Surface chemical changes induced by low‐energy ion bombardment in chromium nitride layers

Abstract

AbstractIn this work three types of CrNx layers—one close to Cr2N, the other to CrN and a third with high nitrogen content CrN1+x—were prepared by reactive magnetron sputtering. The samples were subjected to bombardment by Ar+ and N2+ ions applied in sequence. The relative atomic concentration and the chemical states of the elements in the surface layer were determined by x‐ray photoelectron spectroscopy. Alternate bombardment with Ar+ and N2+ ions (1–2 keV) resulted in significant compositional and chemical state changes. Although prolonged Ar+ bombardment did not decrease the nitrogen content of Cr2N below the nominal (CrN0.5) composition, it decreased the nitrogen content of the closely stoichiometric CrN appreciably, to about CrN0.8. At bombardment with N2+ ions nitrogen could be implanted into the Cr2N films, changing its composition up to about CrN0.8. It was shown that extra nitrogen could be incorporated also into the CrN samples, increasing the nitrogen content above the stoichiometric composition up to about CrN1.2. The CrN1+x‐type sample showed high stability towards Ar+ bombardment. Two significantly different chemical states of nitrogen were determined for the two types of nitrides: the N 1s peak at 397.5 ± 0.1 eV binding energy was characteristic of N in Cr2N and the peak at 396.5 ± 0.1 eV of N in the CrN state. The effect of Ar+ and N2+ bombardment on the surface composition discussed in this paper may provide information for elaboration of deposition conditions for CrNx coatings with predetermined chemical composition and structure. Copyright © 2002 John Wiley & Sons, Ltd.