Characterization of oxide nanocomposites formed at annealed TiN/SnS2 heterostructure thin film

Abstract The compositional evolution of TiN/SnS2 thin films exposed to post-deposition annealing (PDA) at various O2 pressures (P(O2) = 0, 0.1, 1, 2 and 5 Torr) was examined using X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy and transmission electron microscopy. All the results of the analyses showed that the PDA oxidized the hetero-structured films to form SnO2+TiO2 nanocomposites throughout the film, driving out sulfur ions. The chemical and microstructural evolution according to the oxidation was confirmed by TEM and the energy-dispersive spectroscopy analyses. The XAS analysis particularly showed that with increasing P(O2), the composition of the nanocomposites changed and the microstructure of the titania in the nanocomposites evolved from an anatase to a rutile structure gradually. The conduction band structure also changed in accordance with this microstructural evolution. Electrical measurements on devices with the oxidized SnS2/TiN heterostructure and additional thick TiN metal electrode, further showed that the contact resistance decreased dramatically after the PDA. This implies that the formation of SnO2+TiO2 at the interface between semiconducting SnS2 and metallic TiN can be an effective way to improve the metal-semiconductor contacts.