Abstract
Tensile tests were carried out for copper thin films. Three kinds of thin films were fabricated by RF magnetron sputtering. The target power was changed from 10 to 100 W to control the grain size. The grain size increased with increasing target power. The effect of grain size on the deformation behavior under tensile loading was investigated by X-ray method. The residual compressive stress determined by X-ray method increased with increasing grain size. On the other hand, the 0.2% proof stress decreased with grain size. The relation between the applied stress and the X-ray stress can be divided into four regions. In the first region, the X-ray stress increased linearly with applied strain. In the second region, the value of the full width at half maximum, FWHM, increased rapidly with applied strain. Then the stress became constant in the third region. In the final region, the stress and FWHM decreased with applied strain. During unloading, the value of FWHM decreased with stress. For the specimen with fine grains, when the stress became zero, the value of FWHM decreased to an initial value in spite of large plastic deformation. After tensile loading, many intergranular cracks could be observed on the specimen surface. Decrease of the stress and FWHM in the final region comes from the nucleated cracks.
