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Tuning of strain and surface roughness of porous silicon layers for higher-quality seeds for epitaxial growth.

Karim M, Martini R, Radhakrishnan HS, van Nieuwenhuysen K, Depauw V, Ramadan W, Gordon I, Poortmans J - Nanoscale Res Lett (2014)

Bottom Line: We also found that if higher seed thickness and longer annealing time are to be preferred to minimize the strain in double layers, the opposite is required to achieve smoother layers.The impact of these two parameters may be explained by considering the morphological evolution of the pores upon sintering and, in particular, the disappearance of interconnections between the porous seed and the bulk as well as the enlargement of pores near the surface.An optimum epitaxial growth hence calls for a trade-off in seed thickness and annealing time, between minimum-strained layers and rougher surfaces. 81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties; 81.05.Rm Porous materials; granular materials; 82.80.Ej X-ray, Mössbauer and other γ-ray spectroscopic analysis methods.

View Article: PubMed Central - HTML - PubMed

Affiliation: KACST-Intel Consortium Center of Excellence in Nano-manufacturing Applications (CENA), Riyadh 11442, KSA ; Interuniversity Microelectronics Center (IMEC), Kapeldreef 75, Leuven 3001, Belgium ; Physics Department, Faculty of Science, Alexandria University, Alexandria 21511, Egypt ; Department of Electrical Engineering, KU Leuven, Leuven 3000, Belgium.

ABSTRACT

Unlabelled: Sintered porous silicon is a well-known seed for homo-epitaxy that enables fabricating transferrable monocrystalline foils. The crystalline quality of these foils depends on the surface roughness and the strain of this porous seed, which should both be minimized. In order to provide guidelines for an optimum foil growth, we present a systematic investigation of the impact of the thickness of this seed and of its sintering time prior to epitaxial growth on strain and surface roughness. Strain and surface roughness were monitored in monolayers and double layers with different porosities as a function of seed thickness and of sintering time by high-resolution X-ray diffraction and profilometry, respectively. Unexpectedly, we found that strain in double and monolayers evolves in opposite ways with respect to layer thickness. This suggests that an interaction between layers in multiple stacks is to be considered. We also found that if higher seed thickness and longer annealing time are to be preferred to minimize the strain in double layers, the opposite is required to achieve smoother layers. The impact of these two parameters may be explained by considering the morphological evolution of the pores upon sintering and, in particular, the disappearance of interconnections between the porous seed and the bulk as well as the enlargement of pores near the surface. An optimum epitaxial growth hence calls for a trade-off in seed thickness and annealing time, between minimum-strained layers and rougher surfaces.

Pacs codes: 81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties; 81.05.Rm Porous materials; granular materials; 82.80.Ej X-ray, Mössbauer and other γ-ray spectroscopic analysis methods.

No MeSH data available.


Related in: MedlinePlus

XRD profiles of annealed double layers of PSi with cross-sectional SEM images of different annealing times (1, 5, 10 and 30 min). The PSi-peak shift toward the Si-peak suggests a decrease of strain with annealing time that may be correlated with the disappearance of pillars in the HPL.
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Figure 7: XRD profiles of annealed double layers of PSi with cross-sectional SEM images of different annealing times (1, 5, 10 and 30 min). The PSi-peak shift toward the Si-peak suggests a decrease of strain with annealing time that may be correlated with the disappearance of pillars in the HPL.

Mentions: After monitoring as-etched double layers, the effect of annealing time on the strain and surface roughness was investigated on stacks with a fixed LPL and HPL, as listed in Table 1 (column “Impact of annealing time”). Figure 7 shows XRD profiles of the annealed double layer of PSi. Similarly to the case of PSi monolayers, the strain switches from tensile to compressive after annealing. Furthermore, the angular splitting of the XRD peaks decreases as the annealing time of the double layer of PSi increases over the investigated range. This indicates a ~37% incremental decrease in the out-of-plane compressive strain from 1.9 × 10−4 to 1.2 × 10−4, as shown in Figure 8. Finally, a thicker-LPL stack shows a lower strain than a thinner-LPL stack, as shown in Figure 8 with two LPL of 750- and 1,300-nm thickness.


