Surface states in Si(111)2×1 and Ge(111)2×1 by optical reflectivity

Surface states in Si(111)2×1 and Ge(111)2×1 are detected by the method of the change of external reflectivity, both at energies below and above the gap. Optical transitions at 2.6 eV in Si and at 1.8 eV and 3.1 eV in Ge, as well as the already known transitions below the gap are observed.