The contribution of characteristic energy losses in the core-level X-ray photoelectron spectroscopy peaks of TiN and (Ti, Al)N studied by electron energy loss spectroscopy and X-ray photoelectron spectroscopy

Abstract

The correct interpretation of the electronic relaxation of Ti compounds upon soft X-ray excitation, such as is used in X-ray photoelectron spectroscopy (XPS), is a notoriously difficult task. Previous studies of the structure and peak assignment of the core-level Ti 2 p peaks have shown that the usual methods of background subtraction and peak fitting can bring about large errors in the XPS quantification of the Ti compounds TiN and (Ti,Al)N which are produced as coatings by reactive sputter deposition. Electron energy loss spectroscopy (EELS) was performed on TiN and (Ti,Al)N coatings at high energy resolution in a scanning Auger microprobe in the reflection mode. Results are presented which show that the primary electron beam reflected from these materials exhibits very intense and characteristic energy losses due mainly to intraband transitions. The EELS measurements in conjunction with valence-band XPS studies confirmed molecular orbital (MO) calculations of the occupied and unoccupied electron states near the Fermi level of TiN. The core-level Ti 2 p photoelectrons measured by XPS suffer the same discrete electronic excitation losses identified in TiN as transitions from the t lg and t 2u MOs (derived from N 2 p, O 2 p and Ti 3 d/4 s/4 p levels) to the partially occupied 2 t 2g state at the Fermi level. Corrections of the Ti 2 p XPS spectra with the relevant energy losses obtained by EELS allow a consistent interpretation of the Ti photoemission peak structure and a considerable improvement in the quantification of the corresponding Ti compound.