Observation of dipolar interactions betweenPb0defects at the (111) Si/SiO2interface

Dipole-dopole (DD) interactions between ${\mathit{P}}_{\mathit{b}0}$ (Si?${\mathrm{Si}}_3$) defects at the two-dimensional (2D) (111) Si/${\mathrm{SiO}}_2$ interface are revealed by electron-spin resonance. A DD fine-structure doublet develops with increasing [${\mathit{P}}_{\mathit{b}0}$] resulting in a line shape characteristic of DD interactions within a 2D dilute spin system, for which the observations are of fundamental interest. The residual line shape, devoid of DD effects, has been deduced. It is shown that a DD line broadening previously calculated for ${\mathit{P}}_{\mathit{b}0}$ is too small, thus questioning the assumed random-distribution model.