Ion-sculpting of nanopores in amorphous metals, semiconductors, and insulators

Abstract

We report the closure of nanopores to single-digit nanometer dimensions by ion sculpting in a range of amorphous materials including insulators (SiO2 and SiN), semiconductors (a-Si), and metallic glasses (Pd80Si20)—the building blocks of a single-digit nanometer electronic device. Ion irradiation of nanopores in crystalline materials (Pt and Ag) does not cause nanopore closure. Ion irradiation of c-Si pores below 100 °C and above 600 °C, straddling the amorphous-crystalline dynamic transition temperature, yields closure at the lower temperature but no mass transport at the higher temperature. Ion beam nanosculpting appears to be restricted to materials that either are or become amorphous during ion irradiation.

Structural and chemical evolution of Au-silica core–shell nanoparticles during 20 keV helium ion irradiation: a comparison between experiment and simulation

“…The second mechanism would be excitation of individual atoms into excited surface states , which can then diffuse across the 'cold' surface, coming to rest www.nature.com/scientificreports/ at the connection between the particle and substrate. Both of these mechanisms have been considered before in ion sculpting experiments 52,53 .Our data are insufficient to choose one or the other, so we present these possible mechanisms and leave the question of which is occurring for future projects.…”

Thermal activation and saturation of ion beam sculpting

“…Fabrication details for all samples are provided elsewhere. 5 The ion sculpting apparatus has been described in detail elsewhere; 1,7 the Kaufmann-source Ar þ ion beam is operated at 3 keV in continuous mode at normal incidence. With differentially-pumped argon flowing into the ion gun chamber at 1.5 Â 10 À6 Torr, the sample chamber base pressure is less than 10 À7 Torr.…”

“…Only amorphous materials, or materials that become amorphous under irradiation, exhibit nanopore closure. 5 Moreover, the closing rate of a nanopore displays a "memory effect" wherein it depends not only on the pore's instantaneous size, but also on its initial size. 6 These observations are better explained by another hypothesized mechanism: 1,6 the creation by the ion beam of a very thin, stressed viscous surface layer, where compressive stress caused by the ion beam is relieved; viscous flow of the thin surface layer with a viscosity reduced by ion irradiation acts to close the pore.…”

Controllable shrinking of inverted-pyramid silicon nanopore arrays by dry-oxygen oxidation

“…Solid-state nanopores and nanopore arrays have attracted considerable research interest due to their potential applications in many fields, such as near field optics [1] and nanostructure fabrication [2], and in particular as biosensors for single molecule analysis of DNA and proteins [3][4][5][6]. Over the years, there have been many techniques to fabricate solid-state nanopores, such as direct electron beam drilling [7][8][9] and ion beam drilling [10][11][12], as well as indirect nanopore shrinking [13,14] and sculpting processes [15,16] based on prefabricated pores. With such techniques, nanopores with diameters of several nanometers have been obtained.…”