Speaker
Description
Nano-multilayers (NMLs) represent an important class of nano-architectured materials which find numerous applications in the fields of microelectronics, optics and sensing devices. The presence of (high) residual stress resulting from the multiple interfaces, epitaxy, grain boundaries and impurities gives rise to mechanical and thermal technological challenges in NMLs. Stability and performance at high temperatures can indeed be compromised. In particular, non uniform stress distribution across the depth play a major role for diffusion-controlled thermal grooving of grain boundaries at the base of nano-multilayer degradation [1].
In the present study, we investigate the strain variation across single layers of Cu and in Cu/W multilayers with different period thickness distribution across the depth. We performed an advanced laboratory-based in-plane grazing X-ray diffraction to access the in plane lattice parameters at different depths. Monte Carlo least squares minimization fit and the inverse Laplace matrix approach (linear system solution) were used to derive the lattice parameter depth profile starting from power expansion model and a Fourier series [2]. By varying the Cu/W bilayer thicknesses across the multilayer structure, we create a thickness strain gradient.The effect of the arrangement of different Cu/W bilayer blocks (3 nm Cu / 3 nm W and 10 nm Cu / 3 W nm bilayers) on the variation of microstructure and residual stresses upon the high-temperature thermal treatment in the range of 400-800 °C is investigated. The non monotonic W and Cu strain profiles across thickness are discussed in relation to their microstructure and thermal stability.
[1]F. Moszner et al., Acta Materialia 107, 345 (2016).
[2]C. Cancellieri et al. J. Appl. Cryst. 54, (2021).
| Speaker Country | Switzerland |
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