Phase formation and diffusion after nitrogen PIII in molybdenum

Abstract

Using nitrogen plasma immersion ion implantation into Mo, the nitride phase formation and nitrogen diffusion behavior were investigated in the temperature range from 330 to 580 °C. In all cases, the formation of a new phase (beside the Mo substrate) was observed with X-ray diffraction. Good agreement of this phase with powder diffraction files of cubic Mo 2N was found, albeit the exclusion of a slightly distorted tetragonal modification was not unequivocal due to the low signal intensity. Elastic recoil detection analysis indicated a surface nitrogen concentration of 35–40 at.%. The thickness of this surface layer was always larger than the projected range, as calculated with TRIM, and it increased with longer process time or higher temperature. In addition to this diffusion process, the formation of a deep tail of nitrogen into the bulk Mo was observed, starting near a temperature of approximately 500 °C.