Y thin films grown by pulsed laser ablation

The effects of laser fluence on the growth characteristics and surface morphology of yttrium films grown by pulsed laser deposition are investigated. The presence of droplets in the deposited films, which is the main drawback of pulsed laser deposition technique, was studied at different laser fluences. The morphology and the structure of the grown films were studied by scanning-electron microscopy and x-ray diffraction, respectively. Careful scanning-electron microscope investigations obtained by tilting the samples show that the droplets arrive to the substrate in the molten phase. The ablation rate measured at five different laser fluences (0.9–7.6 J/cm2) shows a nonlinear trend correlated with the presence of the plasma-shielding effect. The present interest in the deposition of yttrium thin films by laser ablation is due to the well-known photoemission characteristics of this metal. Depositing good-quality thin films with high adhension and low droplet density will improve the performance of photocathodes by reducing both the dark current and the thermal emittance of the photoemitted current.