STM studies of the surface structure in cleaved single crystals

¹ National Laboratory for Superconductivity, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences P.O. Box 603, Beijing 100080, PRC
² Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven Celestijnenlaan 200 D, B-3001 Leuven, Belgium
³ Max-Planck-Institut für Festkorperforschung Heisenbergstrasse 1, D-70569 Stuttgart, Germany

Received: 11 October 2002
Accepted: 13 December 2002

Abstract

Low-temperature scanning tunneling microscopy (STM) was used to study the - plane of (-2201) single crystals cleaved in situ. The atomic-resolution STM images clearly show a commensurate modulated lattice structure. In contrast to the previous STM data obtained at room temperature, the “missing atom rows” have been clearly seen at the ridges of the modulation. By comparing the low-temperature STM images of -2201 and -2212, we found that the modulation of the - plane in these two materials originates from the “missing atom rows”. The atomic steps at the surface have also been investigated at room temperature confirming that most easily exposed atomic layers in -2201 are - and - planes, as in -2212.