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In situ Control of Si/Ge Growth on Stripe-Patterned Substrates Using Reflection High-Energy Electron Diffraction and Scanning Tunneling Microscopy.

Sanduijav B, Matei DG, Springholz G - Nanoscale Res Lett (2010)

Bottom Line: At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes.These observations are in excellent agreement with STM images recorded at different Ge coverages.The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
Si and Ge growth on the stripe-patterned Si (001) substrates is studied using in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). During Si buffer growth, the evolution of RHEED patterns reveals a rapid change of the stripe morphology from a multifaceted "U" to a single-faceted "V" geometry with {119} sidewall facets. This allows to control the pattern morphology and to stop Si buffer growth once a well-defined stripe geometry is formed. Subsequent Ge growth on "V"-shaped stripes was performed at two different temperatures of 520 and 600°C. At low temperature of 520°C, pronounced sidewall ripples are formed at a critical coverage of 4.1 monolayers as revealed by the appearance of splitted diffraction streaks in RHEED. At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes. These observations are in excellent agreement with STM images recorded at different Ge coverages. Therefore, RHEED is an efficient tool for in situ control of the growth process on stripe-patterned substrate templates. The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates.

No MeSH data available.


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Successive Ge growth on patterned Si substrates with “V”-shaped stripes for two different substrate temperatures of Ts = 520°C (top) and 600°C (bottom) as seen by STM (500 × 500 nm2 images). The Ge coverage increases from 4.5 ML on the left hand side where sidewall ripple formation starts, to 5.1 ML in the middle, to finally to 6 ML, respectively, 7 ML on the right hand side. The average ripple height at 4.5 ML coverage is 9.3 ± 0.5 Å at 520°C and 5.7 ± 0.5 Å at 600°C. Dome islands are only formed at the higher growth temperature and are aligned at the bottom of the grooves. The surface orientation maps of the STM images are shown as insets in which the observed {001}, {105}, {113}, and {15 3 23} facet spots are indicated by the symbols
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Figure 5: Successive Ge growth on patterned Si substrates with “V”-shaped stripes for two different substrate temperatures of Ts = 520°C (top) and 600°C (bottom) as seen by STM (500 × 500 nm2 images). The Ge coverage increases from 4.5 ML on the left hand side where sidewall ripple formation starts, to 5.1 ML in the middle, to finally to 6 ML, respectively, 7 ML on the right hand side. The average ripple height at 4.5 ML coverage is 9.3 ± 0.5 Å at 520°C and 5.7 ± 0.5 Å at 600°C. Dome islands are only formed at the higher growth temperature and are aligned at the bottom of the grooves. The surface orientation maps of the STM images are shown as insets in which the observed {001}, {105}, {113}, and {15 3 23} facet spots are indicated by the symbols

Mentions: The surface structure formed in this roughening transition is revealed by the STM images displayed in row of Fig. 5 recorded after 4.5, 5.1, and 7 ML Ge growth. Already at 4.5 ML coverage (Fig. 5a), the STM image shows that the {11 10} sidewalls of the stripes are fully covered by ripples oriented perpendicularly to the [110] stripe direction. The ripples consist of alternating {105} microfacets, which is proven by the corresponding surface orientation map shown as insert. The average ripple height amounts to 9.3 Å, which is about twice of the deposited Ge thickness. Comparing RHEED and STM data, the extra RHEED diffraction spots appearing at this coverage can be directly assigned to this ripple formation, and the splitting of these diffraction spots is explained by the fact that the ripples on opposite sidewalls are tilted by 16° (=2 × 8°) with respect to each other. At 5.1 ML Ge coverage (Fig. 5b), additional pyramids and hut islands with {105} sidewall facets start to nucleate on the ridges of the stripes, and their density subsequently increases such that at 7 ML coverage (Fig. 5c), the ridges are decorated by these islands. At the same time, a coarsening and thickening of ripples on the sidewalls occurs. This is in contrast to the expected Ge accumulation at the bottom of the grooves, indicating that there is only little lateral redistribution of the deposited Ge adatoms. Thus, at 520°C, lateral Ge mass transport is inhibited due to slow surface diffusion. Moreover, the nucleation of Ge islands at the edges of the ridges indicates that there is an additional hopping barrier at the edges between the ridges and the sidewall facets.


In situ Control of Si/Ge Growth on Stripe-Patterned Substrates Using Reflection High-Energy Electron Diffraction and Scanning Tunneling Microscopy.

