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Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers.

Frigeri C, Serényi M, Khánh NQ, Csik A, Riesz F, Erdélyi Z, Nasi L, Beke DL, Boyen HG - Nanoscale Res Lett (2011)

Bottom Line: Hydrogenated multilayers (MLs) of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation.Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice.This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMEM Institute, Parco Area delle Scienze 37/A, 43100 Parma, Italy. frigeri@imem.cnr.it.

ABSTRACT
Hydrogenated multilayers (MLs) of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation. Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice. This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers.

No MeSH data available.


Related in: MedlinePlus

IR absorbance spectra in the stretching mode range of the wave number for a-Si/a-Ge MLs sputtered under H flow rate of 0.8 ml/min. B1 is the spectrum of the as-deposited layer, B2 the spectrum after annealing at 400°C for 1 h and B3 the one after annealing at 400°C for 10 h.
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Figure 3: IR absorbance spectra in the stretching mode range of the wave number for a-Si/a-Ge MLs sputtered under H flow rate of 0.8 ml/min. B1 is the spectrum of the as-deposited layer, B2 the spectrum after annealing at 400°C for 1 h and B3 the one after annealing at 400°C for 10 h.

Mentions: A typical set of IR absorbance spectra in the stretching mode range of the wave number is shown in Figure 3. The spectra refer to MLs hydrogenated with a H flow rate of 0.8 ml/min: B1 is the spectrum of the as-deposited layer, B2 the spectrum of the ML annealed at 400°C for 1 h and B3 the one of the sample annealed at 400°C for 10 h. Spectrum B1 shows the peaks at 1880 and at 2010 cm-1, which are the fingerprints of the monohydride bonds of H to Ge and Si, respectively [10,18-20]. The shape of the Si-H peak indicates that the peak of the Si di-hydride bond, Si-H2, at about 2140 cm-1 could also exist hidden in the tail of the Si-H peak at high wave numbers. The shift with respect to the standard value of 2100 cm-1 can be due to the presence of (Si-H2)n poly-hydrides [10,18] or to a possible contamination of the hydrides by oxygen [18]. The latter contamination, if any, may come from oxygen residues in the sputtering chamber. The presence of the Ge di-hydride on the high wave number side of the Ge-H peak is not certain. The possible existence of Si-H2 bonds could be suggested by spectrum B2 also showing a peak around 2140 cm-1. Figure 3 shows that, upon annealing, the Si-H and Ge-H bonds break with consequent release of H. H has totally been released from Ge already after 1 h annealing, while it still remains somewhat bound to Si as mono- and di-hydride. After 10 h annealing, H is totally released from Si as well.


Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers.

Frigeri C, Serényi M, Khánh NQ, Csik A, Riesz F, Erdélyi Z, Nasi L, Beke DL, Boyen HG - Nanoscale Res Lett (2011)

IR absorbance spectra in the stretching mode range of the wave number for a-Si/a-Ge MLs sputtered under H flow rate of 0.8 ml/min. B1 is the spectrum of the as-deposited layer, B2 the spectrum after annealing at 400°C for 1 h and B3 the one after annealing at 400°C for 10 h.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211242&req=5

Figure 3: IR absorbance spectra in the stretching mode range of the wave number for a-Si/a-Ge MLs sputtered under H flow rate of 0.8 ml/min. B1 is the spectrum of the as-deposited layer, B2 the spectrum after annealing at 400°C for 1 h and B3 the one after annealing at 400°C for 10 h.
Mentions: A typical set of IR absorbance spectra in the stretching mode range of the wave number is shown in Figure 3. The spectra refer to MLs hydrogenated with a H flow rate of 0.8 ml/min: B1 is the spectrum of the as-deposited layer, B2 the spectrum of the ML annealed at 400°C for 1 h and B3 the one of the sample annealed at 400°C for 10 h. Spectrum B1 shows the peaks at 1880 and at 2010 cm-1, which are the fingerprints of the monohydride bonds of H to Ge and Si, respectively [10,18-20]. The shape of the Si-H peak indicates that the peak of the Si di-hydride bond, Si-H2, at about 2140 cm-1 could also exist hidden in the tail of the Si-H peak at high wave numbers. The shift with respect to the standard value of 2100 cm-1 can be due to the presence of (Si-H2)n poly-hydrides [10,18] or to a possible contamination of the hydrides by oxygen [18]. The latter contamination, if any, may come from oxygen residues in the sputtering chamber. The presence of the Ge di-hydride on the high wave number side of the Ge-H peak is not certain. The possible existence of Si-H2 bonds could be suggested by spectrum B2 also showing a peak around 2140 cm-1. Figure 3 shows that, upon annealing, the Si-H and Ge-H bonds break with consequent release of H. H has totally been released from Ge already after 1 h annealing, while it still remains somewhat bound to Si as mono- and di-hydride. After 10 h annealing, H is totally released from Si as well.

Bottom Line: Hydrogenated multilayers (MLs) of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation.Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice.This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNR-IMEM Institute, Parco Area delle Scienze 37/A, 43100 Parma, Italy. frigeri@imem.cnr.it.

ABSTRACT
Hydrogenated multilayers (MLs) of a-Si/a-Ge have been analysed to establish the reasons of H release during annealing that has been seen to bring about structural modifications even up to well-detectable surface degradation. Analyses carried out on single layers of a-Si and a-Ge show that H is released from its bond to the host lattice atom and that it escapes from the layer much more efficiently in a-Ge than in a-Si because of the smaller binding energy of the H-Ge bond and probably of a greater weakness of the Ge lattice. This should support the previous hypothesis that the structural degradation of a-Si/a-Ge MLs primary starts with the formation of H bubbles in the Ge layers.

No MeSH data available.


Related in: MedlinePlus