Impact of negative line tension on the shape of nanometer-size sessile droplets.

The sign and value of the line tension has been measured from the size dependence of the contact angle of nanometer-size sessile fullerene (C60) droplets on the planar SiO2 interface, measured with atomic force microscopy (AFM). Analysis according to the modified Young's equation indicates a negative line tension, with a magnitude between -10{-11} and -10{-10}  N/m, in good agreement with theoretical predictions. The experiments also indicate that droplets with contact area radii below 10 nm are in fact two-dimensional round terraces.