Role of temporal delay in dual-laser ablated plumes

A novel laser ablation process using two lasers of different wavelengths has demonstrated the capacity to grow essentially particulate-free thin films without compromising the ionic excitation and kinetic energy of the plume species. We demonstrate in this article, the critical role of the interpulse delay when a pulsed CO2 laser spatially overlaps an excimer (KrF) laser on the ablation target during this dual-laser ablation process. At the optimum delay, the excitation and the ionization of the plume were significantly enhanced. The time-of-flight ion probe studies indicate more than a fourfold increase in the ion kinetic energies for this optimized process in comparison to the single-laser ablated plumes. The choice of a suitable delay also facilitates an optimization of elimination of particulate ejection that is typical of single-laser ablation. The morphology of the dual-laser ablated Er-doped Y2O3 films deposited on Si substrates as a function of interpulse delay is also discussed.