THE TEMPERATURE COEFFICIENT OF RESISTANCE IN ULTRATHIN, EVAPORATED METAL FILMS (INVESTIGATION OF METAL THIN FILM FORMATION AND STRUCTURE).

Book excerpt: It is known that some of the abnormal magnetic properties of ultrathin metal films, and their electrical conduction mechanism, can be explained on the basis of their "island" structure. It can be shown that the electrical conductivity and the temperature coefficient of resistance are controlled principally by the radius of the islands and the distances between them. By suitably adjusting these structural parameters, both of which enter the relation for the film conductivity exponentially, one can be made to predominate over the other. Thus, if the islands and the distances between them are small, very large negative temperature coefficients are observed. On the other hand, if the islands are very large or the thermal expansion coefficient of the substrate is unusually high, positive temperature coefficients can be observed, often several times larger than even the bulk values, even for films of resistances as high as 10 to the 6th power omega/square or higher.