<title>Comparative study of deposition of thin films by laser-induced PVD with femtosecond and nanosecond laser pulses</title>

Sub-ps Laser Deposited Copper Films for Application in RF Guns

“…The ns ablation thresholds of copper range from 0.3 J/cm 2 [ 34 ] through 0.5 J/cm 2 [ 35 ] and 2.0–2.5 J/cm 2 [ 36 ] up to 5–6 J/cm 2 [ 35 , 37 , 38 ]. In the context of this study the most relevant figure is 3.4 ± 0.5 J/cm 2 reported for KrF excimer laser processing [ 39 , 40 ]. Since, in our case, the highest ASE fluence value of 0.037 J/cm 2 calculated for 0.30 mm 2 spot size was two orders of magnitude lower than the most relevant figure [ 39 , 40 ] and even the absolute lowest one of 0.3 J/cm 2 reported [ 34 ] is one order of magnitude higher, it is safe to say that in our experiments the ns component did not ablate.…”

“…In the context of this study the most relevant figure is 3.4 ± 0.5 J/cm 2 reported for KrF excimer laser processing [ 39 , 40 ]. Since, in our case, the highest ASE fluence value of 0.037 J/cm 2 calculated for 0.30 mm 2 spot size was two orders of magnitude lower than the most relevant figure [ 39 , 40 ] and even the absolute lowest one of 0.3 J/cm 2 reported [ 34 ] is one order of magnitude higher, it is safe to say that in our experiments the ns component did not ablate. The intensity figures in Table 1 further strengthen this statement: since below a prepulse level of 10 7 W/cm 2 , the amplified spontaneous emission of the amplifier did not cause measurable preplasma formation or photo-evaporation of the target material [ 41 ], the 4.9 × 10 6 maximum ASE intensity was definitely not enough for producing plasma components.…”

“…Therefore, the excellent agreement in the ablation thresholds reported at F th = 0.50 ± 0.05 J/cm 2 [ 42 , 43 , 44 , 45 , 46 ] is reasonable. Nevertheless, material removal at extremely low rates, slowly increasing with fluence was shown to be possible even below 0.5 J/cm 2 [ 47 , 48 , 49 ], while 0.35 and 0.15 J/cm 2 were derived as thresholds in 500 fs@248 nm PLD [ 40 , 50 ].…”

“…In order to judge the efficiency of our approach, the growth rates derived were compared to those reported in [ 40 ], actually one of the first studies performed using a 500 fs@248 nm laser. In this study, focusing the beam onto a 0.05 mm 2 spot resulted in growth rates between 2 × 10 −3 and 3 × 10 −3 nm/pulse within the 0.4–6.0 J/cm 2 fluence domain.…”

Les dépôts en couches minces par ablation laser en régime d'impulsions ultra-courtes : état de l'art et perspectives

“…Par ailleurs, l'absence (ou la reduction) de la zone fondue lors du processus d'ablation devrait eliminer (ou diminuer) le phenomene d'emission de gouttelettes liquides, responsable de la degradation des proprietes de surface des depots [9]. Les caracteristiques physico-chimiques des plasmas produits en regime femtoseconde : Taux d'ionisation, energie cinetique et masse des especes ablatees, devraient aussi influer sur le processus de croissance et la structure des films, comme le confirment les resultats des experiences realisees sur le carbone [13]. Par ailleurs, les vitesses de depot instantanees extremement elevees atteintes en regime femtoseconde, pourraient avoir des consequences sur les proprietes des couches en croissance [22].…”