Direct stress measurement of Si(111) 7×7 reconstruction

► We measured a difference in the surface stress between Si(111) 7×7 and Si(111) 1×1. ► Surface stress during Ge wetting layer growth on Si(111) 7×7 and on H-terminated Si(111) 1×1. ► Combined the surface-curvature and RHEED instrumentations in an identical system. ► Si(111) 1×1 surface releases 1.6 N/m (1.3 eV/(1×1 unit cell)) of the surface energy from tensile Si(111) 7×7 reconstruction.