Depopulation of the Ag(111) Surface State Assigned to Strain in Epitaxial Films

Photoemission spectra from epitaxial Ag(111) films on Si(111)-( 7×7) show that the γ surface state in Ag(111) is depopulated in films deposited on the silicon surface when compared with ideal Ag(111) surfaces. This is interpreted as a shift of the surface state up in energy, beyond the Fermi level, since it can be partly reversed by a lowering of the work function, in accordance with phase-accumulation model calculations. This shift is ascribed, through band structure calculations, to the strain in the Ag layers induced by film growth.