Direct stress measurements in thin polymer films

Stresses in thin polymer films were quantitatively determined by measuring the deflection of a cantilever cut from a film-covered silicon nitride membrane using a focused ion beam. Spin-cast high molecular weight films showed a surprisingly high residual stress, which by far exceeded the tensile strength of the bulk polymer. Thermal annealing relaxed these stresses suggesting two relaxation mechanisms, both of which are much faster than the reptation time.