structure of the so-formed Ta/Tialloy and TaAg/Tialloy bilayer interfaces. The results demonstrate that the thin-film/substrate interfaces exhibit different bonding characteristics. The TaAg/Tialloy exhibits two semiconductor phases in the interfacial layer with a band gap that is larger than that for the Ta/Tialloy. The large band gap semiconductors that evolve at the interface of the TaAg/Tialloy, as well as the elements with high electronegativity in the overlayer, increase the satellite peak intensity in the interface layer and generate interface polarization. There is an associated increase in the interfacial bonding strength by ionic bonding formation that is determined by measuring the hardness of this material system.