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Porous anodic alumina on galvanically grown PtSi layer for application in template-assisted Si nanowire growth.

Michelakaki I, Nassiopoulou AG, Stavrinidou E, Breza K, Frangis N - Nanoscale Res Lett (2011)

Bottom Line: We report on the fabrication and morphology/structural characterization of a porous anodic alumina (PAA)/PtSi nano-template for use as matrix in template-assisted Si nanowire growth on a Si substrate.The PtSi layer was formed by electroless deposition from an aqueous solution containing the metal salt and HF, while the PAA membrane by anodizing an Al film deposited on the PtSi layer.The morphology and structure of the PtSi layer and of the alumina membrane on top were studied by Scanning and High Resolution Transmission Electron Microscopies (SEM, HRTEM).

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microelectronics, NCSR Demokritos, Terma Patriarchou Grigoriou, Aghia Paraskevi, 153 10, Athens, Greece. A.Nassiopoulou@imel.demokritos.gr.

ABSTRACT
We report on the fabrication and morphology/structural characterization of a porous anodic alumina (PAA)/PtSi nano-template for use as matrix in template-assisted Si nanowire growth on a Si substrate. The PtSi layer was formed by electroless deposition from an aqueous solution containing the metal salt and HF, while the PAA membrane by anodizing an Al film deposited on the PtSi layer. The morphology and structure of the PtSi layer and of the alumina membrane on top were studied by Scanning and High Resolution Transmission Electron Microscopies (SEM, HRTEM). Cross sectional HRTEM images combined with electron diffraction (ED) were used to characterize the different interfaces between Si, PtSi and porous anodic alumina.

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Current-time anodization curves of an Al film on Si and on different PtSi/Si substrates (samples S-5 min, S-15 min, and S-30 min). In all cases, the Al film thickness was 500 nm. The anodization curve of sample Al/S-5 min is quite similar to that of Al/Si, while in the cases of samples Al/S-15 min and Al/S-30 min the current increases significantly when the PAA film reaches the underlying surface.
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Figure 5: Current-time anodization curves of an Al film on Si and on different PtSi/Si substrates (samples S-5 min, S-15 min, and S-30 min). In all cases, the Al film thickness was 500 nm. The anodization curve of sample Al/S-5 min is quite similar to that of Al/Si, while in the cases of samples Al/S-15 min and Al/S-30 min the current increases significantly when the PAA film reaches the underlying surface.

Mentions: Porous anodic alumina (PAA) can be grown on Si by anodic oxidation of an Al film. In this work, we investigated the formation of a PAA template on top of the PtSi layer with the objective to use the PtSi layer underneath as a catalyst for the formation of Si nanowires into the alumina pores. We used three of the PtSi films grown above, namely S-5 min, S-15 nm and S-30 min. An Al film, 500 nm thick, was deposited on the PtSi/Si substrate and an Al ohmic contact was formed on the backside of the wafer. The samples were then anodized in sulfuric acid aqueous solution at an anodization voltage of 20 V. The corresponding current-time anodization curves, compared to the one obtained without the PtSi layer, are shown in Figure 5. The general form of the curves is the same as that of the Al/Si anodization curve up to the time that the pores reach the Al2O3/Si or Al2O3/PtSi interface. The different phases of the anodization process are as follows [21]: At the very beginning of the anodization the current drops spontaneously to a lower value due to initiation of the oxidation of the Al surface. It then starts to increase with a certain rate during the phase of initiation of pore formation and it almost stabilizes when pore formation is on-going. This phase continues until the pores reach the interface with Si and it then drops suddenly to a minimum value. This current decrease corresponds to the initiation of oxidation of the Si surface underneath the PAA film [21]. The anodization curve of the sample PAA/S-5 min followed the same behavior with that described above, which means that a thin SiO2 film was formed underneath the PtSi layer by oxygen diffusion through the silicide. On the other hand, in the other two cases of samples PAA/S-15 and PAA/S-30 an abrupt increase of the current density with time was observed at the end of Al oxidation. As it will be illustrated below in the TEM images, this is due to the fact that the pore bottom reaches the surface of metal dots present on the PtSi film in these two last samples and an important leakage current flows to the Si substrate through these dots.


