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The adhesion of Au, Cu and Al films of thickness from 0·05 to 40 μm to glass and MgO single-crystal substrates was measured by a tangential shear test. For films deposited mainly at 10−7 to 10−8 Torr, the shear stress was found to be virtually independent of the film thickness, and had mean values of 3×105 N m−2 for Au, 8×105 N m−2 for Cu and 1·5×106 N m−2 for Al, for films on glass; these were increased by a factor of three for MgO substrates except for Al, for which the adhesion remained unaltered.These values are about 100 times smaller than those obtained in measurements where the force is applied normal to the substrate.Optical and Stereoscan micrographs indicate the basic features of the torn films after shear, in particular the formation of regularly shaped triangular tears in areas adjoining the adhesive junction, and the apical angle is found to vary systematically with the film thickness.

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