Highly Stable Si−C Linked Functionalized Monolayers on the Silicon (100) Surface

Abstract

Monolayers that are bonded via a covalent Si−C bond are prepared on a silicon(100) surface by reaction of a 1-alkene with the hydrogen-terminated silicon surface. The monolayers have been analyzed by infrared spectroscopy, X-ray reflectivity, and water contact angle measurements and display a remarkably high thermal stability. The reaction also works well for ω-functionalized 1-alkenes, provided that the functional group is properly protected. After formation of the monolayer, the protecting group can be easily removed without noticeable disturbance of the monolayer integrity, and the now reactive sites at the monolayer can be used for further functionalization, as has been shown in the case of ester-protected alcohol and carboxylic acids. Functional groups that are too close to the alkene moiety interfere with monolayer formation and yield disordered monolayers.

Wet chemical routes to the assembly of organic monolayers on silicon surfaces via the formation of Si–C bonds: surface preparation, passivation and functionalization

“…31 That is, the silicon-carbon bond is highly stable under a range of conditions. [31][32][33]87 We note that a major departure from the prevailing theories on the hydrosilylation mechanism has recently emerged.…”

“…[23][24][25] As comprehensively reviewed elsewhere, [26][27][28][29][30] and as discussed to an introductory level in a following section of this review (Section 2), formation of molecular layers on crystalline silicon surfaces without an intervening oxide layer is an extremely appealing approach toward robust layers on a surface. [31][32][33][34] Silicon-carbon linked monolayers on silicon substrates are expected to complement and/or extend the applications of the currently most relevant technological material 35 toward the development of atomic scale devices, [36][37][38] diverse molecular devices, [39][40][41][42][43][44][45][46][47][48] and well-defined sensing interfaces. [49][50][51][52][53] The following sections are intended as an up-to-date presentation of the topic of molecular layers on non-oxidized silicon surfaces.…”

“…221 This two-step procedure (activation followed by nucleophilic displacement) does not require harsh hydrolysis steps as in the case of tethered acid esters. 33,222 It was implemented by Wojtyk et al 223 and by Yin et al 52 through the direct thermal and photochemical (UV-mediated) attachment of N-succinimidyl undecenoate (o-NHS-functionalized 1-alkene) onto porous silicon and Si(100)-H surfaces, respectively. Furthermore, irradiation with visible light (447 nm) at room temperature of n-type Si(111)-H substrates has been recently reported to afford good quality NHS-terminated layers in a one-pot procedure.…”

Optical Characterization of Ultrasmall Si Nanoparticles Prepared through Electrochemical Dispersion of Bulk Si

“…They also have the advantage of direct compatibility with organic materials via the strong and stable Si-C bond, providing a larger degree of freedom and flexibility in possible surface passivations and functionalities. [3][4][5][6][7][40][41][42][43] For example, it was recently demonstrated that H-passivated Si-np can be directly functionalized through a Si-C linkage terminating with a carboxylic acid group toward the solvent. This modification preserves the strong PL of the Si core, adds a hydrophilic interface for stability in aqueous media, and is easily reacted with primary amines to label biomolecules, all while adding only a small amount to the overall size.…”

“…The analysis has generally focused on the source of PL and the debate between the quantum confinement (delocalized) and surface state (localized) mechanisms. Researchers studying porous Si structures, [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] for example, have attributed the PL to various sources ranging from quantum-confined nanorods and nanodots [44][45][46] to surface state silanone and siloxane groups. [47][48][49][50][51][52][53][54][55][56] For Si and Ge nanoparticles prepared through various routes such as solution-phase synthesis, [1][2][3][4][8][9] electrochemical etching, 10-13 laser ablation, 14,15 and using supercritical fluids, [16][17][18] the suggested PL sources have ranged from delocalized quantum confinement states 15 to localized SiSi surface dimer states.…”