Direct Evidence for Disorder Effects on the Electronic Structure of Selenium

Abstract
The electron states of amorphous and single-crystal trigonal selenium were investigated by high-resolution photoemission spectroscopy. Structures due to a high density of states 0.2 eV below and 6.9 eV above the valence-band edge for crystalline Se are absent in the amorphous phase, but structures due to deeper valence-band density-of-states features remain. The results provide the first direct evidence for disorder effects on the Se valence and conduction bands and agree with calculations for amorphous Se using a pseudopotential formalism.