Thermal stability of the Cu/Ni multilayer system in X-ray diffraction and scanning microscopy examinations

The article presents the results of research into the effect of heating on the stability of a Cu/Ni multilayer applied onto a Si(100) substrate by the magnetron sputtering method. The multilayer was heated in a furnace atmosphere in a temperature range of 40-230 degrees C. The X-ray structural examination by the X-ray diffraction (XRD) and the grazing X-ray incidence diffraction (GIXRD) methods and microscopic observations of the multilayer surface were carried out. Structural changes were found to occur under the influence of heating due to the mutual diffusion of Cu and Ni, resulting in a loss of the multilayer nature of the structure. Early indications of a surface discontinuity of the multilayer, as noticed in microscopic observations and then confirmed by X-ray measurements, were found at a temperature of 220 degrees C. At higher temperatures, intensive delamination of the multilayer from the silicon substrate followed as a result of thermal stresses caused by a large difference in the thermal expansion coefficients between the multilayer and silicon.