TEMPERATURE-DEPENDENCE OF SHOCKLEY-TYPE SURFACE-ENERGY BANDS ON CU(111), AG(111) AND AU(111)

Using angle-resolved photoemission at very high resolution we have measured thermally induced energy shifts of the Shockley surface states observed around the center <(Gamma)over bar> of the surface Brillouin zones on the noble metal (111) surfaces. Based on calculations using the one-dimensional multiple reflection model we demonstrate that the observed shifts can be quantitatively traced back to the temperature-dependent shift of the relevant bulk band gaps which support these surface states. We have addressed care to a precise investigation of the <(Gamma)over bar> state on Ag(111), since conflicting results had been reported earlier. Its initial state energy at <(Gamma)over bar> is given by E(0)(T)= -(75 +/- 5) meV + (0.17 meV/K) T in the temperature range up to about 600 K.