## 4 Results and Discussions
### Material and Crystal Properties
According to the measured Raman spectra (right-side graph), this area is mainly in the micro-Si phase (as indicated by the flash arrow labelled \"micro-Si\"). Inside this mico-Si layer, there are several dark disk areas, marked by yellow rings, with approximate outer diameters of 70-100 \(\upmu\)m and inner diameters of 20-30 \(\upmu\)m. Based on the measured Raman spectra, these areas  
Figure 6: Optical micrograph of the CuIC micro-Si thin film with (glass/p-type Si/Cu) structure after annealing at 550 \({}^{\circ}\)C.  
Figure 7: Optical micrograph of the CuIC micro-Si thin film with (glass/p-type Si/Cu) structure after annealing at 750 \({}^{\circ}\)C (the scale bar is 50 \(\upmu\)m). had crystallized yet, and were probably composed of mixture of a- and nano-Si phases. In the center of each disk, there is a small bright area surrounded by the inner circle, which was likely composed of the nano-Si phase. This area is increased in size (and the corresponding ring became narrower) as the crystallization process progressed, either by extending the annealing time or increasing the annealing temperature. Figure 8 shows the surface of another sample annealed at 950 \({}^{\circ}\)C. At such a high temperature, several large crystallized areas with dimensions of 10-50 \(\upmu\)m were created; their dendrite shapes are clearly observable (as indicated by red ovals). However, the created layer is no longer continuous, perhaps due to the low thickness of the deposited film. As mentioned before, at this high temperature, crystal growth happens in different orientations; this could be another reason for the poor quality of the thin film after annealing at 950 \({}^{\circ}\)C.  
In the next step, the surface of the fabricated films was studied by SEM microscopy in order to gain a better insight into the nano- and micro- structures of the crystallized Si layer. The micrograph of the deposited (n-type C-Si/p-type micro-Si/Cu) film structure after annealing at 500 \({}^{\circ}\)C is shown in Figure 9a. According to this micrograph, the majority of the film surface was covered by a uniform mixture of Cu and Si in amorphous and nano-crystalline phases (e.g., the area labeled \"a\"). The brighter spots are likely the clusters of copper (indicated by \"b\") formed on the mixture (a + nano) of the phases of Si and Cu. This SEM image confirms the previous results that indicate the very low crystallization ratio of the film at low temperatures. Figure 9b displays the SEM of a sample annealed at 600 \({}^{\circ}\)C, which shows different crystallization conditions in comparison to the former sample. A fine and almost uniform layer which is still not fully crystallized formed in the background of the images. However, several dark areas are distinguishable, defined by yellow contours and labelled \"c\"; these are likely composed of the nano- and micro-Si phases which resulted from the applied thermal treatments. The residual bulk of Cu which did not contribute to the CuIC process is seen as bright spots (due to the SEM imaging nature) and was labelled \"b\". This SEM image confirms a small grain size i.e., \(\sim\)20 nm, as determined by XRD measurement, shown in the graph of Figure 5b. Figure 8: Optical micrograph of the CuIC micro-Si thin film with (glass/p-type Si/Cu) structure after annealing at 950 \({}^{\circ}\)C.