Reflection high energy electron diffraction (RHEED) intensity measurements reveal that the strain in a Si1−xGexlayer on a vicinal Si(001) surface converts a (1×2) domain dominated step configuration to a (2×1) domain dominated one. The dependence of the effect on the Ge content is similar to the dependence of the critical thickness of the pseudomorphic growth of Si1−xGexlayers on Ge content. No conversion effect has been observed on exact Si(001) substrates. ©1996 American Institute of Physics.