Time-resolved spatial distribution of plasma in the ablation of a Ba0.6Sr0.4TiO3 target by 25 ns KrF ultraviolet laser

We performed radially and longitudinally time-resolved plasma analysis during pulsed laser deposition of Ba_0.6Sr_0.4TiO₃ thin films. The plasma is shown to be optically thick and strongly non-uniform during the early expansion phase and the resonance line Ba II (455.4 nm) is strongly self-reversed during this time. Plasma temperature and electron density were obtained by comparing experimental emission spectra with the spectral radiance computed for a non-uniform plasma in local thermal equilibrium.