Role of the step density in reflection high-energy electron diffraction: Questioning the step density model

The step density model of reflection high-energy electron diffraction oscillations is investigated. Within this model, the temporal evolution of the specular beam intensity during growth by molecular beam epitaxy represents the evolution of the step density during deposition. This is found to be inconsistent with diffraction theory. In particular, when the concentration of atoms in the deposited layer is fixed, an increase of the step density causes an increase of the specular beam reflectivity, contrary to the prediction of the step density model.