Low-energy electron irradiation induced synthesis of molecular nanosheets: An influence of the electron beam energy
Low-energy electron irradiation induced synthesis of molecular nanosheets: An influence of the electron beam energy
Neumann, C.; Wilhelm, R. A.; Küllmer, M.; Turchanin, A.
Aromatic self-assembled monolayers (SAMs) can be cross-linked into molecular nanosheets carbon nanomembranes (CNMs) via low-energy electron irradiation. Due to their favorable mechanical stability and tunable functional properties, they possess a high potential for various applications including nanosensors, separation membrane for osmosis or energy conversion devices. Despite this potential, the mechanistic details of the electron irradiation induced cross-linking process still need to be understood in more detail. Here we studied the cross-linking of 4'-nitro-1,1 ́-biphenyl-4-thiol SAM on gold. The SAM samples were irradiated with different electron energies ranging from 2.5 to 100 eV in ultra-high vacuum and subsequently analysed by complementary techniques. We present results obtained via spectroscopy and microscopy characterization by high-resolution X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction with micrometre sized electron beams (LEED) and low-energy electron microscopy (LEEM). To demostrate the formation of CNMs, the formed two-dimensional molecular materials were transferred onto grids and oxidized wafer and analyzed by optical, scanning electron (SEM) and atomic force microscopy (AFM). We found a strong energy dependence for the cross section for the cross-linking process, which rates decrease exponentially towards lower electron energies by about four orders of magnitude. We conduct a comparative analysis of the cross sections for the C-H bond scission via electron impact ionization and dissociative electron attachment and find out that these different ionization mechnisms are responsible for the variation of the cross-linking cross section with electron energy.
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 29910) publication
-
Faraday Discussions 227(2021), 61-79
Online First (2019) DOI: 10.1039/C9FD00119K
Cited 19 times in Scopus
Downloads
- Final Draft PDF 5,6 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-29910
Publ.-Id: 29910