日本金属学会誌

J. Japan Inst. Metals, Vol. 59, No. 8 (1995),
pp. 851-856

Low Energy Nitrogen Implantation into Iron and Iron-Titanium Alloy Thin Films

Saburou Ohtani, Masanori Watanabe and Nobuya Iwamoto

Ion Engineering Research Institute Corp., Osaka

Abstract:

To solve the problems such as shallow and nonuniform distribution of implanted atoms, implantations with a low acceleration voltage ranging from 200 to 2000 V into Fe, Fe-9 at%Ti and Fe-19 at%Ti evaporated thin films held at the temperatures ranging from 270°C to 400°C were conducted. The effects of substrate temperatures, the implantation energies and current densities on the depth profiles of implanted nitrogen atoms were examined using secondary ion mass spectroscopy. Binding energies of N 1 s electron and crystal structures of the implanted layers were also examined using X-ray photoelectron spectroscopy and X-ray diffraction, respectively. When the substrates were kept at 300{~}400°C, the redistribution due to the diffusion effect of the implanted nitrogen atoms was observed even when the energy as low as 1000 eV was used. Although the nitrogen atoms implanted in the Fe thin films showed nonuniform distribution, almost homogeneous and deep distributions of the nitrogen atoms were obtained in the case of the Fe-9 at%Ti thin films. This can be attributed thermodynamically to the preferential binding between titanium and nitrogen atoms. It was, however, recognized that the depth profiles of the nitrogen atoms implanted into the Fe-19 at%Ti thin films became shallower than those into the Fe-9 at%Ti thin films. It can be considered that the reason why the diffusing movement of the implanted atoms occurred at a lower temperature than that of ion-nitriding treatment is due to nonnecessity of the nitride formation at the substrate surface by forcing direct implantation of nitrogen atoms into surface layers.


(Received December 19, 1994)

Keywords:

ion implantation, nitrogen, depth profile, nitride, iron-titanium alloy, low energy, diffusion


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