Structural and electrical properties of evaporated Cr-Ni films as a function of gas pressure

Electrical measurements of 60 Cr-40 Ni films evaporated in UHV or at a definite partial pressure of N₂ and He showed that all continuous films have a positive temperature coefficient of resistivity (TCR). The electron diffraction pattern of these films could be indexed tetragonal (c/a=1.36; a=5.2 Å). Chromium was precipitated after annealing the films for 6 h at 300 °C in UHV.On evaporating Cr-Ni films at an oxygen partial pressure of 1 x 10^-6 torr the TCR became negative. The films had a structure corresponding to a distorted b.c.c. Cr lattice, which did not change even after annealing for several hours at 300 °C. This is given as a reason for the better electrical stability of these films. Possible explanations for the negative TCR of films evaporated in the presence of oxygen are also discussed.