This work aims at tuning these parameters to minimize strain and surface roughness of the PSi stack which, in turn, affects the epitaxial growth and thus the presence of crystalline defects in the epitaxial foils. For monolayers of PSi, our results reveal that strain and surface roughness decrease by decreasing the thickness of the layer. A similar behavior was observed for as-etched monolayers and for annealed monolayers, but with higher absolute values and opposite sign. As expected, annealing has an effect of strain relief related to the morphological changes implied by the sintering. Moreover, surface roughness also increased with layer thickness. This was attributed this website to the bigger pore

formation at the top surfaces

of thicker PSi layers. Therefore, all PS 341 these results suggest that, both in terms of strain and surface roughness, thinner PSi layers would be better and highly preferred for high-quality epitaxial growth. However, for forming detachable epitaxial foils, a HPL is to be included below the seed layer. And, unexpectedly, strain decreased and saturated, by increasing the thickness of the LPL. We explained this by proposing to consider the interaction between the strain in the HPL and the LPL at their interface and that the dominating source of strain in the double layer of PSi is coming from the HPL. Also, our results reveal that strain is released gradually from double layers of PSi by longer annealing times. This was attributed to the disappearing of the inter-connections between the porous seed layer and the Si

substrate. The exposure to longer annealing times of the double layer of PSi results in fact in a lower density of pillars that, in turn, results in a lower out-of-plane compressive strain. TCL This check details interpretation was supported by measurements on samples with higher and lower porosity HPL, with higher and lower density of pillars, respectively. However, if longer annealing times result in lower strain, they may conversely result in a significant increase in surface roughness, due to the occasional opening of pores at the very top surface over time. Finally, for a multi-layer stack of PSi, which is a must to combine ease of foil detachment and good crystalline quality, thicker LPL and longer annealing times help in reducing strain but produce a rougher surfaces. A trade-off between these effects, of lower-strained stack and rougher seed, is required for finding the optimum condition for a better seed template for higher quality epitaxial growth. Further work will therefore focus on investigating directly the crystalline quality of epi-foils grown on seeds of various annealing times and thicknesses, in order to identify the dominating effects. Authors’ information MK is a joint PhD student at Alexandria University, Egypt, and KU Leuven, Belgium. RM is a PhD student at KU Leuven. HSR is a researcher in Silicon Photovoltaics at IMEC, Belgium.