Powerful
nanosecond-range lasers using low repetition rate
pulsed laser deposition produce numerous macroscopic size particles and droplets, which embed in thin film coatings. This problem has been addressed by lowering the
pulse energy, keeping the
laser intensity optional for
evaporation, so that significant numbers of the macroscopic particles and droplets are no longer present in the evaporated plume. The result is deposition of evaporated plume on a substrate to form thin film of very
high surface quality. Preferably, the
laser pulses have a repetition rate to produce a
continuous flow of evaporated material at the substrate. Pulse-range is typically
picosecond and
femtosecond and repetition rate kilohertz to hundreds of megahertz. The process may be carried out in the presence of a
buffer gas, which may be
inert or reactive, and the increased vapour density and therefore the
collision frequency between evaporated atoms leads to the formation of
nanostructured materials of increasing interest, because of their peculiar structural, electronic and mechanical properties. One of these is carbon nanotubes, which is a new form of carbon belonging to the
fullerene (C60) family. Carbon nanotubes are seamless, single or multishell co-axial cylindrical tubules with or without dome caps at the extremities. Typically diameters range from 1 nm to 50 nm with a length >1 mum. The
electronic structure may be either metallic or semiconducting without any change in the chemical bonding or adding of
dopant. In addition, the materials have application to a wide range of established thin film applications.