Influence of surface structural disorder on linewidths in angle-resolved photoemission spectra

Abstract

By combination of high-resolution photoemission data and linewidth analysis of low-energy electron diffraction spots we are able to derive a semiquantitative understanding of how disorder ͑induced by argon-ion bombardment and subsequent insufficient annealing͒ broadens photoemission peaks. At the example of surface states on Cu͑100͒ and Cu͑111͒ we demonstrate how the linewidth may be extrapolated to ''perfectly'' ordered surfaces in favorable cases. We also present experimental evidence that disorder-induced broadening is dominated by defect scattering of the photohole and is inversely proportional to the effective masses. Extrapolated ''intrinsic'' linewidths ͑full width at half maximum͒ are ⌫ i р(21Ϯ5) meV at ⌫ on Cu͑111͒, ⌫ i р(20Ϯ3) meV at M on Cu͑111͒, and ⌫ i р(13Ϯ4) meV at M on Cu͑100͒.

Decay of electronic excitations at metal surfaces

“…In this approach the contributions from different phonon modes, in particular the Rayleigh surface mode as well as bulk phonons and the general temperature dependence are taken into account. They also obtain the high temperature behavior represented by l. Their approach is based on: (i) Thomas-Fermi screened Ashcroft electron-ion potentials, (ii) one-electron states obtained from the model potential, and (iii) a simple force-constant phonon model calculation that gives results for the phonon spectrum in good agreement with recently published experimental data [52,86,99,100].…”

“…the influence of defects on linewidth, has been reported by Theilmann et al [86]. By combination of high-resolution photoemission data and linewidth analysis of low-energy electron diffraction spots a semiquantitative understanding of how disorder broadens photoemission peaks could be obtained.…”

“…Only few recent investigations focus on linewidths and we give a short summary on available results. Theilmann et al [86] report a linear correlation between the observed photoemission linewidth at M and the width of low-energy electron diffraction peaks. This enables the (1 1 1).…”

“…This allows an extrapolation to ''perfectly'' ordered surfaces. Moreover, experimental evidence was found that the disorder-induced broadening is dominated by defect scattering of the photohole and is inversely proportional to the effective mass of the surface state [86]. Extrapolation to minimal disorder and T !…”

“…[100], with the earlier extrapolations to optimum resolution, lowest T and ''defect-free'' surfaces. While G ee 22 meV is obtained from the data of McDougall et al [99], Theilmann et al [86] find G ee ð21 AE 5Þ meV. Recent ultra-high-resolution data [95] as function of temperature allow to separate G ee and G ep (compare Eq.…”