Using low energy electron diffraction (LEED) and the four-point probe method for measurements of electrical conductivity in situ the formation of the single-domain Si(111)5 x 2-Au surface phase has been studied. This surface phase is formed by surface diffusion of gold atoms from a gold strip with thickness of about 10 monolayers. The changes in surface conductivity for Si(111)5 x 2-Au single-domain surface phase are evaluated in comparison with the Si(111)5 x 2-Au three-domain surface phase formed by deposition of 0.5 monolayers of Au and subsequent annealing. (C) 2004 Published by Elsevier B.V.