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Self-organized chains of nanodots induced by an off-normal incident beam.

Lee S, Wang L, Lu W - Nanoscale Res Lett (2011)

Bottom Line: We propose a model to show that under off-normal bombardment of an incident ion beam, a solid surface may spontaneously form nanoscale dots lining up into chains perpendicular to the incident beam direction.We attribute the self-organization behavior to surface instability under concurrent surface kinetics and to a shadow effect that causes the self-alignment of dots.The fundamental mechanism may be applicable to diverse systems, suggesting an effective approach for nanofabrication.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA. weilu@umich.edu.

ABSTRACT
We propose a model to show that under off-normal bombardment of an incident ion beam, a solid surface may spontaneously form nanoscale dots lining up into chains perpendicular to the incident beam direction. These dots demonstrate a highly ordered hexagonal pattern. We attribute the self-organization behavior to surface instability under concurrent surface kinetics and to a shadow effect that causes the self-alignment of dots. The fundamental mechanism may be applicable to diverse systems, suggesting an effective approach for nanofabrication.

No MeSH data available.


Simulation results at t = 10,000 for different values of η. The results reveal how the strength of the shadow effect affects the pattern. (a) No shadow effect (η = 0) and (b) weak shadow effect (η = 0.5).
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Figure 3: Simulation results at t = 10,000 for different values of η. The results reveal how the strength of the shadow effect affects the pattern. (a) No shadow effect (η = 0) and (b) weak shadow effect (η = 0.5).

Mentions: Representative simulation results are shown in Figures 2 and 3. The following normalized parameters were chosen: ρ = 0.24, β = 1, α = 1, and λ = 1 [27]. Figure 2 shows an evolution sequence for η = 1.0 from t = 0 to t = 10,000. Figure 2a shows the initial substrate surface at t = 0. After a short time of bombardment, small peaks quickly emerge and form a wavy chain pattern, as shown in Figure 2b. Linear terms are dominant during the early stage of evolution. The nonlinear term representing the shadow effect does not reflect itself significantly in the result. Dots start to emerge and grow quickly after t = 1,000, as shown in Figure 2c for t = 1,400. As of now, the dots are randomly distributed without showing any particular order. The height growth of dots slows down after t = 2,000, since the nonlinear term starts to affect the growth. Figures 2d and 2e show that the dots start to line up and form short chains. Overall, these short chains appear to orientate along the y axis, though the orientation of a single chain is less definite. During this stage, the dominating behavior is the change of the location of dots particularly at dislocation regions, while their heights remain almost constant. Over time, the chains become more ordered. Figure 2f shows that at t = 10,000, the chains are clearly aligned along the y axis, which is perpendicular to the incident beam direction. The dots form a hexagonal pattern and their sizes are uniform. These simulation results are consistent with experimental observations [9].


Self-organized chains of nanodots induced by an off-normal incident beam.

Lee S, Wang L, Lu W - Nanoscale Res Lett (2011)

Simulation results at t = 10,000 for different values of η. The results reveal how the strength of the shadow effect affects the pattern. (a) No shadow effect (η = 0) and (b) weak shadow effect (η = 0.5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211850&req=5

Figure 3: Simulation results at t = 10,000 for different values of η. The results reveal how the strength of the shadow effect affects the pattern. (a) No shadow effect (η = 0) and (b) weak shadow effect (η = 0.5).
Mentions: Representative simulation results are shown in Figures 2 and 3. The following normalized parameters were chosen: ρ = 0.24, β = 1, α = 1, and λ = 1 [27]. Figure 2 shows an evolution sequence for η = 1.0 from t = 0 to t = 10,000. Figure 2a shows the initial substrate surface at t = 0. After a short time of bombardment, small peaks quickly emerge and form a wavy chain pattern, as shown in Figure 2b. Linear terms are dominant during the early stage of evolution. The nonlinear term representing the shadow effect does not reflect itself significantly in the result. Dots start to emerge and grow quickly after t = 1,000, as shown in Figure 2c for t = 1,400. As of now, the dots are randomly distributed without showing any particular order. The height growth of dots slows down after t = 2,000, since the nonlinear term starts to affect the growth. Figures 2d and 2e show that the dots start to line up and form short chains. Overall, these short chains appear to orientate along the y axis, though the orientation of a single chain is less definite. During this stage, the dominating behavior is the change of the location of dots particularly at dislocation regions, while their heights remain almost constant. Over time, the chains become more ordered. Figure 2f shows that at t = 10,000, the chains are clearly aligned along the y axis, which is perpendicular to the incident beam direction. The dots form a hexagonal pattern and their sizes are uniform. These simulation results are consistent with experimental observations [9].

Bottom Line: We propose a model to show that under off-normal bombardment of an incident ion beam, a solid surface may spontaneously form nanoscale dots lining up into chains perpendicular to the incident beam direction.We attribute the self-organization behavior to surface instability under concurrent surface kinetics and to a shadow effect that causes the self-alignment of dots.The fundamental mechanism may be applicable to diverse systems, suggesting an effective approach for nanofabrication.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA. weilu@umich.edu.

ABSTRACT
We propose a model to show that under off-normal bombardment of an incident ion beam, a solid surface may spontaneously form nanoscale dots lining up into chains perpendicular to the incident beam direction. These dots demonstrate a highly ordered hexagonal pattern. We attribute the self-organization behavior to surface instability under concurrent surface kinetics and to a shadow effect that causes the self-alignment of dots. The fundamental mechanism may be applicable to diverse systems, suggesting an effective approach for nanofabrication.

No MeSH data available.