Drift of adatoms on the (111) silicon surface under electromigration conditions

The existence of the drift of adatoms on the surface that is induced by an electric current heating a sample under the conditions of sublimation, homoepitaxial growth, and quasiequilibrium on the (111) silicon surface at temperatures above $1050^\circ$C has been shown by in situ ultrahigh-vacuum reflection electron microscopy and ex situ atomic-force microscopy. It has been found that the direction of the drift of adatoms is independent of the supersaturation value on the surface. Under these conditions, the drift of adatoms occurs towards underlying terraces, i.e., at $1050$–$1240^\circ$C at the resistive heating of the sample by step-up direct electric current and at $1250$–$1350^\circ$C by step-down current. The presence of the drift of adatoms indicates that adatoms have an effective charge whose value at $1280^\circ$C is estimated as $0.07\pm 0.01$ of the elementary charge.