KCl ultra-thin films with polar and non-polar surfaces grown on Si(111)7 × 7.

Igor Beinik,Margrit Hanbücken,Clemens Barth,Laurence Masson

doi:10.1038/srep08223

Abstract

The growth of ultra-thin KCl films on the Si(111)7 × 7 reconstructed surface has been investigated as a function of KCl coverage and substrate temperature. The structure and morphology of the films were characterized by means of scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. Detailed analysis of the atomically resolved STM images of islands grown at room and high temperatures (400 K–430 K) revealed the presence of KCl(001) and KCl(111) islands with the ratio between both structures depending on the growth temperature. At room temperature, the growth of the first layer, which covers the initial Si(111)7 × 7 surface, contains double/triple atomic layers of KCl(001) with a small fraction of KCl(111) islands. The high temperature growth promotes the appearance of large KCl(111) areas, which are built up by three atomic layers. At room and high temperatures, flat and atomically well-defined ultra-thin KCl films can be grown on the Si(111)7 × 7 substrate. The formation of the above mentioned (111) polar films is interpreted as a result of the thermally activated dissociative adsorption of KCl molecules on Si(111)7 × 7, which produces an excess of potassium on the Si surface.

Highlights

The growth of ultra-thin KCl films on the Si(111)[7 3 7] reconstructed surface has been investigated as a function of KCl coverage and substrate temperature
The structure and morphology of the films were characterized by means of scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions
In conclusion, we have conducted an in-situ characterization of the atomic structure and morphology of KCl films grown on Si(111)[7 3 7] by means of STM

Summary

Introduction

The growth of ultra-thin KCl films on the Si(111)[7 3 7] reconstructed surface has been investigated as a function of KCl coverage and substrate temperature. Apart from a fundamental interest in such films, an emerging topic concerns the formation of supramolecular[11,12,14] and covalent[15] assemblies on such substrates for rising applications in organic electronics or molecule-based sensing devices since it has been recently shown that ultrathin NaCl layers grown on metal surfaces can be beneficially used for the efficient electronic decoupling of adsorbates from the conductive substrates[16,17,18] For this purpose, the formation of atomically well-defined flat layers with a low density of defects is of prime importance. We show that flat and atomically well-defined ultra-thin KCl layers can be epitaxially grown on Si(111)[7 3 7]

Methods

Results

Discussion

Conclusion