High purity yttrium was ablated by using frequency quadrupled ultra-violet pulses of a Nd:YAG laser (λ=266 nm, τFWHM=7 ns) with power density of about 1 GW/cm2. Laser ablation process was studied using in-situ mass spectrometry of the ablated species in combination with ex-situ analyses of both target surface and deposited films. An increase on the Y ablation rate was found at the beginning, followed by a significant drop with increasing of the number of laser pulses per site until it reaches a constant value after 40 pulses per site. Initial topographic changes on the target surface, observed by scanning electron microscope investigations, and plasma shielding effect could be the origin of these changes on the ablation rate. Careful time-integrated and -resolved mass spectrometric studies of the laser ablated material indicate evident hydridation and oxidation processes in gas phase of ablated yttrium. These results clearly suggest that high purity metallic thin films can be deposited only after a deep and prolonged laser cleaning treatment of the target surface. The present parametric studies are aimed and tailored to prepare photocathodes based on Y thin films to be used in RF photoinjectors.
In-situ and ex-situ investigations of pulsed laser ablation of Y target
LORUSSO, ANTONELLA;PERRONE, Alessio
2011-01-01
Abstract
High purity yttrium was ablated by using frequency quadrupled ultra-violet pulses of a Nd:YAG laser (λ=266 nm, τFWHM=7 ns) with power density of about 1 GW/cm2. Laser ablation process was studied using in-situ mass spectrometry of the ablated species in combination with ex-situ analyses of both target surface and deposited films. An increase on the Y ablation rate was found at the beginning, followed by a significant drop with increasing of the number of laser pulses per site until it reaches a constant value after 40 pulses per site. Initial topographic changes on the target surface, observed by scanning electron microscope investigations, and plasma shielding effect could be the origin of these changes on the ablation rate. Careful time-integrated and -resolved mass spectrometric studies of the laser ablated material indicate evident hydridation and oxidation processes in gas phase of ablated yttrium. These results clearly suggest that high purity metallic thin films can be deposited only after a deep and prolonged laser cleaning treatment of the target surface. The present parametric studies are aimed and tailored to prepare photocathodes based on Y thin films to be used in RF photoinjectors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
