An influence of the dopant concentration on polycrystalline Si grain structure, electronic structure and dopant segregation in 800 °C and 30 min annealing is investigated. Barrier height images and topographies of arsenic implanted polycrystallinesiliconsurface are obtained using tunneling barrier height imaging (TBI) and scanning tunneling microscopy(STM) with the vacuum pressure less than 5×10−7 Torr. As results, a conduction band bending caused by the arsenic ion implantation can be observed by the TBI. A comparison of the TBI image with the STM image can identify whether region is implanted or nonimplanted. In addition, dopant segregation structures at the grain boundary can be found out. With dopant concentration, 101 4 cm−2 As+ implanted polycrystallinesilicon grain structures of 4–80 nm size grow large.