Porous anodic alumina on galvanically grown PtSi layer for application in template-assisted Si nanowire growth.

Michelakaki I, Nassiopoulou AG, Stavrinidou E, Breza K, Frangis N - Nanoscale Res Lett (2011)

Current-time anodization curves of an Al film on Si and on different PtSi/Si substrates (samples S-5 min, S-15 min, and S-30 min). In all cases, the Al film thickness was 500 nm. The anodization curve of sample Al/S-5 min is quite similar to that of Al/Si, while in the cases of samples Al/S-15 min and Al/S-30 min the current increases significantly when the PAA film reaches the underlying surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211510&req=5

Figure 5: Current-time anodization curves of an Al film on Si and on different PtSi/Si substrates (samples S-5 min, S-15 min, and S-30 min). In all cases, the Al film thickness was 500 nm. The anodization curve of sample Al/S-5 min is quite similar to that of Al/Si, while in the cases of samples Al/S-15 min and Al/S-30 min the current increases significantly when the PAA film reaches the underlying surface.
Mentions: Porous anodic alumina (PAA) can be grown on Si by anodic oxidation of an Al film. In this work, we investigated the formation of a PAA template on top of the PtSi layer with the objective to use the PtSi layer underneath as a catalyst for the formation of Si nanowires into the alumina pores. We used three of the PtSi films grown above, namely S-5 min, S-15 nm and S-30 min. An Al film, 500 nm thick, was deposited on the PtSi/Si substrate and an Al ohmic contact was formed on the backside of the wafer. The samples were then anodized in sulfuric acid aqueous solution at an anodization voltage of 20 V. The corresponding current-time anodization curves, compared to the one obtained without the PtSi layer, are shown in Figure 5. The general form of the curves is the same as that of the Al/Si anodization curve up to the time that the pores reach the Al2O3/Si or Al2O3/PtSi interface. The different phases of the anodization process are as follows [21]: At the very beginning of the anodization the current drops spontaneously to a lower value due to initiation of the oxidation of the Al surface. It then starts to increase with a certain rate during the phase of initiation of pore formation and it almost stabilizes when pore formation is on-going. This phase continues until the pores reach the interface with Si and it then drops suddenly to a minimum value. This current decrease corresponds to the initiation of oxidation of the Si surface underneath the PAA film [21]. The anodization curve of the sample PAA/S-5 min followed the same behavior with that described above, which means that a thin SiO2 film was formed underneath the PtSi layer by oxygen diffusion through the silicide. On the other hand, in the other two cases of samples PAA/S-15 and PAA/S-30 an abrupt increase of the current density with time was observed at the end of Al oxidation. As it will be illustrated below in the TEM images, this is due to the fact that the pore bottom reaches the surface of metal dots present on the PtSi film in these two last samples and an important leakage current flows to the Si substrate through these dots.

Bottom Line: We report on the fabrication and morphology/structural characterization of a porous anodic alumina (PAA)/PtSi nano-template for use as matrix in template-assisted Si nanowire growth on a Si substrate.The PtSi layer was formed by electroless deposition from an aqueous solution containing the metal salt and HF, while the PAA membrane by anodizing an Al film deposited on the PtSi layer.The morphology and structure of the PtSi layer and of the alumina membrane on top were studied by Scanning and High Resolution Transmission Electron Microscopies (SEM, HRTEM).

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microelectronics, NCSR Demokritos, Terma Patriarchou Grigoriou, Aghia Paraskevi, 153 10, Athens, Greece. A.Nassiopoulou@imel.demokritos.gr.

ABSTRACT
We report on the fabrication and morphology/structural characterization of a porous anodic alumina (PAA)/PtSi nano-template for use as matrix in template-assisted Si nanowire growth on a Si substrate. The PtSi layer was formed by electroless deposition from an aqueous solution containing the metal salt and HF, while the PAA membrane by anodizing an Al film deposited on the PtSi layer. The morphology and structure of the PtSi layer and of the alumina membrane on top were studied by Scanning and High Resolution Transmission Electron Microscopies (SEM, HRTEM). Cross sectional HRTEM images combined with electron diffraction (ED) were used to characterize the different interfaces between Si, PtSi and porous anodic alumina.

No MeSH data available.


Related in: MedlinePlus