Compressive stress during continued growth

Two additional observations may provide clues as to the origin of the compressive stress. First of all, if the growth is interrupted while the stress magnitude is at its plateau value, the stress magnitude falls off rapidly. Then, upon resumption of the deposition flux, the falloff in stress magnitude is fully reversed and the same compressive stress plateau is eventually re-established (Shull and Spaepen (1996), Floro et al. (2001)). The second observation concerns the role of grain boundaries. It has been demonstrated that the stress in Pd films deposited on polycrystalline Pt substrates becomes compressive while the stress in otherwise identical films deposited onto single crystal Pt surfaces remains tensile (Ramaswamy et al. 2001). 

Presumably, the compressive stress that arises in polycrystalline films is due to an excess number of atoms comprising the film. The available 

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