Covalently Attached Organic Monolayers onto Silicon Carbide from 1-Alkynes: Molecular Structure and Tribological Properties

Abstract

In order to achieve improved tribological and wear properties at semiconductor interfaces, we have investigated the thermal grafting of both alkylated and fluorine-containing ((C(x)F(2x+1))-(CH2)n-) 1-alkynes and 1-alkenes onto silicon carbide (SiC). The resulting monolayers display static water contact angles up to 120°. The chemical composition of the covalently bound monolayers was studied by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. These techniques indicate the presence of acetal groups at the organic-inorganic interface of alkyne-modified SiC surfaces. The tribological properties of the resulting organic monolayers with fluorinated or nonfluorinated end groups were explored using atomic force microscopy (AFM). It was found that the fluorinated monolayers exhibit a significant reduction of adhesion forces, friction forces, and wear resistance compared with non-fluorinated molecular coatings and especially bare SiC substrates. The successful combination of hydrophobicity and excellent tribological properties makes these strongly bound, fluorinated monolayers promising candidates for application as a thin film coating in high-performance microelectronic devices.

Organic Monolayers from 1-Alkynes Covalently Attached to Chromium Nitride: Alkyl and Fluoroalkyl Termination

“…19 On such surfaces, the surface properties (wettability and surface dipole/band bending) can be tuned in great detail via modification of the top group. For example, the replacement of the terminal −CH 3 with a −CF 3 group strongly diminishes the adhesion and friction forces on hydroxyl-terminated SiC, 19 analogous to observations made for fluorinated monolayers on Si.…”

Self-assembled monolayers of perfluoroalkylsilane on plasma-hydroxylated silicon substrates

“…3C, upon been treated under high temperature, the antisymmetric and symmetric methylene stretching frequencies of the SAMs shift from 2939.4 to 2937.0 cm −1 and from 2882.7 to 2879.5 cm −1 , respectively. The characteristics shift to lower wavenumbers of the antisymmetric and symmetric CH 2 stretching vibrations after heat treatment revealed a high degree of short-range ordering of the monolayers, which confirmed the reorientation of fluorocarbon chains and the formation of the ordered SAMs [36,43]. The ATR-IR results indicated that the fluoroalkylsilane monomers have assembled onto the silicon substrate surface via Si-O-Si bonds successfully, and the SAMs tend to reorient to obtain ordered monolayers after heat treatment.…”

“…Thus, various structures of monolayers consisting of perfluoroalkylsilanes have been developed to obtain lower surface energy layers or coatings. In contrast to the disorder fluorocarbon layers, a number of ordered perfluorinated monolayers with lower surface energy have been reported [35][36][37]. Two approaches can be adopted in order to reduce the surface energy of fluorinated silane assembled monolayers: One is to optimize the reaction conditions to fabricate ordered and uniform monolayers, which can avoid the side reaction during the assembly process.…”

Unsymmetrical Spiroalkanedithiols Having Mixed Fluorinated and Alkyl Tailgroups of Varying Length: Film Structure and Interfacial Properties

“…In particular, alkanethiolate-based monolayers on gold substrates are the most studied system due to their reproducible ordered structures and relatively simple preparation procedures [22,23]. The interfacial properties of the organic surfaces such as wettability [24,25], adhesion [26][27][28][29], and friction [30][31][32][33][34][35][36] can be controlled by varying the structure of the adsorbate employed.…”