Carbon films with a novel sp2 network structure

TL;DR

This paper reports the synthesis of novel carbon films with a unique sp2 network structure, exhibiting high hardness and elastic recovery, characterized by advanced microscopy and spectroscopy techniques.

Contribution

It introduces a new form of carbon thin film with a fullerene-like structure and high mechanical strength, analyzed through microstructural and bonding studies.

Findings

Films have high hardness (45 GPa) and elastic recovery (85%)

Microstructure consists of curved graphene sheet segments

Mainly sp2 bonded carbon in the films

Abstract

Laser-Arc evaporation of a graphite target has been used to deposit carbon films that exhibit high hardness (45 GPa) and elastic recovery (85%). High Resolution Electron Microscopy (HREM) and Electron Energy Loss Spectroscopy (EELS) were subsequently used to study the microstructure and bonding of the resultant layers. The structure of the films from HREM is seen to consist of a dense array of parallel curved graphene sheet segments packed in various orientations. EELS reveals that the films are comprised of mainly sp2 bonded carbon. The results suggest that a new form of carbon thin film with fullerene-like structure can be realised. In order to explain how a predominantly sp2 bonded material can exhibit such a high hardness, a simple model is proposed to correlate the excellent mechanical properties with the observed structure.