3.2. Chemical composition
Table 1 shows the chemical composition of the films as a function of ton. Since the RBS analyses do not show a variation of the concentration versus the depth profile, it Simeprevir must be pointed out that the chemical composition is an average value on the whole film thickness. As it could be expected, the RBS results indicate the presence of three elements, i.e. iron, nitrogen and oxygen. No trace of minor elements has been detected in the film (detection limit about 1 at.%). The iron content is slightly decreasing with increasing oxygen content from 15.7 to 34.7 at.%. Similarly, the nitrogen content is decreasing from 33.9 to 20.9 at.%. The ratio Fe/(N + O) of the films is ranged from approx. 1 to 0.8 ( Fig. 3).
Fig. 3. The ratio Fe/(N + O) in various films as a function of ton.Figure optionsDownload full-size imageDownload high-quality image (89 K)Download as PowerPoint slide
Therefore, the sum of the nitrogen and oxygen concentration is about 50 at.%. Obviously, except the film deposited with ton = 10 s, all the films are iron understoichiometric ( Table 1) compared to the chemical formula type of ~ 1:1 Fe(O,N) stoichiometry. It is well established large intestine wüstite has a rocksalt-like structure with Fe and O forming non-stoichiometric Fe1 − xO. The wüstite has Fe vacancies in an ordered distribution and the fraction of Fe is ranged from 0.94 to 0.87 . Such kind of structure is also encountered for iron mononitride . Using RBS data of Table 1, we can expect the formation of the non-stoichiometry Fe1 − xO and vacancies. Hence, the chemical formula of the iron oxynitride layers can be written as Fe1 − xNyO1 − y.