Density of ultra-thin graphite films

Abstract

Density (ρ) of ultra-thin graphite films whose thickness are 41 - 300 nm was experimentally determined by a sink-floating method using solvents of acetone and diiodomethane. The films were synthesized from the heat treatment of spin-coated benzimidazobenzophenanthroline ladder (BBL) polymer films. The measured ρ of the films decreased as the thickness become thinner, and the thinnest film of 41-nm thick takes the lowest ρ of 1.76 ± 0.01 g/cm³. From the characterization of the films by the X-ray absorption near-edge structure (XANES) measurements in the CK region, it can be clarified that the films are surely graphite and their orientation of the graphitic structure is much disordered as the thickness becomes thinner. It is therefore considered that thinner graphitic films with the several tens–hundreds nm thick take lower ρ due to the much-disordered graphitic local structures.