THE INTERACTION OF N WITH TI AND THE OXIDATION OF TIN STUDIED BY SOFT-X-RAY ABSORPTION-SPECTROSCOPY

The N1s XAS spectrum of a reference TiN sample is compared to an N p-p rojected DOS. Good overall agreement is found except for a small discr epancy at the edge which could be due to core-hole effects. The N1s XA S spectra of N, chemisorbed on Ti (3000 L) and N+ implanted in Ti (250 eV) compare well with TiN; this indicate a close chemical similarity between them. The differences in the spectra are attributed to disorde r in the implanted layer and to the two-dimensional character of the c hemisorbed layer. The N1s XAS spectra of TiN oxidized at different tem peratures indicate that 0 progressively displaces N to form TiO2. The results are consistent with a complete TiN/TiO2 phase separation and r ule out the possible formation of oxynitride. The appearance of a narr ow peak in the spectrum of TiN oxidized at 300-degrees-C suggests that some of the N atoms displaced during the oxidation process remain rel atively unbound within the TiO2 matrix. At 500-degrees-C this peak dis appears; this is attributed to N migration towards the surface followe d by thermal desorption.