In situ observation of surface deformation of polymer films by atomic force microscopy

The tensile X-Y stage, providing a load cell and a stretching device, has b een constructed to observe the surface deformation of polymer film in situ by using an atomic force microscope (AFM). From the three-dimensional AFM i mages, the streak-like bumps were observed on a polyethylene terephalate (P ET) film surface. By monitoring the change in the distance between them by the tensile load, the strain was evaluated in the direction both parallel a nd perpendicular to the tensile direction. The microscopic stress-strain re lationship by AFM coincided with the macroscopic one, which indicates so-ca lled affine deformation of PET film. Young's modulus was obtained as 2.3 GP a for PET from the initial slope of the stress-strain curve by AFM. The app arent Poisson ratio of the PET film surface could be also evaluated. (C) 20 00 American Institute of Physics. [S0034-6748(00)01605-1].