Characterization of (In,Pb)/Si(111): Tuning normal and lateral atom distributions in mixed metal systems

Abstract

The growth mode, thermal stability and long range order of In on the Si(111)−α(√3 × √3)−Pb reconstructed surface were investigated by Low Energy Diffraction and X−ray Photoelectron Spectroscopy measurements combined with first−principles Density Functional Theory calculations (DFT). It is shown that indium atoms have tendency to exchange their positions with the lead surfactant resulting in the formation of mixed (In,Pb) heterostructure at elevated temperatures (around 470 K). Moreover, with further temperature increase new metastable In–Pb surface alloys are sequentially observed as the fraction of Pb adatoms decreases. DFT simulations confirmed the experimental findings yielding that not only Pb segregation to the topmost layer is energetically favourable, but also its desorption is expected to occur at lower temperature than the desorption of In due to lower binding energy of the former.