STM studies of the surface structure in cleaved Bi2Sr2CuO 6 + δ single crystals

Abstract

Low-temperature scanning tunneling microscopy (STM) was used tostudy the Bi-O plane ofBi2Sr2CuO 6 + δ (Bi-2201) single crystals cleavedin situ. The atomic-resolution STM images clearly show acommensurate modulated lattice structure. In contrast to theprevious STM data obtained at room temperature, the “missingatom rows” have been clearly seen at the ridges of themodulation. By comparing the low-temperature STM images ofBi-2201 and Bi-2212, we found that the modulation of theBi-O plane in these two materials originates fromthe “missing atom rows”. The atomic steps at the surface havealso been investigated at room temperature confirming that mosteasily exposed atomic layers in Bi-2201 areBi-O and Sr-O planes, as in Bi-2212.