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

Abstract

A low-temperature, high-energy (50keV) electron diffraction study of size-dependent structures and growth mechanisms of neon samples in multiporous “amorphous” carbon films is presented. Electron diffractograms are analyzed on the basis of the assumption that there exists a cluster size distribution in deposits formed in the substrate, and multi-shell structures such as icosahedra, decahedra, and fcc and hcp clusters are probed for different sizes up to approximately 3×104 atoms. The analysis is based on a comparison of precise experimental and calculated diffracted intensities with the help of a minimization procedure for the reliability factor R. Highly reproducible discrete distribution functions of sizes and structures are found. The time-dependent evolution of diffractograms at earlier stages of growth is revealed. Initially distinct diffraction peaks gradually “disappear,” although the total electron beam absorption attests that the deposited neon is preserved in the porous substrate. We ascribe this effect to diffusion-like gas penetration from larger to smaller pores, which results in a highly dispersed or even disordered substance. Evidently, the clusters that grow initially during deposition are later soaked up by a sponge-like substrate due to capillary forces.