## 3 Results
### Characterization of the Microstructure after RTA  
Both 3D-RMS on silicon needles and standard RMS on flat silicon were treated by rapid thermal annealing at 550 \({}^{\circ}\)C. During the process the heat radiation was used to initiate the phase transformation by solid diffusion. The multilayers deposited on flat Si after RTA peeled off from the substrate; however, the 3D-RMS remained attached to the substrate, this effect was already observed in previous investigations demonstrating the improvement in the adhesion of multilayers on silicon needles [18]. In order to verify the influence of the structure on the phase transformation, XRD analysis was performed. Figure 6 depicts the XRD patterns of both systems before and after RTA. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \(d\) & & \multicolumn{3}{c}{\(k\) (1/\(\upmu\)m)} & \multicolumn{6}{c}{\(k_{v}\) (\%)} \\ \hline  & & **1** & **2** & **3** & **4** & **1** & **2** & **3** & **4** & **Mean** & **SD** \\ \hline _ki_ & 0.17 & 15.55 & 5.18 & 12.19 & 9.00 & 100 & 100 & 100 & 100 & 100 & 0 \\ _kf\({}_{1}\)_ & 0.62 & 5.09 & 1.91 & 4.56 & 4.51 & 32.5 & 36.8 & 37.4 & 50.1 & 39.3 & 7.518 \\ _kf\({}_{2}\)_ & 1.37 & 2.57 & 1.42 & 2.24 & 2.51 & 16.6 & 27.4 & 18.4 & 27.85 & 22.5 & 5.907 \\ _kf\({}_{3}\)_ & 1.97 & 2.06 & 1.14 & 1.77 & 1.63 & 13.3 & 21.9 & 14.5 & 18.1 & 16.9 & 3.805 \\ _kf\({}_{4}\)_ & 2.20 & 1.80 & 1.02 & 1.29 & 1.36 & 11.6 & 19.8 & 10.6 & 15.1 & 14.3 & 4.163 \\ _kf\({}_{5}\)_ & 2.97 & 1.41 & 0.86 & 1.17 & 1.22 & 9.1 & 16.5 & 9.6 & 13.6 & 12.2 & 3.499 \\ _kf\({}_{6}\)_ & 3.48 & 1.33 & 0.74 & 1.09 & 1.07 & 8.6 & 14.2 & 8.97 & 11.9 & 10.9 & 2.620 \\ _kf\({}_{7}\)_ & 4.28 & 1.27 & 0.67 & 1.01 & 0.97 & 11.9 & 12.9 & 8.2 & 10.8 & 10.9 & 2.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Curvature measurements made at various distances \(d\) from the tip of the needle in different domains; \(k_{v}\) values were obtained following Equation (2). As deposited, in both systems the XRD patterns are similar, showing the peaks corresponding to the parent materials of Al fcc (PDF 02-004-0787) and Ni fcc (PDF 02-004-0850), where the peaks of Al (111) and Ni (200) are evident. It is also possible to observe the peaks of Si (PDF 02-027-1402), in the case of the flat Si the peak of (111) and in the case of Si needles the peak of (004). After the heat treatment, the peaks of Ni and Al disappear and the peaks corresponding to the B2 phase Al\({}_{0.42}\)Ni\({}_{0.58}\) (PDF 02-044-1267) are present. However, a different pattern is observed in the case of the 3D-RMS after RTA, which exhibits, in addition to the peaks corresponding to B2 phase Al\({}_{0.42}\)Ni\({}_{0.58}\), the peaks of the AlNi\({}_{3}\) phase (PDF 02-065-0144) [29]. The presence of this phase was already observed in multilayers with an excess of nickel in the atomic composition [30], and also near to the interface when the diffusion was not completed [31]. In the micrograph after RTA (Figure 7c,d), in the perpendicular section it is possible to see the traces of the multilayers, which indicates the presence of two phases (Figure 7c). However, in deeper layers, in the perpendicular section close to the Si needles, the layers are diffuse, which could indicate complete diffusion in this area. In order to reveal the phases formed in different areas of the domain, SAED analysis was carried out. Figure 6: XRD diffraction patterns of 3D-RMS before and after RTA compared with standard RMS after RTA. Figure 7: Scanning electron microscope of the 3D-RMS in a cross-section view for the as-deposited RMS (**a**,**b**) and after treatment with the RTA (**c**,**d**) up to 550 \({}^{\circ}\)C (the images were taken at the following tilt angles: (**a**) at 0\({}^{\circ}\), (**b–d**) at 51\({}^{\circ}\) and (**c**) at 53\({}^{\circ}\)). The insets display the diffraction contrast images of the respective picture (**a–d**). The diffraction rings are indexed to certain planes and phases in every inset.