Electrical and microwave characterization of kanthal thin films: temperature and size effect

Thin films of kanthal of thicknesses varying from 10 to 200 nm were deposited onto clean glass plates and alumina substrates by flash evaporation in a vacuum of 3 x 10(-5) Torr. The in situ resistance of as-grown films measured at various temperatures revealed that these films were stable at high temperatures and had negligible TCR. The thickness dependence of conductivity was also measured and it was observed that it obeyed the Fuch-Sondhimer (FS) theory of electrical conduction of metallic films. The surface resistivity of these films was estimated from the AC conductivity measurements carried out using an LCR meter. The microwave absorption properties of these films at various thicknesses coated onto the walls of a Ku-band cavity were measured in the frequency range 16.3-17.5 GHz. The skin depth of the film (which is different from that of the bulk material) was estimated in the light of the measured values of the DC and AC conductivity of the film and a theoretical explanation for the observed thickness dependence of microwave loss has been presented. (C) 1998 Elsevier Science S.A. All rights reserved.