Nitriding of zirconium and aluminium by using ECR nitrogen plasmas

Surface nitriding of zirconium or aluminium was performed by irradiation with the nitrogen plasmas produced in an ECR plasma apparatus. The degree of zirconium nitriding was enhanced by the application of negative bias voltage to the substrate and by the use of a discharge with relatively low gas pressure. Optical emission spectroscopy showed that the nitrogen ion, N-2(+), was more effective for surface nitriding than was the excited species, N-2*. For aluminium, pre-sputtering by argon plasma bombardment was performed before the nitriding process. The aluminium surface was weil nitrided when this pre-treatment was followed by nitrogen plasma irradiation with the substrate negatively biased.