Strong and unequivocal polarization effects are observed on the photoemission spectra of vacuum-cleaved, (1010) Tellurium. Calculations of the energy distribution curves of the photoelectrons have been performed based on pseudopotential band structure and wave functions. The results correlate with the observations and allow for the interpretation of the measured EDC in terms of bulk properties and surface effects.

The influence of different types of short range order on the density of states of tellurium is investigated. The results for usual trigonal short range order are compared to those for simple cubic short range order. The density of states for the corresponding systems without long range order is discussed within the framework of the complex band structure method. The results are compared to photoemission experiments for different modifications of disordered tellurium.

The electronic density of states of trigonal and amorphous tellurium and selenium are calculated in the energy region of the two-highest-valence-band triplets and the two-lowest-conduction-band triplets. The calculations are performed using the pseudopotential scheme. The structural model for the amorphous phases is based on the assumption that the average short-range order is the same as in the trigonal crystals. The main results are that (i) the density of states of the amorphous phases of both materials is essentially structureless in the energy region of the second-conduction-band triplet; (ii) some fine structure is maintained in the two valence bands and the first conduction band. These can be associated with parts of the density of states contributed from a region of the Brillouin zone along the ${k}_{z}$ axis. The results are compared to those obtained by using a tight-binding approximation. The comparison with experimental data will be performed in an accompanying paper.

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.

AbstractThe densities of states of crystalline and amorphous Gap, GaAs, GaSb, InP, InAs, and InSb have been calculated using the pseudopotential method and the complex band structure (CBS‐)method. The short range order of the amorphous structures has been taken into account by an approximative correlation function.

The dielectric constant of amorphous selenium is calculated in the region from 2 to 10 eV using a pseudopotential formalism to calculate "lifetimes" of electrons in the amorphous state. Spicer's "nondirect transition" model is checked and modified to include energy-dependent matrix elements.