STABILITY OF 2-DIMENSIONAL SURFACE NITRIDES ON TRANSITION-METAL ALLOYSURFACES

The thermal stability of the two-dimensional surface nitrides CrN, MoN and WN has been studied on transition metal alloy surfaces. The surfa ce nitrides are obtained by means of cosegregation of the constituents on Fe-15%Cr-N(100), Fe-3.5%Mo-N(100) and Fe-9%W-N(100) single crystal s. The stability of the surface nitrides decreases in the sequence Cr > Mo > W, similar to the well-known three-dimensional bulk nitrides. A ll compounds exhibit 1 x 1 LEED structures, indicating epitaxial stabi lization on the corresponding substrate surface. In a narrow temperatu re range T approximate to 550 degrees C the Fe-9%W-N(100) surface show s c(2 x 2) ordering of the segregated nitrogen atoms.