Adatoms and their relation to surface stress

Experimental techniques are now available to measure changes in surface stress due to submonolayer coverages of adatoms on a substrate. It has been observed that even for fairly low coverage, a significant stress develops that can greatly impact growth mechanisms and defect formation during the early stages of crystal growth. In this manuscript, the relationship between adatoms and macroscopic stress is developed within a rigorous continuum framework that has direct links with atomic scale properties of adatoms. The result provides a means for measuring properties of individual adatoms and gives new insight to adatom interactions. Comparison with experiments shows that adatom interactions depend on strain. A strong strain dependence is evident, even when adatoms are far apart. It is found that the dipole characterizing an adatom may change with applied strain, strain induced by other defects, and interactions with boundaries. The analysis yields a simple relation between surface stress and the level of adatom coverage during deposition that is in agreement with experimental observations.