Adsorption and desorption of Se on Si(100) 2 x 1: surface restoration

This work entails a study of the adsorption of elemental Se on the reconstructed Si(100)2 x 1 surface. The investigation took place in an ultra high vacuum (UHV) by low energy electron diffraction (LEED), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS) and work function (WF) measurements. The adsorption of one monolayer (1 ML) of Se at room temperature (RT) causes the transition of the reconstructed Si(100)2 x 1 surface to its original bulk terminated Si(100)1 x 1 configuration, while Se adatoms form a 1 x 1 structure by breaking the Si-Si dimer bonds,The Si-Se bond is strong (E-b = 2.97 eV/atom), resulting in the formation of a SiSe compound. Above 1 ML, Se forms a SiSe, compound with E-b = 2.67 eV/atom. The heating that follows causes the desorption of Se up until 1000 K, where Theta (Se) = 0.5 ML, and the Si(100)1 x 1 structure is changed back to the reconstructed Si(100)2 x 1 with the Se forming a 2 x 1 structure. The models of Se(1 x 1)/Si(100)1 x 1 and of the Se(2 x 1)/Si(100)2 x 1 structures are given. (C) 2000 Elsevier Science B.V. All rights reserved.