Sodium chloride on Si(100) grown by molecular beam epitaxy

Abstract

Sodium chloride (NaCl) films were grown on an Si(100)-(2 × 1) surface at near room temperature by molecular beam epitaxy (MBE). The atomic structure and growth mode of the prototypical ionic materials on the covalent bonded semiconductor surface is examined by synchrotron core-level x-ray photoemission spectrum (XPS), scanning tunneling microscopy (STM), and first-principles calculations. The Si 2p, Na 2p, and Cl 2p core-level spectra together indicate that adsorbed NaCl molecules at submonolayer coverage [i.e., below 0.4 monolayer (ML)] partially dissociate and form Si-Cl species, and that a significant portion of the dangling-bond characteristics of the clean surface remains after NaCl deposition of 1.8 MLs. The deposition of 0.65-ML NaCl forms a partially ordered adlayer, which includes NaCl networks, Si-Cl species, adsorbed Na species, and isolated dangling bonds. The STM results revealed that the first adlayer consists of bright protrusions which form small c(2 × 4) and (2 × 2) patches. Above 0.65 ML, the two-dimensional NaCl double-layer growth proceeds on top of the first adlayer.

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

“…S1 online). The adlayer is similar to the one observed by Chung et al 10 for the NaCl/Si(001) system. Taking their X-Ray photoemission results into account, we expect this adlayer to be composed of KCl molecules, Si-Cl species and K species.…”

“…The polar surfaces, however, possess uncompensated net dipole moments perpendicular to the surface, which leads to an increase of the surface free energy making them unstable 13 19 . The vast majority of studies of alkali-halide thin films grown on metals 20 21 22 23 24 25 26 27 and semiconductors 8 9 10 confirms this fact. However, if some specific requirements are fulfilled, NaCl(111) islands with the uppermost layer corresponding to a polar surface can also be grown, like on Al(111) and Al(001) 2 .…”

“…Earlier photoemission studies on KCl/Si(001) 9 and NaCl/Si(001) 10 at 330 K have shown that KCl and NaCl partially dissociate upon adsorption on the silicon surface to form Si-Cl bonds and adsorbed K and Na. We therefore assume that a similar process occurs during the KCl adsorption on the Si(111)7 × 7 substrate.…”

“…The growth of thin alkali halide films on metal 1 2 3 4 5 6 7 and, in a lesser extent, on semiconductor substrates 8 9 10 has been the subject of many studies for the last two decades. 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 .…”

Formation routes and structural details of the CaF1 layer on Si(111) from high-resolution noncontact atomic force microscopy data

“…Besides this application-oriented relevance, CaF 2 on Si(111) is of fundamental interest in understanding the growth and properties of heteroepitaxial systems and has consequently been intensively studied. Recently, also the growth of NaCl [12,13] (lattice mismatch with Si about 4%) and KCl [14,15] (lattice mismatch with Si more than 10%) thin films on surfaces of silicon has been investigated. A short review summarizing the extensive characteristics of CaF 2 deposited on Si(111) will be given in Sec.…”