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Formation of silicon nanodots via ion beam sputtering of ultrathin gold thin film coatings on Si.

El-Atwani O, Ortoleva S, Cimaroli A, Allain JP - Nanoscale Res Lett (2011)

Bottom Line: Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2.In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization.In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA. oelatwan@purdue.edu.

ABSTRACT
Ion beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2. In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding.

No MeSH data available.


Relative concentration of gold. Relative concentration of gold in the sample during irradiation as a function of fluence after LEISS and XPS quantification. The plot of relative concentration (%Au) versus fluence displays two regions (A and B). Gold sputtering takes place in region A, whereas gold-silicon mixing and preferential sputtering of gold occurs in region B. The upper right inset is a magnification of the split between regions A and B.
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Figure 4: Relative concentration of gold. Relative concentration of gold in the sample during irradiation as a function of fluence after LEISS and XPS quantification. The plot of relative concentration (%Au) versus fluence displays two regions (A and B). Gold sputtering takes place in region A, whereas gold-silicon mixing and preferential sputtering of gold occurs in region B. The upper right inset is a magnification of the split between regions A and B.

Mentions: To elucidate about the role of gold during the nanopatterning process, a quantification of LEISS and XPS spectra was performed. The quantification results are shown in Figure 4. Both the ISS and the XPS quantification output curves indicate two different reduction mechanisms of gold concentration. Initially, gold is sputtered until the 200-eV argon ions are able to penetrate the thin gold film (penetration depth of argon is around 2 nm10) and induce mixing with silicon. This is marked by a large negative slope in the gold relative concentration versus fluence data shown in Figure 4, region A. The gold concentration, however, was not uniform during this period. This is due to inhomogeneities (islands) of the gold film confirmed by SEM, which during sputtering, result in more silicon areas being uncovered due to the dissimilar sputter yield of Au atoms compared to Si. Furthermore, Si and Au form a eutectic at a concentration of about 31 a/o Si-Au and temperature of 370°C. Therefore, ion-induced mixing could effectively induce an enhanced surface diffusion that redistributes Au from peak to valleys of the islands that further lead to erosion of Au. Note that when surface structures are formed, in principle, the valleys erode faster than the peaks due to the proximity of the incident particle energy deposition density to surface atoms according to the Bradley-Harper and Sigmund models [16,17].


Formation of silicon nanodots via ion beam sputtering of ultrathin gold thin film coatings on Si.

El-Atwani O, Ortoleva S, Cimaroli A, Allain JP - Nanoscale Res Lett (2011)

Relative concentration of gold. Relative concentration of gold in the sample during irradiation as a function of fluence after LEISS and XPS quantification. The plot of relative concentration (%Au) versus fluence displays two regions (A and B). Gold sputtering takes place in region A, whereas gold-silicon mixing and preferential sputtering of gold occurs in region B. The upper right inset is a magnification of the split between regions A and B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211498&req=5

Figure 4: Relative concentration of gold. Relative concentration of gold in the sample during irradiation as a function of fluence after LEISS and XPS quantification. The plot of relative concentration (%Au) versus fluence displays two regions (A and B). Gold sputtering takes place in region A, whereas gold-silicon mixing and preferential sputtering of gold occurs in region B. The upper right inset is a magnification of the split between regions A and B.
Mentions: To elucidate about the role of gold during the nanopatterning process, a quantification of LEISS and XPS spectra was performed. The quantification results are shown in Figure 4. Both the ISS and the XPS quantification output curves indicate two different reduction mechanisms of gold concentration. Initially, gold is sputtered until the 200-eV argon ions are able to penetrate the thin gold film (penetration depth of argon is around 2 nm10) and induce mixing with silicon. This is marked by a large negative slope in the gold relative concentration versus fluence data shown in Figure 4, region A. The gold concentration, however, was not uniform during this period. This is due to inhomogeneities (islands) of the gold film confirmed by SEM, which during sputtering, result in more silicon areas being uncovered due to the dissimilar sputter yield of Au atoms compared to Si. Furthermore, Si and Au form a eutectic at a concentration of about 31 a/o Si-Au and temperature of 370°C. Therefore, ion-induced mixing could effectively induce an enhanced surface diffusion that redistributes Au from peak to valleys of the islands that further lead to erosion of Au. Note that when surface structures are formed, in principle, the valleys erode faster than the peaks due to the proximity of the incident particle energy deposition density to surface atoms according to the Bradley-Harper and Sigmund models [16,17].

Bottom Line: Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2.In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization.In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA. oelatwan@purdue.edu.

ABSTRACT
Ion beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2. In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding.

No MeSH data available.