Experimental study on droplet generation during excimer laser ablation of polyethylene glycol 1000

Abstract

Droplet generation during laser ablation is important from the point of view of the quality of films deposited by pulsed laser deposition. Dependence of the emitted droplet properties and distribution on the state of matter, viscosity and fluence was investigated experimentally. Polyethylene glycol (PEG) 1000 having relatively low melting point (37°C) was used in our experiments. By variation of target temperature between 23 and 80°C the amount and dimensions of emitted droplets were studied. An ArF excimer laser was used for irradiation, the applied fluence was varied in the range of 0.37–2.66J/cm2. The droplets were caught onto a quartz plate placed above the target. During the transition from solid to liquid state of PEG 1000 the number and the total volume of droplets emitted during ablation were drastically decreased, reaching a minimum at 40°C. Further heating of the molten target resulted in increment in the amount of emitted droplets. At 70°C target temperature the maximum quantity of droplets were deposited at a fluence of 1.28J/cm2. It was found that with increasing viscosity the number and total volume of droplets decrease significantly. Deposition with the smallest amount of droplets is reached, when using molten targets near to melting point with a high viscosity.