Density determination of nano-layers depending to the thickness by non-destructive method

Non-destructive tests used to characterize and observe the state of the solids near the surface or at depth, without damaging them or damaging them. Density is frequently used to follow the variations of the physical structure of the samples, as well as in the calculation of quantity of material required to fill a given volume, and it is also used to determine the homogeneity of a sample. However, the measurement of the acoustic properties (density, elastic constants,…) of a thin film whose thickness is smaller than several atomic layers is not easy to perform. For that reason, we expose in this work the effects of the thicknesses of thin films on the evolution of the density, where several samples are analyzed. The samples selected structures are thin films deposited on substrates, these coatings have thicknesses varying from a few atomic layers to ten or so micrometers and can change the properties of the substrate on which they are deposited. To do so, we considered a great number of layers (Cr, Al, SiO2, ZnO, Cu, AlN, Si3N4, SiC) deposited on different substrates (Al2O3, Cu and Quartz). It is first shown that the density exhibits a dispersive behaviour. Such a behaviour is characterized by an initial increase (or decrease) followed by a saturated region. Further investigations of these dependences led to the determination of a semi-empirical universal relations, ρ=f(h/λT), for all the investigated layer/substrate combination. Such expression could be of great importance in the density prediction of even layers thicknesses