## 3 Results and Discussion  
### Structural Properties  
#### 3.1.1 Transmission Electron Microscopy  
Figure 2 shows the cross section TEM images of coated films with red light-emitting Si-NCs before (A) and after (B) thermal annealing. Before annealing, a clear frontier between the crystalline Si-NCs and amorphous SOG layers can be observed. Conversely, the frontier between the amorphous and the crystalline regions is practically lost after thermal annealing. Furthermore, it is then possible to observe some amorphous barriers between the Si-NCs (white circle in the Figure 2B). This is probably because the thermal treatment promotes the flow of the SOG through the layer of the Si-NCs. The insets of Figure 2B(b) shows an FFT (Fast Fourier Transform) performed to the TEM images (Figure 2B(a)) in order to determine the distance between atomic layers of Si-NCs. The nanocrystal lattice spacing in high resolution transmission electron microscopy (HRTEM) images was estimated using the digital micrograph software (version 3.1.1, Gatan Inc., Pleasanton, CA, USA) to identify the orientation of the crystalline planes. The distances obtained correspond to the face-centered cubic lattice of crystalline silicon (joint committee on powder diffraction standards (JCPDS) #27-1402) (see inset Figure 2B(d)).  
Figure 1: Schemes for: (**a**) coated; and (**b**) embedded films with **red** or **blue** Si-NCs (silicon nanocrystals).  
Due to the nature of the coated films, it is not possible to observe the shape of Si-NCs. However, in the case of films with embedded red light-emitting Si-NCs (Figure 3A), it is possible to observe nearly spherical particles, as typically produced by the electrochemical technique [28]. The nanocrystals' diameter ranges from 1.5 nm to 4.5 nm with a mean size of 2.5 nm. In addition, a variety of crystalline planes corresponding to polycrystalline agglomerates was discovered, as observed in the inset Figure 3A(d).  
In the case of embedded films made with blue light-emitting Si-NCs, these cannot be clearly observed with the naked eye in the TEM images (Figure 3B(a)), making it difficult to select the area to perform the FFT analysis. However, some diffraction patterns can be observed after processing the TEM images, as shown in the inset Figure 3B(d). These diffraction patterns indicate crystalline silicon with cubic structure. This was confirmed with the X-ray measurements.  
Figure 3: Cross-section TEM images of embedded films with **red** (**A**) and **blue** (**B**) Si-NCs, after thermal annealing at 1100 \({}^{\circ}\)C for 3 h in N\({}_{2}\) atmosphere. In both images, the **white** square marks the area of analysis where there is a Si-NCs. The insets are: (**a**) the cross-section TEM images; (**b**) FFT; (**c**) the specific pattern of the **white** square area; and (**d**) the electrons’ diffraction planes of the **white** square areas, for each image.  
Figure 2: Cross-section TEM (transmission electron microscopy) images of coated films with **red** Si-NCs before (**A**) and after (**B**) thermal annealing at 1100 \({}^{\circ}\)C for 3 h in N\({}_{2}\) atmosphere. In both images, the **white** square marks the area of analysis where there are Si-NCs. The insets of (**B**) are: (**a**) cross-section TEM images; (**b**) FFT (Fast Fourier Transform); (**c**) the specific pattern of the **white** square area; and (**d**) the electrons diffraction planes of the **white** square area. The **white** circle in the Figure 2B shows a zone where the SOC (Spin on Glass) flowed around the Si-NC after annealing.