Reversible electromigration of thallium adatoms on the Si(1 1 1) surface

By means of low-energy electron diffraction (LEED), we found a reversible structural change of (1×1)↔(3×3) on thallium (Tl) adsorbed Si(1 1 1) surfaces by switching the polarity of applied DC voltage for heating the sample. It was shown in the literature that Tl adatoms are located on the T4 sites of the bulk-terminated surface both in the (1 × 1) and (3×3). It is clarified that the structural change is caused by the electromigration of the Tl adatoms. Tl atoms migrate towards the cathode, being induced by the electric field (10-20 V/cm). We discussed an atomic process of the electromigration.