Atomic and Electronic Processes during the Formation of an Ionic NaCl Monolayer on a Covalent Si(100) Surface

Abstract

An atomic layer of stoichiometric NaCl was formed on a covalent Si(100) surface after two successive half-reactions at room temperature. The first half-reaction due to Cl 2 exposure generates a square array of Cl adatoms with a distance close to that in a NaCl(100) surface plane. By utilizing scanning tunneling microscopy (STM), corelevel photoemission spectroscopy, and ab initio density functional theory (DFT) calculations, it was found that progressive deposition of Na in the second-half reaction results in surface-supported Na 3 Cl clusters, onedimensional cluster chains, and (2 × 2) patches, and eventually turns the Cl-adlayer into a single-terrace, wavy NaCl layer at one monolayer Na coverage. The grown NaCl monolayer rolls over atomic steps like a carpet and covers the entire surface.The atomic and electronic structure of the topmost Si layer underneath the NaCl layer resembles that of the initial silicon surface layer with buckled dimers. Results of the comprehensive investigation together suggest that an ionic NaCl monolayer is very weakly bonded to the covalent substrate and appears nearly free-standing.

Separation of the attractive and repulsive contributions to the adsorbate–adsorbate interactions of polar adsorbates on Si(100)

“…The p(2 × 2) and c(4 × 2) structures consisting of alternating dimers are seen in the STM images and the intrinsic properties of the clean Si(100) become quite complex [29,30]. As reported elsewhere [31], our calculations showed that the buckled phase is favored by 0.08 eV per (1 × 1) supercell over the symmetric (2 × 1) phase and that other structure parameters are consistent with previous findings [26,28,32].…”

Nanostripe Pattern of NaCl Layers on Cu(110)

“…The atomic-scale imaging of the metal-supported insulating layers in scanning tunneling microscopy (STM) is also possible, due to mixing of electronic states of the metal and insulating film for thicknesses 1 nm. A suitable dielectric material for molecular nanoscience purposes is NaCl [1,2,4,7,8], whose popularity is based on its ease of thin film deposition by vacuum sublimation of NaCl molecules from solid sodium chloride, and on the formation of well-defined one to three monolayer (ML) thick islands on low-index surfaces of noble [9][10][11][12][13] and simple metals [14], and semiconductors [15]. The NaCl layers grow in (100) orientation irrespective of the substrate orientation, and this is indicative of a weak overlayer-substrate coupling.…”

“…A in [001] direction and 3:83 AE 0:05 A in [110] direction to be compared with values of 3.96 Å for bulk NaCl and 3.56 Å for a free ML [15] (the interaction with the surface counteracts the shrinking due to reduced dimensionality [25]); this yields a [ð3=2Þ a½110 Â ð11=10Þ a½001 ] overlayer lattice in terms of the Cu(110) unit cell vectors. In Fig.…”

Encapsulation of epitaxial silicene on ZrB2 with NaCl

“…This was previously observed by Chung et al upon deposition of NaCl on Si(100), with a chemical shift of +0.9 eV for Si-Cl species relative to the bulk Si 2p 3/2 peak. 20,21 Matsuo et al studied the surface reaction of molecular and atomic chlorine on Si(100) and Si(111) and found not only Si-Cl by exposure to molecular chlorine but also Si-Cl x (x = 2-4) by exposure to atomic chlorine. 22 They reported Si-Cl at a binding energy of 100.5 eV and an additional chemical shift of +1 eV for every additional chlorine bond.…”