RADIUS INCHES

For most applications of thin films, uniformity of film thickness over the substrate area is a necessary require-ment. An investigation is being carried out in the laboratory to obtain uniform films on optical com-ponents. During the course of investigation, i t was observed that reported values of geometrical parameters assumed for minimum variation in film thickness, based on the equation derived by Holland and Steckelmacher,' differ widely. Film thickness distribution curves pre-sented by R4acleod2 are found to be in error. The corrected distribution curves are presented. Also the thickness distribution curves are presented in a form in which suitable geometrical parameters can be chosen readily to yield the desired uniformity in thickness over the area of the substrate. For a small area surface source the distribution of film thickness on a planar substrate is given by m h2 (h2 + p2 + R2) (1) t = -. ~p [ (h2 +p2 +R2) '- 4p2R2])&apos