The structure and physical properties of thin films of metal on solid surfaces

Abstract

In spite of careful researches, extending over some fifty years, investigations on the colour and other optical properties, and on the electrical resistance of thin films of metal deposited on solid surfaces, have frequently led to uncertain and even contradictory results. These have been generally set down as due to variations, of an unspecified nature, in the structure. Direct work on the structure was, however, scanty until the last few years, when Professor G. P. Thomson and his school have obtained a number of valuable results, to which reference will be made later, by the application of the method of electron diffraction. This method tells us whether the film is amorphous or crystalline, and further gives information, if it is crystalline, as to the orientation of the axes and the spacing of the planes. The electron beam, however, examines an area of the order of a square millimetre, and the effect recorded is a statistical average for such a surface, and further the beam itself, with its inevitable heating effect, is liable to produce changes in the film. There is clearly room, then, for a detailed microscopic examination of the structure of sputtered films, which, as the following pages show, can furnish information as to local variations of structure which other methods cannot supply.