The Application of Spark Erosion to the Synthesis of Thin Films Containing Ultrafine Particles

Abstract

We have investigated a new method of preparing granular thin films, which are composed of fine metallic particles embedded in a uniform matrix material. By our method, fine metallic particles are created by spark erosion in an inert gas environment and directly deposited onto a cooled substrate. Magnetron sputtering is employed concurrently thereby building up the matrix. Using such a deposition method, granular thin films are created without the need of any heat treatments and can be made with virtually any material and composition. Furthermore it is even possible to create granular thin films from miscible phases. The size of the particles can be controlled by varying the pressure under which the spark erosion is conducted up to a few Torr of Ar. We have applied our method to the case of magnetic particles in a nonmagnetic matrix. Preliminary TEM measurements on Fe particles in a Cu matrix showed 10 nm diameter Fe particles. SAD patterns show that the film is composed of only the Fe and Cu phases. Similarly for the Gd-Ag system, 10 nm Gd particles were observed in an Ag matrix. Gd-Ag compounds that would be expected to form were not observed. Magnetic measurements for these systems agreed with the nanometer scale microstructure that was observed.