Spatial separation of fast and slow components of pulsed laser plumes

In pulsed laser deposition (PLD) technique the generation and the deposition of particulates is an undesired effect since the fine structure of the PLD films may be destroyed by their presence. In a number of cases pulsed laser ablation takes place in two steps: (i) plasma formation: a plume consisting of hot gas and small fragments leaves the sample surface within a time interval of 0–100 ns right after the ablating laser pulse; (ii) hydrodynamic regime: large molten droplets and solid fragments explode from the sample at low speed in the 1–100 μs time domain. A simple method for spatial separation of the fast plasma part of the plume (∼103–104 m/s) from the large particles of lower speed (∼10 m/s) is investigated. Using a high speed spinning target, the angular distribution of those particles can be efficiently shifted whose ejection velocity is comparable to the speed of the target at the ablating zone. Ablation of polyethylene-glycol 1000 by an ArF excimer laser is investigated when the circumferential velocity of the target was varied between 0 and 36 m/s. It is shown that, owing to the angular deflection, the spatial displacement of the ejected particulates in the deposit increases with increasing velocity of the target, resulting in partially particulate free films.