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Crystallographic orientation-dependent pattern replication in direct imprint of aluminum nanostructures.

Yuan Y, Zhang J, Sun T, Liu C, Geng Y, Yan Y, Jin P - Nanoscale Res Lett (2015)

Bottom Line: We investigate the influence of crystallographic orientation on the microscopic deformation behavior of the substrate materials and its correlation with the macroscopic pattern replications.Furthermore, the surface mechanical properties of the patterned structures are qualitatively characterized by nanoindentation tests.It is found that the (010) orientation leads to a better quality of pattern replication of single-crystalline aluminum than the (111) orientation.

View Article: PubMed Central - PubMed

Affiliation: Center for Precision Engineering, Harbin Institute of Technology, Harbin, 150001 People's Republic of China.

ABSTRACT
In the present work, we perform molecular dynamics simulations corroborated by experimental validations to elucidate the underlying deformation mechanisms of single-crystalline aluminum under direct imprint using a rigid silicon master. We investigate the influence of crystallographic orientation on the microscopic deformation behavior of the substrate materials and its correlation with the macroscopic pattern replications. Furthermore, the surface mechanical properties of the patterned structures are qualitatively characterized by nanoindentation tests. Our results reveal that dislocation slip and deformation twinning are two primary plastic deformation modes of single-crystalline aluminum under the direct imprint. However, both the competition between the individual deformation mechanisms and the geometry between activated dislocation slip systems and imprinted surface vary with surface orientation, which in turn leads to a strong crystallographic orientation dependence of the pattern replications. It is found that the (010) orientation leads to a better quality of pattern replication of single-crystalline aluminum than the (111) orientation.

No MeSH data available.


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Defect evolutions during the direct imprint of Al(010). Instantaneous defect structures at a moving distance of (a) 1.32 nm, (b) 2.08 nm, and (c) 4.0 nm. (d) Instantaneous defect structures after completion of the withdrawing stage. Atoms are colored according to their CNA values.
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Fig5: Defect evolutions during the direct imprint of Al(010). Instantaneous defect structures at a moving distance of (a) 1.32 nm, (b) 2.08 nm, and (c) 4.0 nm. (d) Instantaneous defect structures after completion of the withdrawing stage. Atoms are colored according to their CNA values.

Mentions: To interpret the characteristics observed in the force-moving distance curves, Figure 5 presents defect evolutions during the direct imprint of the Al(010) substrate. Figure 5a shows that at a moving distance of 1.32 nm, there is no defect generated in the substrate, indicating that the material is undergoing pure elastic deformation. When the applied stress by the master reaches the critical resolve stress of the material, plastic deformation initiates through the nucleation of lattice partial dislocations from the penetrated surface. Dislocation nucleation releases accumulated elastic strain energy, which leads to the decrease of the force shown in Figure 3 [19]. Figure 5b shows that at a moving distance of 2.08 nm, there are defect zones composed of dislocation structures formed beneath each tooth of the master. However, the extent of defect zone beneath each tooth is not uniform with each other. While there are considerable partial dislocations bounced by intrinsic stacking fault formed in the vicinity of the second and fourth teeth, the defect zone is very small for the first and third teeth because of the activation of multiple slip systems. Upon further imprint, nucleated dislocations glide on neighboring {111} slip planes to approach each other, and their multiplication and interaction lead to the formation of sessile and glissile dislocation structures. Furthermore, the average distance between dislocations decreases with increasing dislocation density. Consequently, both dislocations and sessile dislocation structures block the motion of dislocations, which causes significant strain hardening which occurred in the imprinted material [25]. It is known that the deformation ability of ductile metallic materials dominantly depends on the ability of dislocation motion, and the strengthening of the material results in the deterioration of the ductility and the increase of the force, as shown in Figure 3. To accommodate further plastic deformation induced by the movement of the master, successive dislocations emit from the surface and subsequently glide on other two {111} slip planes. And there are mechanical twin boundaries (TBs) formed by the dissociation of partial dislocations, suggesting that deformation twinning is also one important deformation mode of single-crystalline aluminum under the direct imprint [26,27]. Figure 5c shows that the dislocation density within the substrate is high. We note that the fixed bottom may block the propagation of dislocations. Consequently, the force in the imprint stage increases with fluctuations, which are caused by successive nucleation or emission events of dislocations.Figure 5


Crystallographic orientation-dependent pattern replication in direct imprint of aluminum nanostructures.

