On the Hall effect and resistivity of nanocomposite Ni-SiO2 thin films

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