Adsorption of Cyclic (Alkyl) (Amino) Carbenes on Monohydride Si(001) Surfaces: Interface Bonding and Electronic Properties

Abstract

The adsorption of cyclic (alkyl) (amino) carbenes on the monohydride Si(001) surface is explored within density-functional theory. Two different adsorption mechanisms are investigated: the carbene insertion in Si−H bonds and the binding to a surface defect with missing hydrogen. The relative stability of these configurations depends on the hydrogen chemical potential, i.e., the surface preparation conditions as well as on the molecular side groups. The latter are also found to decisively influence the molecular diffusion. Some adsorption configurations are found to give rise to electronic states within the silicon bulk band gap. A sizable reduction of the work function is found upon molecular adsorption.

Influence of the defect density on the ordering of an NHC monolayer on a silicon surface

“…45 Although studies investigated the self-assembly of CAAC molecules on Au(111), Ag(111), and Cu(111) surfaces, 3,46 on semiconductors only H-terminated Si substrates have been investigated to date. 33,47 In this work, we investigate the adsorption of cyclohexyl CAAC (cyCAAC) (see Fig. 1(c)) on the Si(111)-B surface using scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED), accompanied by X-ray photoelectron spectroscopy (XPS) to determine the work function change upon the adsorption of the molecules.…”

“…45 Although studies investigated the self-assembly of CAAC molecules on Au(111), Ag(111), and Cu(111) surfaces, 3,46 on semiconductors only H-terminated Si substrates have been investigated to date. 33,47…”

Elucidating the Lability and Diversity of Self-Assembled Structures of N-Heterocyclic Carbenes at the Liquid/Metal Interface

“…While the properties of NHC-functionalized metals are to a large extent associated with the binding and organization of NHCs on the surface, − a molecular-level characterization of NHCs on surfaces is necessary. − Scanning tunneling microscopy (STM) studies at the vacuum/solid interface have made great progresses in getting in-depth insights into the unique characteristics of NHCs on metal surfaces, , for instance, the complexation between multiple NHC ligands and a metal adatom, the ballbot-type motion of and the unidirectional rotation of the NHC molecule on the surface. − Also, regular self-assembled monolayers (SAMs) of NHCs at the solid surface of the metal, − metal oxide, and silicon − have been obtained through the sublimation of NHC–CO 2 precursors in vacuum chambers. However, ordered monolayers of NHCs were usually obtained in the absence of a liquid phase.…”