Yuan Y, Zhang J, Sun T, Liu C, Geng Y, Yan Y, Jin P - Nanoscale Res Lett (2015)

Defect evolutions during the direct imprint of Al(010). Instantaneous defect structures at a moving distance of (a) 1.32 nm, (b) 2.08 nm, and (c) 4.0 nm. (d) Instantaneous defect structures after completion of the withdrawing stage. Atoms are colored according to their CNA values.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385152&req=5

Fig5: Defect evolutions during the direct imprint of Al(010). Instantaneous defect structures at a moving distance of (a) 1.32 nm, (b) 2.08 nm, and (c) 4.0 nm. (d) Instantaneous defect structures after completion of the withdrawing stage. Atoms are colored according to their CNA values.
Mentions: To interpret the characteristics observed in the force-moving distance curves, Figure 5 presents defect evolutions during the direct imprint of the Al(010) substrate. Figure 5a shows that at a moving distance of 1.32 nm, there is no defect generated in the substrate, indicating that the material is undergoing pure elastic deformation. When the applied stress by the master reaches the critical resolve stress of the material, plastic deformation initiates through the nucleation of lattice partial dislocations from the penetrated surface. Dislocation nucleation releases accumulated elastic strain energy, which leads to the decrease of the force shown in Figure 3 [19]. Figure 5b shows that at a moving distance of 2.08 nm, there are defect zones composed of dislocation structures formed beneath each tooth of the master. However, the extent of defect zone beneath each tooth is not uniform with each other. While there are considerable partial dislocations bounced by intrinsic stacking fault formed in the vicinity of the second and fourth teeth, the defect zone is very small for the first and third teeth because of the activation of multiple slip systems. Upon further imprint, nucleated dislocations glide on neighboring {111} slip planes to approach each other, and their multiplication and interaction lead to the formation of sessile and glissile dislocation structures. Furthermore, the average distance between dislocations decreases with increasing dislocation density. Consequently, both dislocations and sessile dislocation structures block the motion of dislocations, which causes significant strain hardening which occurred in the imprinted material [25]. It is known that the deformation ability of ductile metallic materials dominantly depends on the ability of dislocation motion, and the strengthening of the material results in the deterioration of the ductility and the increase of the force, as shown in Figure 3. To accommodate further plastic deformation induced by the movement of the master, successive dislocations emit from the surface and subsequently glide on other two {111} slip planes. And there are mechanical twin boundaries (TBs) formed by the dissociation of partial dislocations, suggesting that deformation twinning is also one important deformation mode of single-crystalline aluminum under the direct imprint [26,27]. Figure 5c shows that the dislocation density within the substrate is high. We note that the fixed bottom may block the propagation of dislocations. Consequently, the force in the imprint stage increases with fluctuations, which are caused by successive nucleation or emission events of dislocations.Figure 5

Bottom Line: We investigate the influence of crystallographic orientation on the microscopic deformation behavior of the substrate materials and its correlation with the macroscopic pattern replications.Furthermore, the surface mechanical properties of the patterned structures are qualitatively characterized by nanoindentation tests.It is found that the (010) orientation leads to a better quality of pattern replication of single-crystalline aluminum than the (111) orientation.

View Article: PubMed Central - PubMed

Affiliation: Center for Precision Engineering, Harbin Institute of Technology, Harbin, 150001 People's Republic of China.

ABSTRACT
In the present work, we perform molecular dynamics simulations corroborated by experimental validations to elucidate the underlying deformation mechanisms of single-crystalline aluminum under direct imprint using a rigid silicon master. We investigate the influence of crystallographic orientation on the microscopic deformation behavior of the substrate materials and its correlation with the macroscopic pattern replications. Furthermore, the surface mechanical properties of the patterned structures are qualitatively characterized by nanoindentation tests. Our results reveal that dislocation slip and deformation twinning are two primary plastic deformation modes of single-crystalline aluminum under the direct imprint. However, both the competition between the individual deformation mechanisms and the geometry between activated dislocation slip systems and imprinted surface vary with surface orientation, which in turn leads to a strong crystallographic orientation dependence of the pattern replications. It is found that the (010) orientation leads to a better quality of pattern replication of single-crystalline aluminum than the (111) orientation.

No MeSH data available.


Related in: MedlinePlus