Tuning of strain and surface roughness of porous silicon layers for higher-quality seeds for epitaxial growth.

Karim M, Martini R, Radhakrishnan HS, van Nieuwenhuysen K, Depauw V, Ramadan W, Gordon I, Poortmans J - Nanoscale Res Lett (2014)

XRD profiles of annealed double layers of PSi with cross-sectional SEM images of different annealing times (1, 5, 10 and 30 min). The PSi-peak shift toward the Si-peak suggests a decrease of strain with annealing time that may be correlated with the disappearance of pillars in the HPL.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128828&req=5

Figure 7: XRD profiles of annealed double layers of PSi with cross-sectional SEM images of different annealing times (1, 5, 10 and 30 min). The PSi-peak shift toward the Si-peak suggests a decrease of strain with annealing time that may be correlated with the disappearance of pillars in the HPL.
Mentions: After monitoring as-etched double layers, the effect of annealing time on the strain and surface roughness was investigated on stacks with a fixed LPL and HPL, as listed in Table 1 (column “Impact of annealing time”). Figure 7 shows XRD profiles of the annealed double layer of PSi. Similarly to the case of PSi monolayers, the strain switches from tensile to compressive after annealing. Furthermore, the angular splitting of the XRD peaks decreases as the annealing time of the double layer of PSi increases over the investigated range. This indicates a ~37% incremental decrease in the out-of-plane compressive strain from 1.9 × 10−4 to 1.2 × 10−4, as shown in Figure 8. Finally, a thicker-LPL stack shows a lower strain than a thinner-LPL stack, as shown in Figure 8 with two LPL of 750- and 1,300-nm thickness.

Bottom Line: We also found that if higher seed thickness and longer annealing time are to be preferred to minimize the strain in double layers, the opposite is required to achieve smoother layers.The impact of these two parameters may be explained by considering the morphological evolution of the pores upon sintering and, in particular, the disappearance of interconnections between the porous seed and the bulk as well as the enlargement of pores near the surface.An optimum epitaxial growth hence calls for a trade-off in seed thickness and annealing time, between minimum-strained layers and rougher surfaces. 81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties; 81.05.Rm Porous materials; granular materials; 82.80.Ej X-ray, Mössbauer and other γ-ray spectroscopic analysis methods.

View Article: PubMed Central - HTML - PubMed

Affiliation: KACST-Intel Consortium Center of Excellence in Nano-manufacturing Applications (CENA), Riyadh 11442, KSA ; Interuniversity Microelectronics Center (IMEC), Kapeldreef 75, Leuven 3001, Belgium ; Physics Department, Faculty of Science, Alexandria University, Alexandria 21511, Egypt ; Department of Electrical Engineering, KU Leuven, Leuven 3000, Belgium.

ABSTRACT

Unlabelled: Sintered porous silicon is a well-known seed for homo-epitaxy that enables fabricating transferrable monocrystalline foils. The crystalline quality of these foils depends on the surface roughness and the strain of this porous seed, which should both be minimized. In order to provide guidelines for an optimum foil growth, we present a systematic investigation of the impact of the thickness of this seed and of its sintering time prior to epitaxial growth on strain and surface roughness. Strain and surface roughness were monitored in monolayers and double layers with different porosities as a function of seed thickness and of sintering time by high-resolution X-ray diffraction and profilometry, respectively. Unexpectedly, we found that strain in double and monolayers evolves in opposite ways with respect to layer thickness. This suggests that an interaction between layers in multiple stacks is to be considered. We also found that if higher seed thickness and longer annealing time are to be preferred to minimize the strain in double layers, the opposite is required to achieve smoother layers. The impact of these two parameters may be explained by considering the morphological evolution of the pores upon sintering and, in particular, the disappearance of interconnections between the porous seed and the bulk as well as the enlargement of pores near the surface. An optimum epitaxial growth hence calls for a trade-off in seed thickness and annealing time, between minimum-strained layers and rougher surfaces.

Pacs codes: 81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties; 81.05.Rm Porous materials; granular materials; 82.80.Ej X-ray, Mössbauer and other γ-ray spectroscopic analysis methods.

No MeSH data available.


Related in: MedlinePlus