Detailed mass spectrometric studies during laser ablation of Yttrium target in high vacuum

Time-integrated and-resolved mass spectrometric investigations were carried out during the laser ablation of yttrium target in high vacuum. The main aim of these experiments was to study the implications of the target surface chemistry and of the residual gas on the deposition process quality. The effect of the laser energy density on the ionic species formation during the ablation process was investigated. It was found that at a moderate laser fluence of 4.5 J/cm2 none hydrides, oxides nor nitrides of yttrium were observed; on the contrary, at a higher laser fluence of 7.6 J/cm2, the above chemical species were observed. During and after the laser ablation process, a getter effect was observed due to the absorption of the residual gas by the Y layer deposited on the internal wall of the vacuum system. The results of these mass spectrometric analyses will be useful to improve the performances of photocathodes based on Y thin films grown by pulsed laser ablation technique.