Quasi-long range ordered hole-adatoms pairs on SrTiO$_{3}$(110)-(4$\times $1) surface*

The surface structure of transition metal oxides (TMOs) has been an important issue for chemistry and photocatalysis. We studied the surface of SrTiO$_{3}$, which is a wide-gap semiconductor and has been believed useful for photo-induced water splitting. Specifically we focused on the (110) surface that bears intrinsic instability of reconstruction due to the surface polarity. The monophased (4$\times $1)-reconstructed surface was obtained with the treatment of argon ion sputtering followed by annealing in ultra high vacuum. More interestingly, we observed a (4$\times $10) quasi-long range ordered hole-adatom structure. The atomic configuration was identified by both experimentally adsorbing additional Sr atoms and density functional calculations. The ordering of the hole-adatom pairs was robust since its formation effectively released the stress on (4$\times $1)-reconstructed SrTiO$_{3}$(110) surface. Such a surface with ordered defects served as a good template for the guided growth of noble metal nanoclusters with controlled size and density.