A COMPARATIVE-STUDY OF THIN COATINGS OF AU PD, PT AND CR PRODUCED BY MAGNETRON SPUTTERING FOR FE-SEM/

Visualization of structural details of specimens in field emission sca nning electron microscopy (FE-SEM) requires optimal conductivity. This paper reports on the differences in conductive layers of Au/Pd, Pt an d Cr, with a thickness of 1.5-3.0 nm, deposited by planar magnetron sp uttering devices. The coating units were used under standard condition s for source-substrate distance, current, HT and argon pressure. Carbo n films, deposited by high-vacuum evaporation on small, freshly cleave d pieces of mica, were used as substrate and mounted on copper grids f or TEM and SEM inspection. Au/Pd, Pt and, to a lesser extent, Cr coati ngs varied in particle density, size and shape. Au/Pd coatings have a slightly more granular appearance than Cr and Pt coatings, but this is strongly dependent on the type of sputtering device employed. In FE-S EM images there is almost no difference in contrast and particle size between the Au/Pd layer and the Pt layers of a similar thickness. The nuclei of Au/Pd are rather small with almost no growth to the sides or in height, making Au/Pd coatings a good alternative to chromium and p latinum for FE-SEM of biological tissues because of its higher yield o f secondary electrons.