MODELING OF A LASER PLASMA SOURCE OF AMORPHIC DIAMOND

Recently, attention has been focused upon laser plasma sources of thin-film diamond. This paper reports a model of an expanding carbon plasma ablated from graphite feedstock by a focused laser beam. The model includes as essential ingredients adiabatic cooling of plasma electrons and electron-ion recombination through both collisional and radiative processes. It is shown that, under experimental conditions that have been proven relevant for producing hard amorphic diamond films characterized by a high percentage of sp3 bonds, the plasma is composed of multiple-charged carbon ions with kinetic energies of the order of 1 keV. This ionization can readily survive plasma transport to substrates positioned a few centimetres from the graphite target.