Interaction between a laser produced plasma and a solid substrate, in a low pressure neutral background gas

Summary form only given. Pulsed laser deposition (PLD) of thin films has evolved into a well established technique. In the particular case of thin carbon films, it has been found to be suitable to grow carbon nanotubes, graphene and diamond like carbon (DLC) amongst others. Previously we have investigated PLD of thin carbon films using a graphite target, in low pressure Argon gas background. Raman spectroscopy based structural analysis of the films showed a correlation between films properties and pressure of the buffer gas background. In order to better understand the deposition process, we have studied in detail the dynamics of the laser carbon plasma close to the substrate where the carbon film grows. An Nd:YAG laser pulse, 370 mJ, 3.5 ns, at 1.0 6 μm, at 6.7 J/cm² fluence, is used to produce a carbon plasma from a solid graphite target, in different neutral background gases, Argon, Helium and Nitrogen, at pressures below 1.5 Torr. Observations of the dynamics of the laser produced plasma, using time resolved plasma imaging, filtered with 10 nm windows at characteristic carbon species emission wavelengths, show multiple fronts of the expanding plasma, with different species composition, carbon ions and carbon molecules. When the substrate is located at 20 mm from the graphite target, we observed that a C₂ rich plasma strikes the substrate and bounces, stagnating closer to the substrate for several microseconds. Besides a general characterization of the plasma dynamics close to the substrate, we will present time and space resolved optical omission spectroscopy observations, recorded with 15 ns time resolution and ~3 mm spatial resolution, at different stages of the carbon film growth process.