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Hierarchical ZnO nanostructures with blooming flowers driven by screw dislocations.

Huang C, Shi R, Amini A, Wu Z, Xu S, Zhang L, Cao W, Feng J, Song H, Shi Y, Wang N, Cheng C - Sci Rep (2015)

Bottom Line: Hierarchical ZnO nanostructures with a large yield were fabricated by a simple thermal evaporation method.The spines for as-synthesized hierarchical structures can be nanowires, nanobelts, nanodendrites, nanobrushes, etc.This growth phenomenon determines the key role of polar sites in the fabrication of hierarchical structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology, Shenzhen, 518055, China.

ABSTRACT
Hierarchical ZnO nanostructures with a large yield were fabricated by a simple thermal evaporation method. For the first time, novel ZnO flowers were observed blooming at certain sites of a variety of spines, identified as Zn-terminated polar (0001) planes or tips. The spines for as-synthesized hierarchical structures can be nanowires, nanobelts, nanodendrites, nanobrushes, etc. This growth phenomenon determines the key role of polar sites in the fabrication of hierarchical structures. The spiral feature of ZnO flowers indicates an unusual screw dislocation driven growth mechanism, which is attributed to a high concentration of Zn vapor.

No MeSH data available.


Related in: MedlinePlus

SEM images of (a) Belt-like hierarchical structures along , (b) along with flowers opening toward the [0001] direction. (c) Some particles are observed on the ridge of the  side of the belt-like hierarchical structure. (d) – (e) Developing morphologies of belt-like hierarchical structures. (f) TEM image and SAED showing that the belt is a single crystal with the spine along and its projection plane perpendicular to [0001]. (g) – (j) are SEM images of flowers grown on thick rectangular belts along the ,  and  directions. The scale bars are 10 μm for (a), (b), (d) and (h) – (j), 5 μm for (e), 2 μm for (c) and (f), and 200 nm for (i).
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f3: SEM images of (a) Belt-like hierarchical structures along , (b) along with flowers opening toward the [0001] direction. (c) Some particles are observed on the ridge of the side of the belt-like hierarchical structure. (d) – (e) Developing morphologies of belt-like hierarchical structures. (f) TEM image and SAED showing that the belt is a single crystal with the spine along and its projection plane perpendicular to [0001]. (g) – (j) are SEM images of flowers grown on thick rectangular belts along the , and directions. The scale bars are 10 μm for (a), (b), (d) and (h) – (j), 5 μm for (e), 2 μm for (c) and (f), and 200 nm for (i).

Mentions: As shown in Fig. 1b, there are two kinds of type I - belt-like hierarchical structures coexisting in the low deposition temperature region: Type IA has spines of V-shape belts (see the left panel in Fig. 1b, Figs. 3a–g) and type IB has spines of rectangular belts (see the right panel in Fig. 1b, Figs. 4h–j). The flowers of type IA and IB are assembled in-line only on one side of these belts. Fig. 3c and Figs. 3h–j depict the other sides of these belts which are smooth apart from nanoparticles growth along their axes. This phenomenon is produced by different growth rates on the active (0001)-Zn and inert terminated surfaces12. ZnO hexagonal flowers have two oriented stands on the spines in type IA, that is, either parallel or perpendicular to the axis of the spines (Figs. 3a and b). This indicates the existence of ZnO spines with two usual growth directions: and .Our observation shows that the former stand orientation exists much more than the latter. In addition, Figs. 3d–f show the intermediate structures toward the formation of type IA hierarchical structures. It is clear that the extended growth of triangle thin films alongside the one-dimensional spine (Fig. 3d) and their integration lead to the formation of the long V-shape belt (Fig. 3e). It was found that small isolated islands appear on the axis (Fig. 3e) and flowers originate from these islands by helical growth (see Fig. 3f). These petals of flowers extend in the same direction of the wings. The TEM image of a type IA hierarchical structure with the hexagonal side parallel to the axis of spines is shown in Fig. 3i and the corresponding SAED in the inset of this Figure identifies the growth direction of the spine is along . It was found that the color in the middle part of the V-shape belt is much darker comparing to that in its edge. This is attributed to faster growth in the middle part because the naked Zn-terminated sites are quite active, supporting a self-catalytic growth2. Figs. 3h–j show typical SEM images of type IB hierarchical structure with flowers grown on thick rectangular belts. Spines of belt with three main growth orientations are the main products and the flowers fabricated on these spines have either perpendicular or inclined open directions the same as the spine direction. Comparing these results with Fig. 2c, the growth directions of spines are determined as , and . And all the flowers and thin films that extend from the spines in type I have large opening angles consisting of planes (Figs. 2d and e).


