Structure and restructuring of the atomic steps on Si(111)7×7

The termination of the lower terrace at the atomic steps on the Si(111)7×{}7 surface has been investigated with scanning tunneling microscopy (STM). It is proposed that seven positions of the steps relative to a 7×{}7 unit mesh of the end of the lower terrace are possible for each of two step directions, and ten of them have been observed in STM images. A rule for the termination at the steps is proposed. Structure and restructuring of the steps are described.