An STM study of desorption-induced thallium structures on the Si(111) surface

The scanning tunneling microscopy is used to study morphology of a Tl adlayer in various stages of Tl desorption from the Si(111) surface. Transition from the Si(111)/(1 × 1)-Tl structure through the (√3 × √3)R30° mosaic phase to domains of metastable Si reconstructions is observed. Silicon substitutional atoms are found to be intrinsic to the (√3 × √3)R30° structure. The temperature dependence of the amount of residual Tl atoms on the surface is successfully fitted by a model using the first order desorption. The same desorption energy of (2.1 ± 0.3) eV and frequency prefactor 5 × 1014 ± 2 s− 1 during all stages of the desorption are sufficient for the fitting. It is concluded that bonding of Tl in both (1 × 1) and (√3 × √3) configurations is of the same nature.