Hierarchical ZnO nanostructures with blooming flowers driven by screw dislocations.

Huang C, Shi R, Amini A, Wu Z, Xu S, Zhang L, Cao W, Feng J, Song H, Shi Y, Wang N, Cheng C - Sci Rep (2015)

SEM images of (a) Belt-like hierarchical structures along , (b) along with flowers opening toward the [0001] direction. (c) Some particles are observed on the ridge of the  side of the belt-like hierarchical structure. (d) – (e) Developing morphologies of belt-like hierarchical structures. (f) TEM image and SAED showing that the belt is a single crystal with the spine along and its projection plane perpendicular to [0001]. (g) – (j) are SEM images of flowers grown on thick rectangular belts along the ,  and  directions. The scale bars are 10 μm for (a), (b), (d) and (h) – (j), 5 μm for (e), 2 μm for (c) and (f), and 200 nm for (i).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4316161&req=5

f3: SEM images of (a) Belt-like hierarchical structures along , (b) along with flowers opening toward the [0001] direction. (c) Some particles are observed on the ridge of the side of the belt-like hierarchical structure. (d) – (e) Developing morphologies of belt-like hierarchical structures. (f) TEM image and SAED showing that the belt is a single crystal with the spine along and its projection plane perpendicular to [0001]. (g) – (j) are SEM images of flowers grown on thick rectangular belts along the , and directions. The scale bars are 10 μm for (a), (b), (d) and (h) – (j), 5 μm for (e), 2 μm for (c) and (f), and 200 nm for (i).
Mentions: As shown in Fig. 1b, there are two kinds of type I - belt-like hierarchical structures coexisting in the low deposition temperature region: Type IA has spines of V-shape belts (see the left panel in Fig. 1b, Figs. 3a–g) and type IB has spines of rectangular belts (see the right panel in Fig. 1b, Figs. 4h–j). The flowers of type IA and IB are assembled in-line only on one side of these belts. Fig. 3c and Figs. 3h–j depict the other sides of these belts which are smooth apart from nanoparticles growth along their axes. This phenomenon is produced by different growth rates on the active (0001)-Zn and inert terminated surfaces12. ZnO hexagonal flowers have two oriented stands on the spines in type IA, that is, either parallel or perpendicular to the axis of the spines (Figs. 3a and b). This indicates the existence of ZnO spines with two usual growth directions: and .Our observation shows that the former stand orientation exists much more than the latter. In addition, Figs. 3d–f show the intermediate structures toward the formation of type IA hierarchical structures. It is clear that the extended growth of triangle thin films alongside the one-dimensional spine (Fig. 3d) and their integration lead to the formation of the long V-shape belt (Fig. 3e). It was found that small isolated islands appear on the axis (Fig. 3e) and flowers originate from these islands by helical growth (see Fig. 3f). These petals of flowers extend in the same direction of the wings. The TEM image of a type IA hierarchical structure with the hexagonal side parallel to the axis of spines is shown in Fig. 3i and the corresponding SAED in the inset of this Figure identifies the growth direction of the spine is along . It was found that the color in the middle part of the V-shape belt is much darker comparing to that in its edge. This is attributed to faster growth in the middle part because the naked Zn-terminated sites are quite active, supporting a self-catalytic growth2. Figs. 3h–j show typical SEM images of type IB hierarchical structure with flowers grown on thick rectangular belts. Spines of belt with three main growth orientations are the main products and the flowers fabricated on these spines have either perpendicular or inclined open directions the same as the spine direction. Comparing these results with Fig. 2c, the growth directions of spines are determined as , and . And all the flowers and thin films that extend from the spines in type I have large opening angles consisting of planes (Figs. 2d and e).

Bottom Line: Hierarchical ZnO nanostructures with a large yield were fabricated by a simple thermal evaporation method.The spines for as-synthesized hierarchical structures can be nanowires, nanobelts, nanodendrites, nanobrushes, etc.This growth phenomenon determines the key role of polar sites in the fabrication of hierarchical structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology, Shenzhen, 518055, China.

ABSTRACT
Hierarchical ZnO nanostructures with a large yield were fabricated by a simple thermal evaporation method. For the first time, novel ZnO flowers were observed blooming at certain sites of a variety of spines, identified as Zn-terminated polar (0001) planes or tips. The spines for as-synthesized hierarchical structures can be nanowires, nanobelts, nanodendrites, nanobrushes, etc. This growth phenomenon determines the key role of polar sites in the fabrication of hierarchical structures. The spiral feature of ZnO flowers indicates an unusual screw dislocation driven growth mechanism, which is attributed to a high concentration of Zn vapor.

No MeSH data available.


Related in: MedlinePlus