DE2725885

A reactive sputtering process is described for producing a thin film of sputtered material on a tubular substrate which may, for example, be a solar collector tube. Uniformity of the composition of the sputtered layer at all points at the same depth in the film is achieved by preventing the movement of reactive gases through which the sputtering has already taken place, from one part of the zone of sputtering to another. In one way of achieving this result the reactive gas is swept from the zone of sputtering by entraining it in a gas stream flowing across the sputtering path. In an alternative way of achieving this result the rate of flow of reactive gas is finely controlled so that it is entirely consumed in one discrete area of sputtering so that there are no components of the reactive gas remaining which are free to move to other parts of the zone of sputtering and thereby change the atmospheric conditions in it. Apparatus for carrying out these two functions is described and utilizes tubes, which may be electrodes, formed with lines of holes or openings extending parallel to the axis of the tubular substrate on which the sputtered film is to be formed.