Tensile Properties of Thin, Evaporated Gold Films

Evaporated gold films in the 500–15 000 A thickness range were prepared on rocksalt substrates. Depending on the temperature of the substrate during deposition, the films were completely, partially, or randomly oriented with respect to the (100) plane of the rocksalt, as determined by x-ray diffraction. The stress-strain curve of the free films was investigated and was found to be quite steep up to very high stresses, but plastic deformation and creep were observed even at relatively low stresses. The ultimate tensile strength of the films is from 2 to 4 times that of the annealed bulk material and is not a function of film thickness. The Young's moduli are found to be normal. Comparing the stress-strain behavior of evaporated films with that of whiskers suggests that the former owe their high strength to a high concentration of defects which were uniformly quenched in during the evaporation process, and which greatly impede dislocation motion and multiplication, and not to an abnormally high stress required to nucleate dislocations which is commonly observed in whiskers.