Valence-band structures of phosphorus allotropes

X-ray photoemission spectra (XPS) of several forms of phosphorus have been measured with the use of a monochromatized $\mathrm{Al}K\alpha$ x-ray source with a resolution of ∼0.6 eV full width at half maximum. We have investigated orthorhombic black phosphorous, cubic white phosphorus, and triclinic Na${\mathrm{P}}_{15}$ as well as bulk amorphous red phosphorus and plasma-deposited hydrogenated amorphous thin films, and present the first published XPS spectra of most of these allotropes. We also report the results of electronic structure calculations for orthorhombic phosphorus and for the tetrahedral ${\mathrm{P}}_4$ molecular constituent of cubic white phosphorus ($w$-P). Differences in densities of states are interpreted in terms of the different bonding configurations of the various allotropes. The spectra of black P is fitted well by the calculated valence bands. The spectra of amorphous P are not inconsistent with the presence of pentagonal tubes of phosphorus atoms as they are present in Hittorf's phosphorus and in Na${\mathrm{P}}_{15}$. The electronic structure of $w$-P is well described by that of isolated ${\mathrm{P}}_4$ tetrahedra.