Step-step interactions on the vicinal Ge(001) surface

Ge(001) surfaces misoriented towards the [011] direction have been investigated with a UHV STM. The vicinal Ge(001) surface consists of alternating straight SA steps and rough SB steps. The anisotropie surface stress tensor leads to interactions between the steps, which can be characterised by assigning a force monopole and a force dipole to each step. The monopole-monopole interaction describes the repulsion, the monopole-dipole interaction the attraction between adjacent steps. From STM images the distribution of the step-step separation was extracted. Using this distribution the value of the force monopole and the force dipole has been calculated. It was found that the short range monopole-dipole interaction attracts the SB step towards the lower lying SA step, which results in the formation of DB steps at a miscut angle of 5°