A structural study of the Al(111)( square root 3* square root 3)R30 degrees -Rb phase at different temperatures

摘要: Normal-incidence standing x-ray wavefield (NISXW) measurements have been made of the local adsorption site Rb on Al(111) surfaces, particularly in an ordered ( square root 3* 3)R30 degrees phase, as a function sample temperature during or subsequent annealing. The results confirm top-site occupation for low-temperature (around 150 K) preparation, but show that room-temperature preparation leads to structure having atoms surface substitutional sites. overall structural situation is therefore essentially same found previously by low-energy electron diffraction LEED Al(111)( -K phases. However, experiments involving annealing prepared room indicate only small part easily transforms higher-temperature form, and indeed there evidence even preparations some fraction adsorbed may remain atop apparent conflict this result with from recent photoemission core-level shift data discussed.