L. de Greve

Quelques mesures sur des films minces de nickel

Summary In this paper the results of a research on the properties of thin nickel films formed by cathodic sputtering are given. We specially measured the electrical resistance of these films between 37 °K and 650 °C after the resistances have been sintered during 24 hours. The thickness of these films varied between 30 mμ and 700 mμ. Down to a thickness of 200 mμ the temperature coefficient α = 1/R 0 × dR/dT still showed a sudden drop at the Curie point (360 °C). Fig. 3 gives the dependency on temperature of α for different thicknesses of the films. In fig. 4 is shown how a depends on thickness before and after sintering. From this fig. can be seen that α becomes negative for films thinner than 40 mμ. Figure 5 represents the specific resistance ρ at 0 °C as a function of thickness before and after sintering.

Resistivity of Thin Nickel Films at Low Temperatures

IN an earlier communication1, we reported on measurements on the electrical resistance of thin nickel films. We found at that time that for a thickness greater than 40 mμ the films possess a positive temperature coefficient, whereas for smaller thicknesses the temperature coefficient is negative. The films were made by cathodic sputtering.

Resistivity of Thin Metallic Films

IN continuation of work carried out in this Laboratory on the electric and magnetic properties of thin metallic films1, we have now investigated the resistivity of nickel films (20 mμ–700 mμ) between – 236°C. and 400°C. The films are deposited on thin glass sheets by using cathodic sputtering in an atmosphere of hydrogen gas, carefully purified. We measured the electric resistance as a function of thickness and temperature below and above the Curie point. Between 0° C. and – 183° C., we found approximately a linear variation of the resistance with temperature. Below – 183° C. and also between 0° C. and the Curie point this is not the case. Above 358° C. the temperature coefficient of the resistance is again constant.

The liouid helium plant of the physical laboratory of the University of Louvain

A description is given of the “Collins” liquid helium plant, used as a closed cycle for the helium gas, as it has been installed at the University of Louvain since 1951.

Mesures sur la résistance électrique de films métalliques superposés

Summary In this paper an investigation on the electrical resistance of superposed metallic films formed by cathodic sputtering is described. A first series of measurements was made on copper layers on which silver layers were deposited. Afterwards the same measurements were repeated on silver films upon which copper films were laid. The resistance of these superposed films generally proves to obey the law of Kirchhoff for two resistances in parallel pretty well, especially before sintering to 300 °C. An exception must be made for the case that the first film is extremely thin. The resistance is always much smaller than may be expected according to the law of Kirchhoff.