STRUCTURE AND PHASE-TRANSFORMATIONS OF SPUTTERED NB-FE AND NB-CO FILMS

NbFe and NbCo thin films were prepared over a wide composition range by triode-sputtering at room temperature and at 300 °C, respectively. The films were investigated by X-ray measurements and transmission electron microscopy in order to study the structure and the formation range of the different phases. The results were compared with Gibbs free energy curves of the amorphous and the equilibrium phases in the NbCo system calculated by the calphad method. Contrary to the liquid alloys rapidly quenched, the solubility of the terminal phases prepared by sputtering is not enhanced up to their maximum value. The extension of the solid solution NbFe decreases for higher substrate temperatures. For Nb80Fe20 the transformation into the metastable equilibrium between the amorphous and the bcc solid solution was monitored by in-situ X-ray experiments. For the decrease of the volume fraction as well as for the Fe-concentration of the NbFe grains we found sqare-root of time laws. © 1990.