  In low-temperature pulsed growth two-dimensional islands form and coarsen
into ~10 nm features. The islands produce well-defined displaced x-ray
diffraction peaks due to relaxation of anisotropic surface stress of the (2x1)
reconstruction with expansion and contraction present in orthogonal directions.
The relaxation carries over into multilevel islands, suggesting that domains in
subsequent layers form metastable stress domains. We infer that the island
distribution differs from continuous deposition, enhancing the population of
monodisperded islands exhibiting anisotropic relaxation.
