Studies on plasma-nitrided iron by scanning electron microscopy, glancing angle x-ray diffraction, and x-ray photoelectron spectroscopy This article presents the results of a study of the plasma characteristics of an electron cyclotron resonance plasma source used for nitriding pure Fe. Diagnostic measurements, using optical emission spectroscopy, Langmuir probes, and an ion analyzer, were recorded as functions of the working pressure (2 -8ϫ10 Ϫ4 Torr͒ and the external magnetic field near the substrate ͑from the extremes of highly compressed and divergent plasma fluxes͒. It was observed that the plasma source is capable of producing high density discharges, about 5ϫ10 11 cm Ϫ3 and ion energies about 15-48 eV. The ion energy was highest for the case of a divergent plasma (ϳ45 eV͒. The most abundant excited radicals produced in the N/H discharges were the NH, N 2 and N 2 ϩ species. Experiments for nitriding of Fe showed the formation of distinct material structures dependent on the plasma conditions. Conditions were found for which it was possible to form almost single phases of Fe 3 N and Fe 16 N 2 in the sample surface.

The description and performance characteristics of a microwave electron cyclotron resonance (ECR) overdense plasma source are presented. The discharge was generated by introducing the circular TE11 mode wave at a frequency of 2.45 GHz into a cylindrical cavity, which is inmersed in an external static magnetic field from three solenoid coils. For magnetic field values corresponding to the ECR condition, and at pressures 10−4–10−2 Torr, in argon and methane the plasma initiation occurred with 10 W of incident power. The plasma density and temperature were measured using electric probes, and their dependence on the pressure and magnetic field are shown. Optical emission spectroscopy was carried out to identify chemically active species in the plasma. It was found that a high microwave power absorption level could be achieved by reducing the external magnetic field to values near half the resonant one, giving as result the production of a plasma with a density greater than the critical one (overdense plasma).

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