In phosphate solution at pH 4.6, in situ STM images on Au(111) were different in the potential regions where the Au(111) interface is taken to be free from phosphate adsorption and where the upd Zn is formed. In the former region, the observed STM image was Au(111)(1 x 1), and in the upd region, the image was taken to be (root 3 x root 3)R30 degrees. As the phosphate is expected to adsorb on upd Zn by oxidative reaction, it is suggested that the latter image is due to the adsorbed phosphate species formed on upd Zn at Au(111) by upd induced adsorption.