## 3 Results
Figure 3: FIB cross section of the debris zone of RMF structured at 100 fs at 1 kHz. (**a**) Overview of the cross section; (**b**) detail of the left end at the cut edge. The presence of the undamaged InCuSil layer indicates that direct ablation did not take place. The debris has a low density and a maximum thickness of 4.85 μm. Figure 2: Top-view SEM micrographs of single lines cut by DLW for the different samples (laser entry side): (**a**) 100 fs_1 kHz; (**b**) 150 fs_1 kHz; (**c**) 150 fs_5 kHz. The spot sizes and the total extension of debris are highlighted. (**d**) EDS spectra of the debris and the unstructured reference sample. Curves are offset by a fixed amount to improve visibility. TEM samples were taken perpendicular to the sample surface for all three laser parameters. Figure 4a-c shows SEM images of the thinned samples in the region of the cut edge, and the multilayer structure can be clearly recognized. A relatively compact layer of oxide covers the laser cut zone despite the cleaning process. This is in strong contrast to the thin and flaky surface debris. Higher magnification STEM-in-SEM images (Figure 4d-f) reveal a thin mixed metal zone of \(<\)100 nm between the multilayer and the oxide. Bright inclusions in the oxide appear to be trapped metallic droplets. The samples were then investigated through TEM to obtain more information on the mixing zone. For reference, the unaffected multilayer away from the cut edge was investigated first. Figure 5a shows a bright field image of the layer structure. It can be seen that the layers are not perfectly flat, and areas without clear separation of the layers can be recognized. Two ROIs from which SAD images were taken are indicated. The SAD taken from the large ROI1 is shown in (b). Diffraction rings are clearly visible, and the slightly inhomogeneous intensity distribution within each ring indicates crystallographic texture due to the growth process. Another SAD image was taken from an area of disturbed layer structure (ROI2) with the smallest available aperture of 180 nm diameter (Figure 5c). The measured d-spacings from both ROIs are summarized in Figure 5d. Although the layers in ROI2 appear much less clearly separated, all diffraction rings can be assigned to the pure elements Ni and Al, as is the case for ROI1. No intermetallic phases could be determined, which indicates that the perturbed appearance in ROI2 is due to projection artifacts rather than actual intermixing in the as-received state. TEM images at higher magnification indicate that only a small region of mixed metals exists at the cut edge. Unfortunately, this is thinner than the smallest aperture for selected area diffraction. Nevertheless, SAD images in various edge regions of the three different laser parameters were recorded. Indexing the reflections proved to be challenging due to the presence of Ni, Al, at least one mixed metal phase, and potentially some oxide in the diffracting volume. No SAD images could be indexed with just Ni, Al, and one single Ni-Al intermetallic phase alone. Since the SAD results were inconclusive, they are not shown here for the sake of brevity. Instead, distribution of the elements Ni, Al, and O was mapped with EELS. It is worth mentioning that a diverse range of shapes was observed at  
Figure 4: Top row: secondary electron SEM images of TEM samples taken from the laser cut edge of ultrasonically cleaned samples; (**a**) 100 fs_1 kHz, (**b**) 150 fs_1 kHz, (**c**) 150 fs_5 kHz. The original layer structure appears to be preserved up to a few hundred nm from the cut edge. Bottom row: STEM-in-SEM bright field images of samples (**d**) 100 fs_1 kHz, (**e**) 150 fs_1 kHz, and (**f**) 150 fs_5 kHz. A thin mixing zone between the layers and the oxide can be seen. the laser cut edge across all three samples, and no significant distinction could be made. Therefore, a detailed description of EELS mappings for only one of the samples is provided. Figure 6 shows the corresponding mappings of sample 100 fs_1 kHz.