Table I。 Binding Energies of Si 2p Line Corresponding to Different Binding States

Si-binding state Si  2p  binding  energy (eV) Si 99。5  ± 0。2

TiSi2 98。8

Si3N4 101。7  ± 0。2

SiO2 103。5  ± 0。2

(see Ref。 [17] and references   therein)。

Fig。 4。 X-ray photoelectron spectra of the Si 2p region from nc-(AlTi)N/a-Si3N4 nanocom- posite coating deposited by the LARC® technology in the π 80 coatings unit after  subtraction of the contribution from the MgKα3,4  and Kα5,6  satellites of the Al 2s line。 The same data

fitted by Savitzky–Golay and by FFT-Filter functions(19) using a linear background subtrac- tion。 The coating was polished and sputter cleaned prior to the measurement。

the signal from plasmon loss peaks of the Al 2p。 Therefore very long time of the measurements are needed in order to distinguish if the signal with binding energy of about 98。8 eV (which was attributed to TiSi2 by several researchers including our studies and which is close to that of elemental silicon, see Table I) is due to TiSi2 phase or to the Al 2s MgKα5,6 satellite。 For nc-(Ti1−x Alx )N/a-Si3N4 coatings deposited in the unit “MARWIN” (Fig。 2) we have shown that there is no noticeable amount of such “metal- lic Si” phase。(18)

In course of the present study we used silicon free (Al1−x Tix )N coatings with x ≈ 0。35 as in the nanocomposites to measure the exact structure  of  the  XPS  spectra  in  that  range。   Thus  it  was  possible       to

normalize the Al 2s signal from these  coatings  to  that  from  the  nc- (Al1−x Tix )N/a-Si3N4 nanocomposites and subtract the contribution of the Al 2s–MgKα5,6 satellite and of the Al 2p plasmon loss signals from the spectrum of the nanocomposite。 Figure 4 shows a typical example of XPS spectra of the Si 2p region for coatings deposited in the new π 80 unit。 One can see that the only peak is due to “non-metallic Si” bonded as in Si3N4 and there is no any noticeable contribution of the “metallic Si” phase。 For

Fig。 5。 XPS spectrum of the Si 2p region from a Ti–Si–N coatings deposited by magnetron sputtering at a relatively low nitrogen partial pressure and low deposition temperature。

comparison, Fig。 5 shows a nc-Ti–Si–N coating deposited by magnetron sputtering at a relatively low pressure of nitrogen and deposition temper- ature of about 400◦C that contains as a dominant Si-phase the “metallic” TiSi2。

3。2。Microstructure

Figure 6 shows a typical medium resolution transmission electron micrograph and Fig。 7 the X-ray diffraction pattern of the nc-(Al1−x Ti) N/a-Si3N4 superhard nanocomposites that was taken under glancing inci- dence (angle 1。5◦) in order to reduce the Bragg reflections from the sub- strate made of cemented carbide (WC–Co)。 We show as example the XRD pattern after the coatings were annealed to 1200◦C。 As deposited coatings have shown identical pattern, from the micrographs, one notices a fairly regular shape and uniform size of the nanocrystals as already found earlier for nc-(TiN/a-Si3N4)。(20) The crystallite size determined from the micro- graph of about 3–4 nm agrees well with that determined from the broad- ening of the Bragg reflections in the XRD pattern using Warren–Overbach Fourier transform method (see also Ref。  20 for     nc-TiN/a-Si3N4)。