In situ Hall measurements of Fe and Cr submonolayers on Si(111) of n- and p-type conductivity

By the method of in situ Hall effect measurements at room temperature, it w as shown that the formation of a clean Si(111)(7 x 7) surface at high tempe rature annealing (T = 1250 degrees, t = 120-180 s) of n-type conductivity s ilicon results in a change of the majority carriers on a surface. But on a surface of p-type conductivity silicon it results in the formation of a hol e accumulated layer. Various dynamics of changes in the Hall voltage and re sistivity voltage within the limits of the first monolayer of room temperat ure adsorption of iron and chromium on substrates with a p-n junction and w ith a hole accumulated layer are not connected with conductivity along an a bsorbed layer. To understand the mechanism of conductivity in a system adso rbed layer Fe(Cr)/Si(111)(7 x 7), it is necessary to take into account two effects: (a) destruction of the superstructure Si(111)(7 x 7); (b) formatio n of donor-type surface states of Fe(Cr) in the band gap of silicon. Destru ction of the localized surface states of the superstructure Si(111)(7 x 7) plays the greatest role, when the density of donor-type surface states is v ery small. It corresponds to adsorption of Cr on Si(111) of p-type conducti vity. The greatest contribution of donor-type surface states to the conduct ivity of the surface space-charge layer was observed with adsorption of Fe on Si(111) of n-type conductivity. Conductivity through the adsorbed iron ( chromium) layer began with a thickness more than three monolayers.