Analysis of Nitrogen, Boron, and Hydrogen of i-BN Films Fabricated by the Ion Beam Assisted Deposition
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ANALYSIS OF NITROGEN, BORON, AND HYDROGEN OF i-BN FILMS FABRICATED BY THE ION BEAM ASSISTED DEPOSITION J-P. Hirvonen* and J.K. Hirvonen** *Department of Physics, University of Helsinki, 00170 Helsinki, Finland "**Spire Corporation, Patriots Park, Bedford, MA 01730 ABSTRACT The concentrations of the main constituents of hard i-BN films produced by the ion beam assisted deposition were measured using the nuclear resonance reactions 1 1 B(p,y) 1 2 C at Ep = 163 keV, and 15 N(p,cq) 12 C at Ep = 429 key, respectively. The hydrogen contamination of the samples was investigated using the forward recoil spectroscopy (FRES) technique with a 2 MeV He+ beam. Some complementary analyses of carbon and oxygen were performed using (d,p) and (d,a) -reactions. Hyperstoichiometric boron concentration were found in almost all films. The relative concentrations of nitrogen and boron were also slightly dependent on the deposition conditions as well as the deposition temperature. Contrary to this, hydrogen contamination, that was generally at a low level with few exceptions, was more independent of these parameters. INTRODUCTION Strong activation involved in many ion beam assisted deposition processes does not only improve the quality and performance of stable compound films, e.g. titanium nitride, but also allows the formation of metastable structures with novel properties. Among these, diamond and diamond-like, as well as hard boron nitride films, are of special interest due to the many superior characteristics. Deposition of compound films is generally complicated because beside of many other parameters the composition of the film must be controlled with a good accuracy. Ion beam processes, being normally far from the equilibrium conditions, require special attention in this respect. The increased chemical activity of ionized species also attracts many impurities, and contamination with carbon, oxygen, and hydrogen are common in many practical coatings (1]. In this study we have analyzed the boron and nitrogen concentrations in BN films produced by ion beam assisted deposition (i.e. i-BN films). It is assumed that the main properties of the films is determined by the boron to nitrogen ratio. That is why the effect of the process parameters on this ratio is essential to know. In addition, impurities, especially the hydrogen contamination, was examined. Hydrogen is known to posses the active role in hydrogenated i-C films occupying unfilled tetrahedral bondings [2]. On the other hand, in ionplated hard BN films deposited using NH3 gas, high concentration of hydrogen has been observed [2]. Moreover, IR spectroscopy has revealed H-B bonding in these films [2]. For this reason, the incorporation of hydrogen could be expected also in the case where hydrogen is available only as a contaminant in the process.
Mat. Res. Soc. Symp. Proc. Vol. 128. t1989 Materials Research Society
86
METHODS AND MEASUREMENTS Hard i-BN films were produced on silicon substrates by ion beam assisted deposition. Boron was evaporated with an electron beam gun si
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