Tensile and compressive stresses in Cu/W multilayers: Correlation with microstructure, thermal stability, and thermal conductivity

The internal stress and microstructure in nanomultilayers strongly affect their reliability and performance, especially towards higher service temperatures. The initial stress and microstructure can be controlled during the growth by opportunely changing the deposition parameters. The intrinsic stress state can be tuned to achieve stress states ranging from compressive to tensile. In the present work, Cu/W nanomultilayers with opposite stress states (tensile and compressive) were fabricated by magnetron sputtering. The stress is found to be strongly correlated to the microstructure and internal disorder, as measured by X-ray diffraction and photoemission. In particular, higher disorder at the internal interfaces occurs in the presence of tensile growth stresses. The compressive nanomultilayers exhibit a more ordered structure, which improves their thermal stability up to 800 ∘C. The different microstructures for the opposite stress states significantly impact the thermal stability and thermal conductivity of the nanomultilayer stack. Our study thus sheds light on the correlations between the stress state, microstructure, thermal stability and thermal conductivity of Cu/W nanomultilayers.