engleski

XRD line profile analysis of tungsten thin films

Thin tungsten films were deposited onto glass substrates by DC magnetron sputtering at different substrate temperatures (77 K, 293 K, 523 K) and at different working-gas pressures in the range 0.7-2.8 Pa. Samples were characterized by the X-ray diffraction (XRD) which was subsequently refined with the Rietveld method. The diffracting domain size and the root mean square (r.m.s.) microstrain have been determined examined using different line profile analysis methods ( the Rietveld method, "single-line" method, Scherrer method and "double-Voigt" method). Also, the dependence of structural parameters on deposition conditions has been investigated, as well. It was found that residual stress and lattice parameter are correlated. We suggest that the observed increase of lattice parameters in comparison to the bulk values occured due to the substitutional incorporation of Ar atoms, and W atoms resided in auto-interstitial positions. The high values of r.m.s. microstrain, 0.251 % for b-W and 0.345 % for a-W, on average, confirmed this feature. All films containing predominantly the a phase showed a strong á110ń preferred orientation ; the b phase has a á200ń texture. The a phase is predominantly found at low Ar pressure, while the increase of the latter causes the increase of the fraction amount of b phase. The substrate temperature also exhibits an impact on the phase composition. The size-microstrain analysis showed the larger domain sizes and smaller r.m.s. microstrain of b phase compared to the a phase. The ratio of average volume-weighted domain sizes of a and b tungsten, Da211/Db200, is correlated with the ratio of relative fractions of a and b, Wa/Wb. deposition conditions. The goal of this work was to investigate

Tungsten thin film; X-ray diffraction; Phase composition

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