Electronic structure of insulatingZr3N4studied by resonant photoemission

The formation of insulating ${\mathrm{Zr}}_3$ ${\mathrm{N}}_4$ by low-energy (5 KeV) ${\mathit{N}}_2^{+}$ bombardment of zirconium was studied by photoemission spectroscopy using synchrotron radiation. The electronic structure of ${\mathrm{Zr}}_3$ ${\mathrm{N}}_4$ was then studied by resonant photoemission in the 32–80-eV photon-energy range. Resonance effects have been observed at ∼41 and at ∼50 eV, well above the Zr 4p binding energy (∼29.5 eV) as measured by photoemission. The resonance at 41 eV is shown to be associated with the enhancement of those valence-band states with an important Zr 4d character. In fact, it has been used to isolate the cationic Zr 4d contribution to the valence band of ${\mathrm{Zr}}_3$ ${\mathrm{N}}_4$. Furthermore, we have identified those regions of the valence band with a predominant N 2p character by direct photoemission at hν≥70 eV for which the Zr 4d photoemission cross section is negligible. A broad resonance at hν=50 eV seems to be caused by resonant processes involving N 2p states, however, the exact mechanism implicated remains unknown.