engleski

XRD analysis of tungsten thin films

The properties of dc-magnetron sputtered thin tungsten films depend very strongly on deposition conditions. Depending on Ar gas pressure, substrate material, substrate temperature and deposition duration, there is a different relative amount of beta- and alpha-W phase deposit. In this work tungsten thin films prepared under different conditions of working-gas pressure and deposition temperature were investigated by means of X-ray diffraction (XRD) on a Philips powder diffractometer (PW 1820) and subsequently refined by the Rietveld method. The goal of this work was to investigate the dependence of microstructure and phase composition on deposition condition. Moreover, the microstructure, size and microstrain were extracted by different methods: Rietveld method, single-line method and Warren-Averbach method. The structures were refined in the space group of  -W, Im-3m and  -W, Pm-3n. The quantitative phase composition was estimated from refined values of scale factors according to the procedure of Hill and Howard. It was found that at the deposition temperature of 293 K, on increasing the working-gas pressure, the amount of  -W phase increases. However, at low (77 K) and high (523 K) deposition temperature, on increasing the working-gas pressure, there is a sudden decrease in the amount of  -W phase at 1.4 Pa, then a further increase of working-gas pressure yields to the increase in the amount of  -W phase. The lattice parameters of alpha and beta tungsten film decrease with the increasing of working-gas pressure. The results of size-strain analysis, volume averaged grain size and r.m.s. microstrain obtained by different methods used in this work are in good agreement.

Tungsten thin film; X-ray diffraction; Phase composition

nije evidentirano