Using a surface potential measurement method attached to non-contact atomic force microscope (nc-AFM), electrostatic potential at the step edges of the Si(1 1 1)7 x 7 surface is measured and found to be higher than that of terrace. The obtained result is opposite to the cases of Au and Cu(1 1 1) surfaces, where work function measurement with scanning tunneling microscopy (STM) revealed reduced work function at the step edges. Atomically resolved images taken in various modes with nc-AFM are also presented. (C) 2002 Elsevier Science B.V. All rights reserved.