COSEGREGATION OF TUNGSTEN AND NITROGEN ON FE-9-PERCENT-W-N(100)

Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) have been used to study the cosegregation of tungsten and nitro gen on ferritic Fe-9%W-N(100) single crystals with nitrogen contents r anging from c(N)=11 to 51 wt-ppm. Cosegregation occurs at temperatures T less than or similar to 600 degrees C depending on the nitrogen con tent. The thickness of the cosegregated surface layer is estimated by means of Ari ion depth profiling as being less than two atomic layers. The LEED pattern of the tungsten and nitrogen covered Fe-9%W-51ppmN(1 00) substrate shows a sharp (1 x 1) structure at a low background inte nsity indicating epitaxial stabilization of the cosegregated tungsten nitride layer on the bcc (100) surface. The tungsten and nitrogen cove red Fe-9%-11ppmN(100) substrate exhibits a c(2 x 2) structure. On Fe-9 %W-51ppmN(100) a temperature-driven phase transition between the coseg regated (1 x 1) and c(2 x 2) surface phases is observed.