Mechanical spectroscopy and structural evolution of CuMo thin films

CuMo thin films with a typical thickness of 200 nm have been prepared by Ion Beam Sputtering (IBS) on oxidised silicon (100) substrates. Two samples with symmetric (atomic) composition Cu30Mo70 and Cu70Mo30 where studied. ‘Direct’ observations of the microstructure were performed by X-ray diffraction. The samples have been characterised in their as-sputtered state, then after annealing at increasing temperature. On the other hand, a vibrating reed device specially adapted for thin adherent films has been used to determine the mechanical properties over a temperature range between 20°C and 500°C. In this paper, it is shown that the structural evolution in temperature highly depends on the sample composition. Particularly, in the Mo-rich specimen, two independent stages have been shown. Indeed, the segregation process is preceded by a structural relaxation phenomenon. We have also shown that internal friction experiments are quite useful in the study of these structural modifications occurring in thin films.