Vectorial Photoelectric Effect

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Abstract
Experimental results and their analysis are presented which indicate that the vectorial photoelectric effect originates neither in excitation at the surface nor in pure volume optical absorption, but is a unique combined surface-volume effect which depends only on optical absorption as influenced by the interface. This effect can be phenomenologically regarded as surface-enhanced optical absorption (SEOA) in which, for certain transitions excited by light polarized perpendicular to the surface, optical absorption in the volume near the surface can be increased manifoldly (100 times or more) by the presence of certain surface conditions. Our results show a large decrease in this absorption by controlled modification of the surface for the system investigated, which is single-crystal silicon in ultrahigh vacuum with surfaces oriented parallel to (111), (110), and (100) planes. Photoelectric yields are shown at angles of incidence from 0° to 60° for both polarized and unpolarized light with photon energies in the range 4.6-6.4 eV. Some interface effects are illustrated by photoemission from samples covered with thin (20-100 Å) oxide layers; electron emission is considered in terms of the system silicon-silicon oxide-vacuum. Essential requirements are discussed for a theory of SEOA, the existence of which calls for a reexamination of present approaches to the fundamental theory of photoelectric emission.

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