Photoemission Observations of ResonantdLevels andd-Band Formation for Very Thin Overlayers of Cu and Pd on Ag

Photoemission studies of very thin overlayers of Cu and Pd on Ag substrates show resonant bound $d$ states with half-widths $\Gamma \simeq 0.5, \mathrm{and} 0.8$ eV centered at 2.5 and 1.2 eV below the Fermi energy $E_{\mathrm{F}}$, respectively, for depositions ≲ 2 average monolayers, and show the formation of bulk band structure for deposition ≳ 4 monolayers. The $d$-resonance position for Pd on Ag (1.2 eV below $E_{\mathrm{F}}$) is markedly different from that of dilute Pd in AgPd alloys (2 eV below $E_{\mathrm{F}}$), while the level widths are comparaable.