Imaging subsurface strain at atomic steps on Si(111)

Using diffraction contrast in a transmission electron microscope, we show that the subsurface strain around a monatomic step can be revealed on Si(111). The strain appears because small associated lattice plane rotations change the Bragg conditions locally. By image matching with models of the strain field, we are able to identify the magnitude of the strain at the step. While monolayer steps at surfaces have been previously observed, weak beam images reveal contrast which allows for the direct analysis of the associated strain.