Periodically spaced CaF2 semi-insulating thin ribbons growth study on the Si(100) surface

Abstract

The use and the study of semi-insulating layers on metal and semiconductor surfaces have found continuous interest in the past decades. So far, the control of the sizes and growth location of the insulating islands on the substrates are either ill-defined or usually constrained to the use of evaporation masks, the size of which can easily exceed a few tens of nanometers. Here, we show that it is possible to grow self-organized periodically spaced thin ribbons of semi-insulating stripes on the bare Si(100) surface. The epitaxial growth of these structures is achieved by the evaporation of CaF₂ molecules on the silicon surface with a coverage of 1.2 monolayers. They are investigated via scanning tunneling techniques at low temperature (9 K). The obtained ribbons exhibit a surface bandgap of ∼3.2 eV as well as a resonant state at the central part of the ribbons at ∼2.0 eV below the Fermi level energy. The use of density functional theory allows suggesting a model structure of the observed ribbons and reproducing the experimental STM topographies. The formation of the thin ribbons is discussed, and we point out the influence of the mechanical forces inside and between the structures that may influence their periodicity.