Hybrids of Organic Molecules and Flat, Oxide-Free Silicon: High-Density Monolayers, Electronic Properties, and Functionalization

Abstract

Since the first report of Si-C bound organic monolayers on oxide-free Si almost two decades ago, a substantial amount of research has focused on studying the fundamental mechanical and electronic properties of these Si/molecule surfaces and interfaces. This feature article covers three closely related topics, including recent advances in achieving high-density organic monolayers (i.e., atomic coverage >55%) on oxide-free Si(111) substrates, an overview of progress in the fundamental understanding of the energetics and electronic properties of hybrid Si/molecule systems, and a brief summary of recent examples of subsequent functionalization on these high-density monolayers, which can significantly expand the range of applicability. Taken together, these topics provide an overview of the present status of this active area of research.

Copper-Free Click Biofunctionalization of Silicon Nitride Surfaces via Strain-Promoted Alkyne–Azide Cycloaddition Reactions

“…The data are in good agreement with an XPS study of heterocycles introduced after a Cu-assisted azide−alkyne cycloaddition reaction. 47 To study in more detail the reactivity of the cyclooctyne on the surface, the progress of the SPAAC reaction was followed by means of XPS and static water contact angle measurements. The reaction time for grafting azide 8 on films S7 was varied.…”

“…52 Additionally, such "clickable platforms" were applied as an efficient strategy for PEGylation of the surfaces 53 and for immobilization of biomolecules like peptides, 54 oligonucleotides, 52 and mannose moieties. 47,55 Although a robust, orthogonal, and efficient reaction, CuAAC on a surface is sometimes carried out under conditions that are incompatible with the group to be attached or the envisioned application. For example, microwave irradiation, 56 heating for prolonged time, 51 and high concentrations of copper ions may be detrimental for the attached moieties.…”

Effect of Molecule–Surface Reaction Mechanism on the Electronic Characteristics and Photovoltaic Performance of Molecularly Modified Si

“…Organic monolayers (MLs) on oxide-free Si surfaces 1 have been studied extensively as a viable and effective tool to control the electronic properties of Si (see ref (2) and references therein). The basic idea that lies at the heart of these studies is that by combining molecular functionality with the robustness of Si technology we can create hybrid (organic–Si) systems that will extend and improve the possibilities of existing devices and provide options for new ones.…”

Rapid Surface Functionalization of Hydrogen-Terminated Silicon by Alkyl Silanols

“…32 In this regard, a variety of surface modification methods has been investigated with the aim of preserving the near-ideal electrical and electronic properties of H-terminated Si surfaces, while providing a handle for further functionality. 11,18,33 Typical modification strategies based on sonochemistry, 34 thermal activation, 35,36 use of catalysts or Lewis acids, 37 or visible light irradiation, 38 have been widely studied, but often require long reaction times (2–18 h). Alternative, more rapid (10–30 min) grafting approaches based on the use of UV light (254 nm) have been reported, 39−41 but these, of course, limit other substituents in the molecule to those that are not photoreactive at this short wavelength.…”