Electronic charge transfer between Au nano-particles and TiO_2-terminated SrTiO_3(001) substrate

摘要

The interaction between Au nano-particles and oxide supports is recently discussed in terms of the catalytic activities. This paper reports the electronic charge transfer between Au nano-particles and TiO_2-terminated SrTiO_3(001) substrate, which is compared with that for stoichiometric(S)-, pseudo-stoichi-ometric(S~*)- and reduced(R)-TiO_2(110) supports. We observed the photoelectron spectra of Au 4f, O 2s, Ti 3p, and Sr 4p lines and also measured the work functions for Au/oxides supports using synchrotron-radiation light. As the results, all the O 2s, Ti 3p, and Sr 4p lines for Au/SrTiO_3(001) show lower binding energy shifts in a quite same manner and abrupt increase in the work function is seen in an initial stage. This clearly evidences an electronic charge transfer from the substrate to Au probably due to a much larger work function of Au than SrTiO_3(001), which leads to an upward band bending (0.3 eV) just like a Schottky contact. Electronic charge transfers also take place at Au/S- and Au/S~*-TiO_2(110) and Au/ R-TiO_2(110) interfaces, where electrons are transferred from Au to S- and S~*-TiO_2 and from R-TiO_2 to Au, as predicted by ab initio calculations.