Corrosion of titanium-nitride encapsulated silver films exposed to a H₂S ambient

Annealing of a Ag(19 at.% Ti)/SiO₂/Si(100) structure in a flowing NH₃ ambient resulted in the encapsulation of a silver film by a surface TiN of ∼20 nm and an interfacial TiOATi₅Si₃ bilayer. TiN is formed by the reaction of the segregated Ti and the NH₃ ambient. The interfacial structure is a result of the dissociation of SiO₂ into free O and Si followed by the reaction of it with Ti. To evaluate the effectiveness of the TiN encapsulation to protect the Ag against corrosion, the encapsulated silver films were annealed in a severe H₂S ambient for 30 min, at temperatures ranging from 100-500°C. At temperatures ≥300°C silver diffuses to the surface to react with the H₂S to form a non-uniform layer of rhombic and cubic Ag₂S crystallites. The unprotected Ag(Ti) alloys and pure Ag on SiO₂ corroded at 100°C, when annealed under the same conditions.