Grafting and Polymer Formation on Silicon from Unsaturated Grignards:  II. Aliphatic Precursors

Abstract

Anodic decomposition of a vinylmagnesium halide or an ethynylmagnesium halide at a surface-hydrogenated silicon electrode leads to the formation of polymeric layers covalently anchored to the silicon surface. These layers have been characterized using spectroellipsometry and photoluminescence, infrared, and X-ray photoelectron spectroscopy. In the case of vinyl precursors, it appears that the multiple bonds are largely broken in the process. In the case of ethynyl, the layer formation rate is much higher for the chloride than for the bromide. The obtained polymer appears as a saturated skeleton bearing halide and unsaturated ethynyl groups. Furthermore, it appears that the solvent may be attacked by the ethynyl radicals leading to contamination of the polymer by solvent fragments, an effect that can largely be avoided by using appropriate solvents. The reaction pathways are discussed.

Electrografting: a powerful method for surface modification

“…Anodic electrografting of Grignard reagents (RMgX) has been investigated on Si, an easily oxidized substrate, but the experiments were performed in extra dry (Grignard reagents are intrinsically dry as they react immediately with traces of water) and oxygen-free conditions to avoid the oxidation of Si to SiO 2 . [101][102][103][104][105][106][107] Photoanodic grafting has been performed to obtain patterned surface by use of a mask. 108 Thermal grafting is also possible with Grignard reagents but the layers are of lower quality.…”

“…It should noted that the solutions are highly resistive, precluding any electrochemical investigation. SiH surfaces have been modified with methyl, 102,111 alkyl, 103,108,111,112 aryl, 106 or vinyl and ethynyl 107,113 Grignard reagents. The modified surfaces have been characterised by IR as Si itself can be used as an ATR (Attenuated Total Reflectance) prism.…”

“…This confirms that the solvent is involved in these electrografting reactions. 103,106,107 This internal reflection ATR method permits the in situ the grafting process to be followed. For example, during the electrografting of decylmagnesium bromide, the SiH band decreases while the signals corresponding to the decyl group increase.…”

Multi‐instrument characterization of the surfaces and materials in microfabricated, carbon nanotube‐templated thin layer chromatography plates. An analogy to ‘The Blind Men and the Elephant’

“…Clearly, many researchers recognize the importance of employing multiple analytical techniques to characterize surfaces and materials . However, to better understand the degree to which this message is being put into practice, we selected 13 papers from nine research groups on the topic of surface modification of hydrogen‐terminated, porous, and scribed silicon with carbon–carbon double bond containing reagents . This is an area in which one of us (MRL) has published .…”

(Allesandro Volta Award Presentation) Facts and Challenges in the Electrochemistry and Wet Surface Chemistry of Silicon

“…In the context of the development of high-K oxide technology for next-generation MOSFETs, the unique thermal stability of the methylated Si surface has been proposed as a method to avoid formation of an interfacial SiO2 layer during MOCVD deposition of HfO2 on silicon (153). Aromatic or unsaturated groups (vinyl, ethynyl) can also be grafted from Grignard precursors (154,155). However, in that case the aryl, enyl or ynyl radical formed is able to abstract hydrogen from most solvents and to undergo reactions with the already grafted groups.…”