Rare earth effect on laser produced plasma dynamics during pulsed laser deposition of doped cobalt ferrite

Abstract

The addition of rare earth elements the ferrites can lead to significant changes in structural, magnetic and electric properties of bulk materials and also of thin films deposited by pulsed laser deposition. The present study relies on the analysis of the laser induced plasma of three sets of cobalt ferrite targets doped with various concentrations of RE elements (Dy, Gd, Yb) and proposes a correlation of the derived results with structural investigations of the films obtained during the same experiment. ICCD imaging and space-and time-resolved optical emission spectroscopy techniques were used to obtain information on the dynamics and excitation temperatures of various species found in the laser produced plasmas (LPP). Initial investigations on the global behavior of the LPP revealed that the addition of RE reduced the drift velocities of the formed plasma structures, the lowest ones being observed for the targets doped with the heaviest RE (Yb). Space-and time-resolved spectroscopy measurements applied for all main elements (Fe, Co and RE - both neutral and ionic species) showed a complex dynamic system, with decreased/increased kinetic energies for neutrals/ions at high dopant concentrations, suggesting a possible re-sputtering effect at the films surface. The individual excitation temperatures of the main elements derived from Boltzmann plots increased as the RE content was augmented via radiative collision events due to their larger diameters compared with Co, Fe or O. The spatial distribution of electron temperature can be explained by the charge separation occurring with the addition of RE in the investigated systems.