Using the four-point probe method,we studied in sit tt the surface conducti
vity of submonolayer Au/Si(100) and Au/Si(111) system. Electrical measureme
nts showed that surface phases act as an additional conductivity channel. T
he value of conductivity of this channel depends on the structural and elec
tronic properties of the surface phases. Destruction of the surface phase o
f atomically clean silicon by adsorbed Au atoms reduces the conductance of
the substrate.