Fig. 1. The microstructures of as-deposited Ni/Mo multilayers: (a) bright-field and (b) dark-field images of cross-sectional multilayers, (c) the corresponding selected area diffraction pattern.

Fig. 2. XRD patterns of as-deposited Ni/Mo multilayers upon annealing.

Fig. 3. TEM images of Ni/Mo interface of as-deposited (a1) and 500 °C annealed (b1) multilayers, HRTEM images of the GB wetting (denoted as green dash lines) at the Ni/Mo interface of as-deposited (a2) and 500 °C annealed (b2) multilayers, and amorphous Mo regions (denoted as yellow dot lines) of the corresponding Ni/Mo interface (denoted by white dot lines in (b1) and (b2)) of as-deposited (a3) and 500 °C annealed (b3) multilayers. The observation areas are both taken at the interface between the third Ni layer and third Mo layer counted from the substrate.

Fig. 4. (a) STEM images of cross-sectional Ni/Mo multilayers annealed at 500 °C, (b) the corresponding EDX element mappings of the GB wetting (denoted by green dash lines). The observation area is taken at the interface between the third Ni layer and the third Mo layer counted from the substrate.

Fig. 5. The hardness and modulus of as-deposited and annealed Ni/Mo multilayers.

Fig. 6. Plots of lattice spacing as a function of $\text{si}{{\text{n}}^{2}}\psi $ in the as-deposited and annealed states for Ni sublayers (a) and Mo sublayers (b). The residual stresses are indicated from the slopes of the straight lines drawn through the data points. The strain-free directions are denoted by vertical dash lines in both figures.

Fig. 7. The thermodynamic driving force of the GB wetting of crystalline Mo (a) and amorphous Mo (b) in Ni GBs.