Low Energy Electron Transmission Through Thin Polymer Films

Extract

While transmission and beam damage have been well documented in the TEM at high accelerating potentials, considerably less is known about these phenomena at lower accelerating potentials. Imaging using low accelerating potentials may be attractive as an analytic technique, because chemical degradation associated with electron beam irradiation in organic macromolecules may be a function of accelerating potential (e.g. 1, 2). The present work examines low-energy electron transmission through thin polymer films and beam damage produced by low energy (∼ 0.5-10 keV) electrons.

Thin films of polystyrene were prepared by allowing a ∼ 0.005% solution of G3-5k arborescent polystyrene in toluene to evaporate on a holey carbon film. In solution, this arborescent polystyrene consists of spherical molecules of order 45 nm in diameter (3). When evaporated from dilute solution on a holey carbon film, monolayer thick self-assembled membranes form in some of the holes (figs. 1 and 2). The resulting films are highly reproducible in thickness and have a relatively uniform morphology (fig. 3).