Temperature-dependent electronic excitations of the Si(111)2×1 surface

Electron-energy-loss measurements on cleaved Si(111) 2×1 surfaces show a temperature dependence in the position and shape of the absorption edge of the 0.5-eV surface-state transition. The observed trends in the onset line shape provide experimental evidence for surface-state excitonic polarons. In addition, a lower-lying, defect-related surface-state transition at 0.35 eV is studied at low temperature and found to have localized character. © 1985 The American Physical Society.