Sanduijav B, Matei DG, Springholz G - Nanoscale Res Lett (2010)

Successive Ge growth on patterned Si substrates with “V”-shaped stripes for two different substrate temperatures of Ts = 520°C (top) and 600°C (bottom) as seen by STM (500 × 500 nm2 images). The Ge coverage increases from 4.5 ML on the left hand side where sidewall ripple formation starts, to 5.1 ML in the middle, to finally to 6 ML, respectively, 7 ML on the right hand side. The average ripple height at 4.5 ML coverage is 9.3 ± 0.5 Å at 520°C and 5.7 ± 0.5 Å at 600°C. Dome islands are only formed at the higher growth temperature and are aligned at the bottom of the grooves. The surface orientation maps of the STM images are shown as insets in which the observed {001}, {105}, {113}, and {15 3 23} facet spots are indicated by the symbols
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2991170&req=5

Figure 5: Successive Ge growth on patterned Si substrates with “V”-shaped stripes for two different substrate temperatures of Ts = 520°C (top) and 600°C (bottom) as seen by STM (500 × 500 nm2 images). The Ge coverage increases from 4.5 ML on the left hand side where sidewall ripple formation starts, to 5.1 ML in the middle, to finally to 6 ML, respectively, 7 ML on the right hand side. The average ripple height at 4.5 ML coverage is 9.3 ± 0.5 Å at 520°C and 5.7 ± 0.5 Å at 600°C. Dome islands are only formed at the higher growth temperature and are aligned at the bottom of the grooves. The surface orientation maps of the STM images are shown as insets in which the observed {001}, {105}, {113}, and {15 3 23} facet spots are indicated by the symbols
Mentions: The surface structure formed in this roughening transition is revealed by the STM images displayed in row of Fig. 5 recorded after 4.5, 5.1, and 7 ML Ge growth. Already at 4.5 ML coverage (Fig. 5a), the STM image shows that the {11 10} sidewalls of the stripes are fully covered by ripples oriented perpendicularly to the [110] stripe direction. The ripples consist of alternating {105} microfacets, which is proven by the corresponding surface orientation map shown as insert. The average ripple height amounts to 9.3 Å, which is about twice of the deposited Ge thickness. Comparing RHEED and STM data, the extra RHEED diffraction spots appearing at this coverage can be directly assigned to this ripple formation, and the splitting of these diffraction spots is explained by the fact that the ripples on opposite sidewalls are tilted by 16° (=2 × 8°) with respect to each other. At 5.1 ML Ge coverage (Fig. 5b), additional pyramids and hut islands with {105} sidewall facets start to nucleate on the ridges of the stripes, and their density subsequently increases such that at 7 ML coverage (Fig. 5c), the ridges are decorated by these islands. At the same time, a coarsening and thickening of ripples on the sidewalls occurs. This is in contrast to the expected Ge accumulation at the bottom of the grooves, indicating that there is only little lateral redistribution of the deposited Ge adatoms. Thus, at 520°C, lateral Ge mass transport is inhibited due to slow surface diffusion. Moreover, the nucleation of Ge islands at the edges of the ridges indicates that there is an additional hopping barrier at the edges between the ridges and the sidewall facets.

Bottom Line: At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes.These observations are in excellent agreement with STM images recorded at different Ge coverages.The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
Si and Ge growth on the stripe-patterned Si (001) substrates is studied using in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). During Si buffer growth, the evolution of RHEED patterns reveals a rapid change of the stripe morphology from a multifaceted "U" to a single-faceted "V" geometry with {119} sidewall facets. This allows to control the pattern morphology and to stop Si buffer growth once a well-defined stripe geometry is formed. Subsequent Ge growth on "V"-shaped stripes was performed at two different temperatures of 520 and 600°C. At low temperature of 520°C, pronounced sidewall ripples are formed at a critical coverage of 4.1 monolayers as revealed by the appearance of splitted diffraction streaks in RHEED. At 600°C, the ripple onset is shifted toward higher coverages, and at 5.2 monolayers dome islands are formed at the bottom of the stripes. These observations are in excellent agreement with STM images recorded at different Ge coverages. Therefore, RHEED is an efficient tool for in situ control of the growth process on stripe-patterned substrate templates. The comparison of the results obtained at different temperature reveals the importance of kinetics on the island formation process on patterned substrates.

No MeSH data available.


Related in: MedlinePlus