Suppression of surfaces states at cubic perovskite (001) surfaces by CO2 adsorption

Abstract

By using first-principles approach, the interaction of CO₂ with (001) surfaces of six cubic ABO₃ perovskites (A = Ba, Sr and B = Ti, Zr, Hf) is studied in detail. We show that CO₂ adsorption results in the formation of highly stable CO₃-like complexes with similar geometries for all investigated compounds. This reaction leads to the suppression of the surfaces states, opening the band gaps of the slab systems up to the corresponding bulk energy limits. For most AO-terminated ABO₃(001) perovskite surfaces, a CO₂ coverage of 0.25 was found to be sufficient to fully suppress the surface states, whereas the same effect can only be achieved at 0.50 CO₂ coverage for the BO₂-terminated surfaces. The largest band gap modulation among the AO-terminated surfaces was found for SrHfO₃(001) and BaHfO₃(001), whereas the most profound effect among the BO₂-terminated surfaces was identified for SrTiO₃(001) and BaTiO₃(001). Based on these results and considering practical difficulties associated with measuring conductivity of highly resistive materials, TiO₂-terminated SrTiO₃(001) and BaTiO₃(001) were identified as the most prospective candidates for chemiresistive CO₂ sensing applications.