Direct determination of the interaction between vacancies on InP(110) surfaces.

The interaction potential between charged P vacancies on InP(110) surfaces is determined from scanning tunneling microscopy measurements of their correlation. It is found to have a functional form of a screened Coulomb potential except at very short distances. A vacancy charge of $+1e$ is derived from the measurements. The maximum repulsion is 65 meV and the range is 3 nm.