Surface thermal fluctuation spectroscopy study of ultra-thin ionic liquid films on quartz

We apply a surface thermal fluctuation spectroscopy technique to investigate the liquid nature of ionic liquid (IL) thin films and micro-droplets. While the spectrum for bulk IL was well explained by a simple Newtonian fluid model, a significant contribution of viscoelasticity was suggested for the vacuum-deposited thin films and micro-droplets. For a sample of IL micro-droplets with statistical distributions of their size and thickness, the scanning surface fluctuation spectroscopy was demonstrated to spatially map out the thickness and viscoelasticity values for effectively investigating the correlation between them, successfully reproducing a typical surface morphology of the sample as well.