Odd?even effect in electron beam irradiation of hybrid aromatic? aliphatic self-assembled monolayers of fatty acid

Abstract

Electron irradiation of aromatic self-assembled monolayers (SAMs) in combination with different lithographic approaches provides an interesting alternative for high-resolution surface patterning. More recently, it has been also demonstrated that this process can be used for carbon nanomembrane (CNM) fabrication, which forms technologically attractive 2D materials, with potential applications in different areas of nanotechnology such as ultrafiltration and nanobiosensing. To better understand the relation between the original SAM structure and the resulting CNM formation, in the current study, we conduct systematic analysis of the electron irradiation process for a model SAM system deposited on Ag substrates and based on a homologue series of biphenyl substituted carboxylic acids [C6H5?C6H4?(CH2)n?COO/Ag, n = 2?6] with different lengths of the aliphatic linker defined by the number n. Our results of X-ray photoelectron spectroscopy of irradiated monolayers show that the process of electron-induced desorption, cross-linking, and elimination of the SAM binding group depend on the parity of the parameter n (the odd?even effect). Our observations indicate a way for controlling thickness and purity of such nanomembranes, which are the key parameters determining the range of CNM applications.