EXPERIMENTAL ENERGY-BAND DISPERSIONS AND LIFETIMES FOR VALENCE AND CONDUCTION BANDS OF COPPER USING ANGLE-RESOLVED PHOTOEMISSION

Energy-band dispersions and electron lifetimes have been determined for both valence and conduction-band states of copper using angle-resolved photoemission with polarized synchrotron radiation in the 5h35 eV photon energy range. Dispersion relations for the occupied s-p and 3d bands of Cu along the -X and -L symmetry lines (including critical points at X, and L) have been determined with an accuracy of 0.05-0.1 eV and 5% of the zone-boundary momentum. Band symmetries have been deduced using polarization selection rules. The dispersion relation has also been accurately determined for the unoccupied 1 conduction band along -X at 10-15 eV above the Fermi energy EF; this band has a reduced effective mass (m*0.90-0.94) which is related to self-energy effects. Lifetimes have been directly measured for excited hole states (the lifetime broadening h increases from 0.2 to 0.5 eV full width at half maximum for d-band energies from 2 to 5 eV below EF) as well as for excited electron states in the 1 conduction band (e1.0-2.0 eV for energies 10-15 eV above EF). The energy dispersion and h-dependent photoionization cross section of the s-p surface state on Cu(111) are reported. Previous theoretical and experimental studies of copper are compared with our accurate E vs k dispersions. © 1979 The American Physical Society.