FRACTURED POLYMER SILICA FIBER SURFACE STUDIED BY TAPPING MODE ATOMIC-FORCE MICROSCOPY

A silica optical fiber was imaged using an atomic force microscope (AFM) in both contact and tapping mode. The fiber surface contains fragments of tow-modulus, viscoelastic polymer after the coating was mechanically removed. While scanning in the contact mode resulted in tip-induced irreversible damage of the polymer, the tapping mode AFM generated reproducible images of the surface topography. It is shown that tapping mode AFM can reduce the contact force significantly, estimated to be as low as a tenth of a nanonewton, even in ambient conditions. This is facilitated by oscillating the tip (i.e. the cantilever) in the vicinity of the surface with an amplitude of up to approximately 100 nm, which would eliminate capture of the tip by the surface fluid layer. Since the tip is no longer continuously in contact with the surface, both tip and sample degradations are minimized. The example presented herein demonstrates the utility of the tapping mode AFM; evidence is provided which supports the proposed bonding mechanism at the polymer/silica interface.