In the last decade,great attention has focused on LaAlO3/SrTiO3(LAO/STO) interface andmany unexpected and novel properties are revealed [1].Of particular importance to thesurfaces and interfaces for realistic applications are surface defects and cation intermixing [2].Oxygen vacancies [3] or cation vacancies [4] such as Sr vacancies have been proposed to beresponsible for the tuned electron density at the interfaces in different oxygen atmosphere.