Stress, resistance, and phase transitions in NiCr(60 wt%) thin films

The evolution in both stress and resistance has been investigated on sputte red NiCr(60 wt %) resistive films during annealing (temperature cycles to m aximum 700 degrees C). Aiming at the correlation of stress, resistance, and microstructure, samples from measurements to various maximum temperatures were analyzed by x-ray diffraction and transmission electron microscopy inc luding microanalysis. A series of metastable phases was found with increasi ng temperature: the as-deposited amorphous phase a, the supersaturated body -centered-cubic (bcc) solid solution alpha(ss)(Cr) (400 degrees C), and the tetragonal sigma phase (500 degrees C). This was followed by the equilibri um two-phase alloy bcc alpha(Cr) plus face-centered-cubic gamma(Ni) (600 de grees C). The phase transitions, characterized by differential scanning cal orimetry, were found to be exothermic. The transition a -->alpha(ss)(Cr) re sults in a distinct tensile-stress component due to material densification. The resistivity is sharply decreasing and the temperature coefficient of r esistance is changing from negative to positive values during the a -->alph a(ss)(Cr) transition. (C) 2000 American Institute of Physics. [S0021-8979(0 0)07004-3].