  Conventional polycrystalline materials acquire high levels of intrinsic
mechanical stress (ranging from MPa to a few GPa) during preparation and use,
but this stress decays quickly (~minutes) to small residual values (~kPa) under
standard resting conditions. Nanocrystalline materials reach similar or even
higher levels of intrinsic stress, but surprisingly retain a significant
portion of this stress over much longer time scales (~hours). This behavior
directly contradicts current theoretical models that predict stress relaxation
through diffusive currents. Diffusive currents, which flow mainly on the
surfaces of grains, are expected to produce faster relaxation kinetics when the
stress to be released is higher. In this work, we study the kinetics of
intrinsic stress relaxation in nanocrystalline films and identify the
limitations of this process as a preliminary step towards designing a strategy
for high-stress stabilization in nanostructured systems.
