INFLUENCE OF PLD AND CVD EXPERIMENTAL GROWTH CONDITIONS ON CARBON FILM NANO- STRUCTURE EVOLUTION

摘要

Owing to their outstanding properties, many research efforts have been focused on the growth and application of carbon based materials, mainly single or multi-wall carbon nano-tubes, nano-horns and cones, fibres . Nano-structured carbon films have also been proved to be a very promising field emitting material, providing the nano-graphene structure have the constituting basal plane oriented perpendicular to the substrate. Pulsed Laser Deposition (PLD) and Chemical Vapour Deposition (CVD) methods have been used to prepare carbon films of different nano-structure ranging from amorphous carbon to nano-clustered graphite and nano-wires. The influence of experimental conditions (v.z. deposition system and parent species, substrate heating, working pressure, inert sustaining gases, RF or DC plasma assisted deposition) on the carbon atom clustering, particle aggregation and structure evolution has been thoroughly analysed. Nd:YAG pulsed laser ablation of a graphite target produced nano-structured films when assisted by plasma or at high substrate temperature. Hot Filament CVD was able to grow nano-graphite "petal"-like structures vertically oriented at moderate substrate temperature ( 650℃) and sharp graphite tips and cones at high T (1650 ℃). The presence of a DC plasma was able to produce big "urchin" structures characterised by long, entangled, tubular wires (stripes), without any catalyst addition. The film morphology have been characterised by SEM; film quality and nano-particle dimension have been estimated be Raman spectroscopy. Field emission properties have been measured by a planar / spherical configuration.