MICROFABRICATION OF ULTRATHIN FREESTANDING PLATINUM FOILS

In this paper a process for the microfabrication of ultrathin (5 nm) f ree-standing Pt foils is described. A Pt foil is deposited by means of laser ablation on a Si3N4 membrane covered with a gold layer. This as sembly is supported by a silicon frame. By electron-beam patterning, i on milling and plasma etching, the Si3N4 and the gold are removed loca lly in 1 and 2 mu m-sized square windows. The microstructure of the re sulting free-standing foils, as studied with HRTEM, is polycrystalline with crystal sizes ranging from 3 to 15 nm. The foil thickness of 5 n m is confirmed by electron energy-loss spectroscopy. An application of such foils lies in the construction of a monochromatic high-brightnes s electron source, which is based on the ballistic transmission of ele ctrons through ultrathin foils, using the work function of the foil as an energy filter. (C) 1998 Elsevier Science B.V. All nights reserved.