ON THE HALL-EFFECT AND RESISTIVITY OF NANOCOMPOSITE NI-SIO2 THIN-FILMS

Granular metal films with nanocrystalline to amorphous structure are o f great interest for applications in the field of miniature sensors. T hese materials exhibit important changes in their physical properties when the volume fraction of metal decreases under a critical value, kn own as the percolation threshold. This paper presents some results con cerning the galvanomagnetic properties and electrical conductivity of Ni-SiO2 granular thin films. These properties have been investigated f or films with metal contents between 40 and 60% and they reflect the m etal-insulator transition. The films are prepared by r.f. sputtering i n Ar atmosphere (p similar to 1 Pa), using composed targets. The Hall measurements are made at room temperature, for magnetic-field inductio n values up to 2 T. The results of the resistivity and Hall voltage me asurements and their dependence on the metal content in films reflect the metal-insulator transition. The changes of the resistivity and mag netic behaviour of Ni-SiO2 granular films, near the percolation thresh old, make these films interesting for the field of thin-film sensors(t emperature sensors, Hall sensors). (C) 1998 Elsevier Science S.A. All rights reserved.