Adatoms and their relation to surface stress

Surface stress generation during formation of alkanethiol self-assembled monolayer (SAM)

“…Following Kukta et al (2003), the elastic field induced by an adsorbed alkanethiol molecule is approximated by a force dipole acting on the surface. Strength of the adsorbed molecules induced force dipole is expressed as function of surface strain and adsorbed molecules interact with each other through their elastic fields.…”

On the dependence of adatom interactions on strain

“…(2.17) and (2.18). A more general surface phase is treated in Kukta et al (2003) where a static analysis is used to calculate the elastic ÿeld of an adatom. where the ÿrst two terms comprise the total internal energy and the last term is the work done by the applied traction T i .…”

“…For an isotropic surface and a linearly elastic adatom phase, adatom energy is written as I ( fp;I ) = I 0 + D I fp;I + F I fp;I where I 0 ; D I ; F I and H I are constants that depend on adatom species and the substrate material and surface orientation. A method of evaluating these constants from an atomistic model is discussed in Kukta et al (2003). However as mentioned earlier, they are perhaps best determined from measurements of surface stress versus adatom coverage.…”

“…Measurements of surface stress versus adatom density can be used to determine constitutive constants related to the dependence of adatom interactions and adatom dipoles on strain. Kukta et al (2003) discuss this and present a simple relationship between surface stress and the dipole of an adatom in two-dimensions where an "adatom" is actually a string of atoms, unbounded in one direction. The three-dimensional result, which is needed for direct contact with experiment, will be presented in a future publication.…”

“…This issue is best resolved by determining adatom properties from physical measurements of surface stress. Atomistic calculations can be used to evaluate adatom properties (Kukta et al, 2003), but it is not clear that available interatomic potentials will accurately capture the strain dependence. The properties of an adatom depend on its species and also on its substrate.…”