Carbon films with an sp2 network structure

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 sheetsegments packed in various orientations. EELS reveals that the films are comprised of mainly sp2 -bonded carbon. The results suggest that a form of carbon thin film with fullerenelike structure can be realized. In orderto explain how a predominantly sp2 -bonded material can exhibit such a highhardness, a simple model is proposed to correlate the excellent mechanical properties with the observed structure.