In Situ Hall Measurements of Fe and Cr Submonolayers on Si(111) of n- and p-Type Conductivity

Abstract

By the method of in situ Hall effect measurements at room temperature, it was shown that the formation of a clean Si(111)(7×7) surface at high temperature annealing (T=1250°, t=120–180 s) of n-type conductivity silicon 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 hole accumulated layer. Various dynamics of changes in the Hall voltage and resistivity voltage within the limits of the first monolayer of room temperature adsorption of iron and chromium on substrates with a p–n junction and with a hole accumulated layer are not connected with conductivity along an absorbed layer. To understand the mechanism of conductivity in a system adsorbed layer Fe(Cr)/Si(111)(7×7), it is necessary to take into account two effects: (a) destruction of the superstructure Si(111)(7×7); (b) formation of donor-type surface states of Fe(Cr) in the band gap of silicon. Destruction of the localized surface states of the superstructure Si(111)(7×7) plays the greatest role, when the density of donor-type surface states is very small. It corresponds to adsorption of Cr on Si(111) of p-type conductivity. The greatest contribution of donor-type surface states to the conductivity 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.