engleski

Absorption study of double-pulse ablation of titanium

Dual-laser ablation has important applications for thin-film deposition or production of nanoparticles. However, details of dual-laser ablation processes and plume dynamics are still not completely understood. We performed study of titanium plume dynamics in respect to neutral particle content, in vacuum and in the presence of buffer gas, by using an optical emission spectroscopy and absorption cavity ring-down spectroscopy. Laser ablation was performed within the vacuum chamber which could be evacuated by means of a roots pump system. For ablation, in the parallel laser beam configuration, we have used two ns Q-switched Nd-YAG lasers (Brilliant 350 mJ at 1064 nm and Brio 100 mJ at 1064 nm). Laser pulses were triggered and synchronized by means of a digital delay generator. For CRDS we have used an excimer (LPX 105E Lambda Physik) pumped dye laser (LPD 3002E Lambda Physik) working with a Rhodamine B dye. The dye laser pulse duration was about 15 ns and bandwidth about 6 GHz. Targets were mounted on an X-Y translation stage to allow precise positioning and were also rotated to avoid drilling. Both target and the focusing lens could be moved by step motors. Lasers, digital delay generator, oscilloscope and step motors were controlled by a PC computer using a homemade LabVIEW program which also allows analyses of CRDS ringdown signal in various time windows. The CRDS technique was used for study of dynamics of the plume depending on the time delay between laser pulses and the buffer gas environment. Results show tenfold increase of atomic absorptions for the case of dual-laser ablation compared to single laser absorptions as well as significant horizontal spreading of the plume. Differences between emission and absorption appearances for vacuum and buffer gas presence are discussed.

dual-laser ablation; cavity ring-down spectroscopy; titanium

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