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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

RMS values of the LPL surfaces of the annealed PSi double layer. RMS values of surface roughness of the annealed double layer of PSi, with 750- and 1,300-nm thick LPL, as a function of annealing time (1, 5, 10 and 30 min). The roughness increases slightly from 1 to 10 min and becomes unstable for longer times.
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Figure 11: RMS values of the LPL surfaces of the annealed PSi double layer. RMS values of surface roughness of the annealed double layer of PSi, with 750- and 1,300-nm thick LPL, as a function of annealing time (1, 5, 10 and 30 min). The roughness increases slightly from 1 to 10 min and becomes unstable for longer times.

Mentions: To conclude on the impact of annealing time on the PSi stack, the surface roughness of the seed layer was also analyzed for two double porous silicon layers with LPL of 750- and 1,300-nm thickness. Figure 11 shows the RMS values of the LPL surfaces which vary slightly, and then show a sudden increase at longer annealing time for the thicker-LPL double stack. This observation may be understood in light of the fact that a longer annealing time results in formation of larger pores, which coarsen at the very top surface of the seed. Accordingly, large valleys (holes) may appear sporadically on the surface, which results in a rougher surface. Figure 12 shows the derivative of the bearing area curve (BAC) for the larger scanned area of the thicker-LPL sample. It was observed that there is no significant change in RMS roughness values between smaller (20 × 20 μm2) and larger (100 × 100 μm2) scanned areas. However, the increase of the non-symmetries of the graphs upon longer annealing times indicates an increase in the probability of the presence of holes. As the annealing time increases, the asymmetry of the curves is pushed toward the negative x-axis, which indicates the increased density of holes - as opposed to bumps - in the seed layer upon longer annealing.


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)

RMS values of the LPL surfaces of the annealed PSi double layer. RMS values of surface roughness of the annealed double layer of PSi, with 750- and 1,300-nm thick LPL, as a function of annealing time (1, 5, 10 and 30 min). The roughness increases slightly from 1 to 10 min and becomes unstable for longer times.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 11: RMS values of the LPL surfaces of the annealed PSi double layer. RMS values of surface roughness of the annealed double layer of PSi, with 750- and 1,300-nm thick LPL, as a function of annealing time (1, 5, 10 and 30 min). The roughness increases slightly from 1 to 10 min and becomes unstable for longer times.
Mentions: To conclude on the impact of annealing time on the PSi stack, the surface roughness of the seed layer was also analyzed for two double porous silicon layers with LPL of 750- and 1,300-nm thickness. Figure 11 shows the RMS values of the LPL surfaces which vary slightly, and then show a sudden increase at longer annealing time for the thicker-LPL double stack. This observation may be understood in light of the fact that a longer annealing time results in formation of larger pores, which coarsen at the very top surface of the seed. Accordingly, large valleys (holes) may appear sporadically on the surface, which results in a rougher surface. Figure 12 shows the derivative of the bearing area curve (BAC) for the larger scanned area of the thicker-LPL sample. It was observed that there is no significant change in RMS roughness values between smaller (20 × 20 μm2) and larger (100 × 100 μm2) scanned areas. However, the increase of the non-symmetries of the graphs upon longer annealing times indicates an increase in the probability of the presence of holes. As the annealing time increases, the asymmetry of the curves is pushed toward the negative x-axis, which indicates the increased density of holes - as opposed to bumps - in the seed layer upon longer annealing.

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