## 3 Results and Discussion
As can be seen, both the comb and the secondary prone are in the same orientation. From the color legend shown in Figure 6c, this orientation corresponds to [110] directions indicating that the growth is producing a face orientation as schemed in Figure 1c; the growth axis changes between the comb and the prone due to the different reactivity of the lateral faces exposed. Figure 4: SEM images of the structures grown on the samples with 10 wt% Li. (**a**) Ribbons grown onto the alumina boat, (**b**) Secondary prongs grown from the lateral faces of the comb-like structures and (**c**) filling of the spaces between the ribbons to form the final ribbon morphology. Figure 5: SEM images of the structures grown on the samples with 10%wt. Li. (**a**) panoramic view of the diversity of morphologies obtained in this case, (**b**) oriented small plates and (**c**) scheme of the growth model suggested. Compositional analysis of the structures was performed by EDX in the SEM. Although the percentage of dopants incorporated into the structures cannot be determined because Li is not detectable by the technique, EDX spectra recorded on the structures show the presence of Eu peaks. Furthermore, the compositional maps (Figure 7) also show that the Eu is homogeneously distributed throughout the structures. XRD measurements were performed on the structures grown in all samples. Figure 8 show the pattern obtained from the structures grown on the sample with 5 wt%. Li; as can be seen, all the diffraction peaks can be identified as the wurtzite phase of ZnO (JCPDS 00-036-1451), indicating the good crystallinity of the grown structures. No significant shifts in the positions of the reflections were observed when the Li content changed. Figure 6: EBSD analysis of the growth orientations of a comb-like structure. **(a)** Secondary electron image of a comb-like structure with secondary growth of a prone, the directions of the detector are fixed in the lower right corner, **(b)** Orientation map taken along the \(Z\) axis and **(c)** color legend used in the EBSD map. Figure 7: **(a)** SE image of a comb-like structure grown on the samples with 5 wt% of Li, and **(b)** corresponding EDX map of the distribution of Eu along the structure. Raman spectroscopy measurements show the most characteristic peaks of ZnO. In Figure 9, the Raman spectra from isolated rod-like structures, normalized to the 438 cm\({}^{-1}\) peak, are shown. The observed peaks correspond to the E\({}_{2}\)low and E\({}_{2}\)high of the wurtzite structure (98 and 438 cm\({}^{-1}\), respectively), although they are shifted with respect to the position in undoped ZnO [35]. To show this shift more clearly, a zoom of the 438 cm\({}^{-1}\) is shown in Figure 9b. Upon Eu doping, the peaks shift towards lower frequencies, which corresponds to the incorporation of a heavier atom. When Li is introduced, the peak moves back towards higher frequencies, although the original position of ZnO is not reached. In the spectra, a peak at 320 cm\({}^{-1}\) corresponding to A\({}_{1}\) mode (E\({}_{2}^{\text{high}}-\)E\({}_{2}^{\text{low}}\)) is also visible [35]. To study isolated structures, they are scratched from the pellet and deposited onto a Si substrate; the peak at 300 cm\({}^{-1}\) corresponds to the silicon substrate [36]. Cathodoluminescence (CL) spectra were recorded from isolated structures as well as from the pellet. To isolate the structures, we scratched them from the surface and deposited them onto a piece of graphite tape. The spectra from the pellet were recorded in areas in which no growth occurred. The results are shown in Figure 10. Part a of the figure show  
Figure 8: XRD pattern obtained from the structures grown on the sample with 5 wt% Li. The peaks with higher intensity are labeled. All the diffraction peaks correspond to reflections of the ZnO wurtzite structure (JCPDS 00-036-1451).