Stress Evolution during Si(111)7×7 Surface Reconstruction

We have focused on stress measurements of the reconstructed Si(111) 7×7 and the hydrogen (H)-terminated Si(111) 1×1 surfaces. In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection high-energy electron-diffraction instrumentations in an identical ultrahigh vacuum system. The surface stress behaviors during desorption and adsorption processes of hydrogen on the Si(111) surfaces reveal that the Si(111) 1×1 surface releases 1.6∼1.7 N/m (= J/m2), or 1.3∼1.4 eV/ (1×1 unit cell), of the surface energy from the strong tensile Si(111) 7×7 reconstruction.