First AFM observation of thin cermet films close to the percolation threshold using a conducting tip

Optical, electrical and magnetic properties of cermet thin films (metallic nanograins embedded in an insulating matrix) are strongly dependent on their morphology. The size, share and distribution of metallic grains are the main parameters as well as roughness of the surface of the samples. Usual techniques such as transmission electron microscopy, scanning electron microscopy, atomic force microscopy, while very useful to characterize some of them, are inefficient for others and have to be used in a complementary way. Until now, it was impassible to point out metallic nanograins from the matrix using a commercial setup. We have developed a new technique of local contact resistance measurements with a conducting tip AFM called "Resiscope". In this paper, we show the first electrical mapping obtained with our setup on gold-alumina and nickel-alumina cermet, with different filling factors, very close to percolation threshold and we briefly correlate these observations to magnetic properties. (C) 2000 Else Elsevier Science B.V. All rights reserved.