Use of Photoemission and Optical Methods to Determine the Electronic Structure of Solids

Abstract

Through measurement of the energy distribution of photoemitted electrons, it is possible to obtain a measure of the probability, P(hv, E), of an electron being excited by a photon, hv, to a given final state of energy, E. By studying P(hv, E) as a function of energy, information can be obtained on the optical selection rules. Where direct conservation of crystal momentum, hk̄, provides an important selection rule, it is possible to trace out the position in energy of the bands in particular regions of the zone. Where direct k̄ conservation doesn't provide an important selection rule, the optical density of states can be obtained. In many cases, the optical density of states appears to be directly related to the band density of states. Great care must be taken for surface cleanliness in the photoemission experiments; however, this method gives considerably better resolution than any of the other experimental methods used to probe electronic structure over a wide energy range.