Neon in carbon nanopores: wetting, growth mechanisms, and cluster structures

Abstract

Low-temperature high-energy (50 keV) electron diffraction study of size-dependent structures and growth mechanisms of neon samples in multiporous «amorphous» carbon films is presented. Electron diffractograms were analyzed on the basis of the assumption that there exists the cluster size distribution in deposits formed in substrate and multi-shell structures such as icosahedra, decahedra, fcc and hcp were probed for different sizes up to approximately 3·10 4 atoms. The analysis was based on the comparison of precise experimental and calculated diffracted intensities with the help of the R (reliability) -factor minimization procedure. Highly reproducible discrete distribution functions of sizes and structures were found. The time-dependent evolution of diffractograms at earlier stages of growth was revealed. Initially distinct diffraction peaks gradually «disappeared» although the total electron beam absorption evidenced that deposited neon was preserved in the porous substrate. We ascribed this effect to diffusion-like gas penetration from larger to smaller pores which resulted in a highly dispersed or even disordered substance. Evidently, clusters initially grown during deposition were later soaked by a sponge-like substrate due to capillary forces.

Evidence for high saturation of porous amorphous carbon films by noble gases

“…Thus, large clusters form in the essentially open geometry, which explains the wide application of these so-called «amorphous» carbon films in the electron microscopy and the electron diffraction as supporting substrates. But it was shown also, and has been confirmed in our previous studies [6,[18][19][20][21][22] that carbon films prepared by means of vacuum sublimation of graphite can be characterized as a porous matrix with very fine channels. This finding correlates with the essentially damped atomic dynamics in neon clusters formed in pores [19], which is ascribed to strong interaction of neon atoms with carbon walls.…”

“…Diffractograms were analyzed applying the simulations which were similar to those described previously [6,[17][18][19][20][21][22], i.e. basing on the assumption of a wide variety of possible structures and sizes involved in the formation of observed diffraction patterns.…”