THERMALLY ACTIVATED RECONSTRUCTION IN YB-SI(111) THIN-FILM STRUCTURES

The electronic properties and mechanisms of formation of Yb-Si(111) th in-film structures, produced by room-temperature deposition of Yb atom s on the Si(111)7 x 7 surface are studied by Auger electron and LEED s pectroscopy and the contact potential difference method. A study is al so made of the effect of heating to 800 K on the properties of these s tructures. The interface is shown to form by the Stransky-Krastanov me chanism. Heating the Yb-Si(111) system is found to result in a very hi gh (up to 1 eV) increase of the work function for all Yb atom concentr ations on the silicon surface. In the adsorption stage, this increase is due to the growth of 2D ytterbium domains, which is accompanied by the formation of polarized domains from the silicon surface atoms with dangling valence bonds. The dipoles are oriented in such a way that t heir formation reduces the total energy of the Yb-Si(111) system and i ncreases the work function. In the stage of silicide formation, the in crease of the work function under heating is ultimately due to the app earance of a layer of silicon atoms on the Yb-Si(111) surface. (C) 199 7 American Institute of Physics.