TEM investigation of nitrogen-implanted Mo foil

Abstract

The synthesis and analysis of molybdenum nitrides formed during nitrogen ion implantation were investigated. Molybdenum foil samples were annealed in vacuum at 1750 °C in order to grow large grains with low index preferential orientations. For comparison purposes, thin specimens were also cut from a (110) molybdenum single crystal. These samples were implanted with nitrogen at room temperature as well as at an elevated temperature of 370 °C. Doses of 1×10 17 N + cm −2 and 5×10 17 N + cm −2 were used at accelerating voltages of 50 kV and 100 kV. One nitride phase (MoN) and an unidentified phase were observed under the prevailing conditions. The morphology and orientation relationships of nitride precipitates in the Mo lattice were examined by transmission electron microscopy and electron diffraction. Depending on the surface orientation, both the Bain and the Nishiyama–Wassermann orientations occurred. Implantation at 100 kV resulted in small misorientated MoN precipitates that showed recrystallization and reorientation after annealing at 900 °C. Pulsed electron beam annealing (PEBA) at 0.6 J cm −2 did not affect the nitride precipitates but restored implantation damage in the molybdenum lattice.