Structural and electrical properties of chromium and nickel films evaporated in the presence of oxygen

Electron-optical investigations of Cr films evaporated in the presence of oxygen (1 × 10^-7 to 5 × 10^-7 torr) have shown that the negative temperature coefficient of resistivity (TCR) is caused by small amounts of an amorphous oxide. On annealing these films in a vacuum of better than 5 × 10^-9 torr (e.g. for 140 h at 395°C) the amorphous phase crystallized and could be identified as Cr₂O₃. When Ni is evaporated in the presence of oxygen the TCR changes from positive to negative values at about 5 × 10^-5 torr. Since the negative TCR of oxygen-doped Cr-Ni (60/40) films did not change after annealing these films in a hydrogen atmosphere at 300°C (reduction of Ni oxide) it becomes plausible that the negative TCR of the Cr-Ni films, too, is caused by an amorphous Cr oxide surrounding the metal crystals.