Threshold and efficiency for perforation of 1 nm thick carbon nanomembranes with slow highly charged ions

Abstract

Cross-linking of a self-assembled monolayer of 1,1'-biphenyl-4-thiol by low energy electron irradiation leads to the formation of a carbon nanomembrane, which is only 1 nm thick. Here we study the perforation of these freestanding membranes by slow highly charged ion irradiation with respect to the pore formation yield. It is found that a threshold in potential energy of the highly charged ions of about 10 keV must be exceeded in order to form round pores with tunable diameters in the range of 5-15 nm. Above this energy threshold the efficiency for a single ion to form a pore increases from 70% to nearly 100% with increasing charge state. These findings are verified by two independent methods, namely the analysis of individual membranes stacked together during irradiation and the detailed analysis of exit charge state spectra utilizing an electrostatic analyzer.

Selective ion sieving through arrays of sub-nanometer nanopores in chemically tunable 2D carbon membranes

“…In an earlier study, TEM has been used to resolve BPT-CNM membrane based pores of several nanometers in diameter, which were induced by ion beam exposure, and did not reveal any pores with smaller sizes. 32 On the other hand, we show here that pores are in fact present in the pristine BPT-CNM, as evident from transmembrane ion conductivity through the BPT-CNM membrane. The number and size of pores in a well-defined area of the membrane are determined using the ion flow through the membrane.…”

Ultrafast electronic response of graphene to a strong and localized electric field

“…No rupture could be detected. This is in strong contrast to ultrathin polymeric carbon nanomembranes, where, because of low electron mobility, creation of pores with diameters of up to a few nanometre was observed after exposure to HCIs3540. The absence of any traces of large-scale lattice deformations thus confirms the intrinsic ability of suspended SLG to locally sustain exceptionally high current densities, even though it cannot efficiently diffuse heat to a substrate910.…”

“…Failure to sufficiently resupply the lost charge and to dissipate the absorbed energy on a timescale small compared with lattice vibrations would result in Coulomb explosion tearing large holes (of the order of 10 nm) into the SLG, as we have observed for carbon nanomembranes3540. Despite the possible self-healing of localized defects in graphene41, such extended structural modifications should be detectable using transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM), yet careful investigation of the irradiated SLG does not reveal any nanometre-sized defect structures.…”

“…To extract the abundances and widths of every single peak, the spectra have to be deconvoluted with the analyser function, since the spectra are broadened by the design of the electrostatic analyser (details on the data evaluation can be found in ref. 35). The corrected abundances follow a symmetric Gaussian function with a full width at half maximum of three to five electrons as a result of final de-excitation processes.…”

A setup for transmission measurements of low energy multiply charged ions through free-standing few atomic layer films

“…One possibility to tailor 2D materials and thin films is by irradiation with ions in high charge states (HCI) [8][9][10][11]. For modelling of HCI induced damage, data on the energy deposition of the ions inside the target and the dissipation channels is indispensable [12].…”