Periodically Spaced CaF$_2$ Semi-Insulating Thin Ribbons Growth Study on the Si(100) Surface

TL;DR

This study demonstrates the self-organized growth of periodically spaced semi-insulating CaF₂ ribbons on Si(100) surfaces, revealing their electronic properties and proposing a structural model through combined experimental and theoretical analysis.

Contribution

It introduces a novel method for growing self-organized, periodically spaced CaF₂ ribbons on silicon, advancing control over insulating layer patterning at the nanoscale.

Findings

Ribbons exhibit a ~3.2 eV surface bandgap.

Resonant state observed at ~2.0 eV below Fermi level.

Density functional theory supports the proposed ribbon structure.

Abstract

The use and the study of semi-insulating layers on metals and semiconductors 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 substrate is either ill-defined or usually constrained to the use of evaporation masks which size can easily exceed tenth 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 obtained by the evaporation of CaF$_2$ molecules on the silicon surface with a coverage of 1.2 monolayers. They are investigated via scanning tunneling techniques at low temperature (9K). 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 the 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.