PROBING THE CONDUCTING PATHS IN A METAL-INSULATOR COMPOSITE BY CONDUCTING ATOMIC-FORCE MICROSCOPY

We have imaged the conducting paths in a metal-insulator composite Ni- x(SiO2)(1-x), with x ranging from 0.24 to 0.576 by conducting atomic f orce microscopy (AFM). The surface morphology and the electric current between the tip and sample have been obtained simultaneously on the n anometre scale. Measurable changes of current image have been observed for x below and above the percolation threshold x(c). Our observation s imply the importance of tunnelling for all samples. The high spatial resolution of AFM combined with a conducting tip provides new insight into electron transport behaviour in metal-insulator composites at th e nanometre scale.