Local Probe Oxidation of Self-Assembled Monolayers on Hydrogen-Terminated Silicon

Abstract

Local probe oxidation experiments by conductive AFM have been performed on a hexadecyl monolayer and a N-hydroxysuccinimide (NHS)-ester-functionalized undecyl (NHS-UA) monolayer assembled on hydrogen-terminated (i.e., unoxidized) silicon. The oxidation conditions for the mild oxidation of the top terminal groups of monolayers and the deep oxidation of the underlying silicon into silicon oxide were investigated. The results show that the bias threshold for the AFM tip-induced oxidation of the top groups of monolayers on oxide-free silicon can be reduced by 2 V for the methyl-terminated hexadecyl monolayer and even by 3.5 V for the active NHS-ester-terminated undecyl monolayer, in comparison to a methyl-terminated octadecyl trichlorosilane (OTS) monolayer on oxidized silicon. Upon such local mild oxidation, the active NHS ester group of the NHS-UA monolayer is selectively cleaved off to generate carboxyl-containing monolayer nanopatterns, opening further possibilities for subsequent patterned multifunctionalization.

Conductive AFM Patterning on Oligo(ethylene glycol)-Terminated Alkyl Monolayers on Silicon Substrates: Proposed Mechanism and Fabrication of Avidin Patterns

“…18,22,3537 Here, we propose that, in addition to hydroxyl radicals, the local probe oxidation may also be initiated by hydrogen radicals generated in the system. There are five routes to generate hydroxyl radicals and hydrogen radicals (eqs (1)–(5), Figure 5).…”

“…18,22,35–37 Here, we propose a mechanism for the process in general and the possible products generated on OEG-alkyl monolayers on silicon.…”

Silicon and Silicon-Related Surfaces for Biosensor Applications

“…In addition, micro-contact printing (μCP) -a fast and simple patterning technique, which is frequently used for alkylthiols on gold and alkylsilanes on oxide surfaces [Xia & Whitesides, 1998] -is currently not feasible with 1-alkenes and 1-alkynes directly on H-Si, due to the extended reaction times required for monolayer formation and related difficulties to remain a oxide-free monolayer-silicon interface. Only recently a number of elegant soft lithographic [Jun, et al, 2002& Mizuno & Buriak, 2008& Perring, et al, 2007 and scanning probe [Niederhauser, et al, 2001& Niederhauser, et al, 2002& Yang, L., et al, 2005& Yang, M., et al, 2009] methods for patterning of organic monolayer on oxide-free silicon were published.…”

Selective surface modification of lithographic silicon oxide nanostructures by organofunctional silanes

“…In general, the different binding mechanisms that can be used for the selective functionalization of local anodic oxidation patterns on monolayer-terminated silicon can be divided into three major groups: (A) intermolecular interactions [10–11], (B) electrostatic/ionic interactions [12–13], and (C) covalent bonds [14–17]. Covalent attachment of molecules is thereby a most favorable method since covalent bonds possess comparable high dissociation energy (several 100 kJ/mol), and with the knowledge of their successful implementation on nanostructures, the whole realm of modular chemistry can be applied (e.g., “Click”-chemistry [18]).…”