Strong subthreshold photoemission from islandsC. Pettenkofer1 and A. Otto2
1 Hahn-Meitner-Institut, SE 6 - 14109 Berlin, Germany
2 Lehrstuhl für Oberflächenwissenschaft (IPkM) Heinrich-Heine-Universität Düsseldorf 40225 Düsseldorf, Germany
(Received 19 May 2003; accepted in final form 11 December 2003)
Epitaxial silver islands of (111) orientation of 50-100 diameter and multilayer thickness grow without strain on . Besides the common photoelectron emission (PE) out of the occupied Shockley surface state S1 on strong subthreshold PE is observed at photon energies down to 0.7 below the work function of and with final energies down to 0.7 below the vacuum level of . The subthreshold PE is assigned to direct transitions into the image potential states (IS) n=1 and n=2,3,4 and an elastic escape from these states into vacuum. The escape path is tentatively assigned to the area of the slopes of the islands where the local work function is reduced.
73.20.At - Surface states, band structure, electron density of states.
79.60.Jv - Interfaces; heterostructures; nanostructures.
© EDP Sciences 2004