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

The temperature dependence of the surface-state electronic transition for cleaved Ge(111)-2×1 is reported and compared to previous results on Si(111)-2×1. Ge(111)-2×1 shows an almost linear dependence of the surface-state band gap between 30 and 295 K, varying between 535 and 415 meV, respectively. Cleaved Ge(111)-2×1 shows little evidence for the defect-induced states usually found, even on excellent single-domain 2×1 cleaves of Si(111). © 1986 The American Physical Society.