7×7 Reconstruction of Ge(111) Surfaces under Compressive Strain

Abstract
We have discovered a correlation between lateral compressive strain in an elemental material and the reconstructed state of its surface. We studied continuous films of pure Ge epitaxially grown on Si(111) substrates. The in-plane lattice parameter varies continuously with film thickness while the surface symmetry changes from c2×8 to 7×7. The results indicate an important role of lateral compressive stress in the 7×7 reconstruction.