Reconstruction, step ordering, and frustration on vicinal GaAs surfaces

The interaction between the step array and the terrace reconstruction of vicinal surfaces is evaluated by measuring with reflection high-energy electron diffraction the variation with the misorientation angle of the regularity of the steps and of the stability of the reconstruction. We demonstrate on GaAs{}(001) surfaces that the configurations for which the mean terrace width is a multiple of the reconstruction unit mesh, predicted by theoretical calculations to be energy minima, are a sharp optimum for both the step array and the reconstruction. A few minutes of arc away from this optimum, the steps modify the domain of existence and the coherence length of the reconstruction and the reconstruction modifies the step arrangement. This is clear experimental evidence that such configurations also minimize the mutual frustration of the two-ordered structures, step array, and terrace reconstruction.