Labyrinthine and dendritic patterns in polyethylene oxide films grown by pulsed laser deposition

Polyethylene oxide (PEO) films were grown by pulsed laser deposition using two different lasers: ArF (193 nm, 5 ns) and Nd:YAG (355 nm, 7 ns). Even though very similar experimental conditions have been applied to ablate identical targets, different surface morphologies and structures have been observed. Depending on laser fluence, labyrinthine patterns in PEO films have been formed when using 355 nm laser pulses at fluence values in the range 280–1000 mJ/cm2. The same material ablated by 193 nm excimer laser pulses at 200 mJ/cm2 fluence grows in dendritic morphologies. Both target and laser deposited materials have been thoroughly characterized using infrared spectroscopic, microscopic and X-ray analytical methods. Infrared spectroscopy demonstrated the close similarity of molecular chains for both target and film materials. X-ray diffraction analysis indicates polymer chain scissoring by ultraviolet irradiation, a fact also confirmed by size exclusion chromatography.