Production of Carbon Films for Electron Microscopy; Hydrofluoric Acid Detachment from Glass

Abstract

Chemically clean microscope slides are coated as usual by vaporized carbon. The carbon film is floated off the slide by slowly lowering it at an angle of 45° into 1% HF in distilled water containing 0.025% Tween 80. This solution fills completely (forming a positive meniscus at the edges) one chamber of a double-compartment Perspex trough; the other compartment being similarly filled with the Tween solution only. A Teflon bar, laid on top of the partition keeps the solutions from mixing. After the carbon film loosens, it is floated across the central partition into the second compartment with the aid of a second Teflon bar, using both bars to guide the film on the surface of the fluid. The HF is thus washed from the film. Grids are thinly coated with 0.5% poly isobutylene in toluene (as an adhesive) and previously placed on a rectangle of filter paper supported by wire screening about 1/2 inch from the bottom of the trough. While the Tween solution is drained away through a bottom opening, the carbon film is guided to cover the grids. The filter paper bearing the grids is then removed and caused to dry slowly (about 12-16 hr) to avoid cracking or distortion of the film.