Valence-band structure of amorphous germanium-nitrogen alloys

D. COMEDI; A. R. ZANATTA; I. CHAMBOULEYRON; F. ALVAREZ

Cancun

Congreso; Latin American Congress on Surface Science, Vacuum and their Applications; 1994

SLACS

The valence band structure of amorphous germanium-nitrogen alloys (a-Ge1-x Nx) of various atomic compositions (0<x<0.355) has been studied by ultraviolet photoemission electron spectroscopy using HeI (21.2 eV) and HeII (40.8eV) excitation. The photoemission spectra for samples with low N content (x lower than »0.01) essentially resemble the spectra observed for pure a-Ge. For x values exceeding  »0.01, a N-related broad band centered at about 5.2 eV below the Fermi energy is found to evolve with increasing x. For x values higher than approximately 0.1 a second band located at an energy of 10.9 eV below the Fermi level becomes  apparent. The evolution of the N-related bands with increasing x is accompanied by a gradual recession of the electron energy distribution at the top of the valence band with respect to the Fermi level. For materials having the highest N concentrations the N-related double-band structure practically dominates the photo-emission spectra. A comparison of the present results with previous similar studies in a-Si1-xNx suggests that the bands observed at energies 10.9 and 5.2 eV below the Fermi level are due to N bonding and nonbonding 2p states, respectively.