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Evolution of morphology and microstructure of GaAs/GaSb nanowire heterostructures.

Shi S, Zhang Z, Lu Z, Shu H, Chen P, Li N, Zou J, Lu W - Nanoscale Res Lett (2015)

Bottom Line: The as-grown GaSb shell layer forms a wurtzite structure instead of the zinc blende structure that has been commonly reported.Meanwhile, a bulgy GaSb nanoplate also appears on top of GaAs/GaSb core-shell NWs and possesses a pure zinc blende phase.The growth mode for core-shell morphology and underlying mechanism for crystal phase selection of GaAs/GaSb nanowire heterostructures are discussed in detail.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai, 200083 China.

ABSTRACT
In this paper, we successfully grow GaAs/GaSb core-shell heterostructure nanowires (NWs) by molecular beam epitaxy (MBE). The as-grown GaSb shell layer forms a wurtzite structure instead of the zinc blende structure that has been commonly reported. Meanwhile, a bulgy GaSb nanoplate also appears on top of GaAs/GaSb core-shell NWs and possesses a pure zinc blende phase. The growth mode for core-shell morphology and underlying mechanism for crystal phase selection of GaAs/GaSb nanowire heterostructures are discussed in detail.

No MeSH data available.


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Structural and compositional details of the S3 segment and its neighboring NW from Figure2c. (a) A bright-field TEM image. (b) EDS linescan indicated by the red line in (a). (c) A representative EDS composition from the S3 segment. (d-e) HRTEM images corresponding to the two locations A-1 and A-2 shown in (a).
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Fig5: Structural and compositional details of the S3 segment and its neighboring NW from Figure2c. (a) A bright-field TEM image. (b) EDS linescan indicated by the red line in (a). (c) A representative EDS composition from the S3 segment. (d-e) HRTEM images corresponding to the two locations A-1 and A-2 shown in (a).

Mentions: Figure 5 shows the structural and compositional details of the top bulgy nanoplate and its neighboring segment, with their boundary indicated by a red dashed line in Figure 5a. Figure 5b shows the EDS linescan taken from the red line marked in Figure 5a, from which we find that arsenic signal only covers a radial length of about 10 nm, and its intensity is very small. Compared with Figure 4b in which strong As signal lasts a distance of about 30 nm radially, it can be inferred that GaAs NW should have a tapering shape, and this tapering morphology can also be verified by the TEM image of Figure 2a, b. Similar morphological variation has been well reported [31]. In fact, along the growth direction of the core-shell segment between the red solid line and red dashed line in Figure 5a, arsenic composition decreases quickly, becoming finally undetectable at the boundary position (indicated by the red dashed line). As for the top S3-type nanoplate, Figure 5c presents a typical EDS measurement, which clearly demonstrates its composition of pure GaSb. Figure 5d provides a high-resolution TEM image of the NW segment A-1 shown in Figure 5a, which spans both S2 and S3 segments. A transition from WZ-dominant structure to pure ZB phase is clearly depicted. The HRTEM image of the NW segment A-2 further demonstrates the pure ZB structure of the top GaSb nanoplate (see Figure 5e). Besides, except for the GaSb shell layer grown on GaAs core NW, the pure GaSb top nanoplate also exhibits a tendency of lateral growth, which can be verified more remarkably by the large diameter of the S3 segment in Figure 2b. Our extensive TEM investigations also confirm the formation of core-shell structures in other samples. However, in the previous work reported by de la Mata et al. [32], the axial GaAs/GaSb NW heterostructures have been grown by MBE. But the growth condition adopted by them is quite different from that used in our study. Maybe, the lower growth temperature and smaller V/III ratios used here is more beneficial to the growth of GaSb shell layers. This implies that through careful control of growth parameters, both axial and core-shell GaAs/GaSb NW heterostructures can be obtained in a MBE system.Figure 5


Evolution of morphology and microstructure of GaAs/GaSb nanowire heterostructures.

Shi S, Zhang Z, Lu Z, Shu H, Chen P, Li N, Zou J, Lu W - Nanoscale Res Lett (2015)

Structural and compositional details of the S3 segment and its neighboring NW from Figure2c. (a) A bright-field TEM image. (b) EDS linescan indicated by the red line in (a). (c) A representative EDS composition from the S3 segment. (d-e) HRTEM images corresponding to the two locations A-1 and A-2 shown in (a).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig5: Structural and compositional details of the S3 segment and its neighboring NW from Figure2c. (a) A bright-field TEM image. (b) EDS linescan indicated by the red line in (a). (c) A representative EDS composition from the S3 segment. (d-e) HRTEM images corresponding to the two locations A-1 and A-2 shown in (a).
Mentions: Figure 5 shows the structural and compositional details of the top bulgy nanoplate and its neighboring segment, with their boundary indicated by a red dashed line in Figure 5a. Figure 5b shows the EDS linescan taken from the red line marked in Figure 5a, from which we find that arsenic signal only covers a radial length of about 10 nm, and its intensity is very small. Compared with Figure 4b in which strong As signal lasts a distance of about 30 nm radially, it can be inferred that GaAs NW should have a tapering shape, and this tapering morphology can also be verified by the TEM image of Figure 2a, b. Similar morphological variation has been well reported [31]. In fact, along the growth direction of the core-shell segment between the red solid line and red dashed line in Figure 5a, arsenic composition decreases quickly, becoming finally undetectable at the boundary position (indicated by the red dashed line). As for the top S3-type nanoplate, Figure 5c presents a typical EDS measurement, which clearly demonstrates its composition of pure GaSb. Figure 5d provides a high-resolution TEM image of the NW segment A-1 shown in Figure 5a, which spans both S2 and S3 segments. A transition from WZ-dominant structure to pure ZB phase is clearly depicted. The HRTEM image of the NW segment A-2 further demonstrates the pure ZB structure of the top GaSb nanoplate (see Figure 5e). Besides, except for the GaSb shell layer grown on GaAs core NW, the pure GaSb top nanoplate also exhibits a tendency of lateral growth, which can be verified more remarkably by the large diameter of the S3 segment in Figure 2b. Our extensive TEM investigations also confirm the formation of core-shell structures in other samples. However, in the previous work reported by de la Mata et al. [32], the axial GaAs/GaSb NW heterostructures have been grown by MBE. But the growth condition adopted by them is quite different from that used in our study. Maybe, the lower growth temperature and smaller V/III ratios used here is more beneficial to the growth of GaSb shell layers. This implies that through careful control of growth parameters, both axial and core-shell GaAs/GaSb NW heterostructures can be obtained in a MBE system.Figure 5

Bottom Line: The as-grown GaSb shell layer forms a wurtzite structure instead of the zinc blende structure that has been commonly reported.Meanwhile, a bulgy GaSb nanoplate also appears on top of GaAs/GaSb core-shell NWs and possesses a pure zinc blende phase.The growth mode for core-shell morphology and underlying mechanism for crystal phase selection of GaAs/GaSb nanowire heterostructures are discussed in detail.

View Article: PubMed Central - PubMed

Affiliation: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai, 200083 China.

ABSTRACT
In this paper, we successfully grow GaAs/GaSb core-shell heterostructure nanowires (NWs) by molecular beam epitaxy (MBE). The as-grown GaSb shell layer forms a wurtzite structure instead of the zinc blende structure that has been commonly reported. Meanwhile, a bulgy GaSb nanoplate also appears on top of GaAs/GaSb core-shell NWs and possesses a pure zinc blende phase. The growth mode for core-shell morphology and underlying mechanism for crystal phase selection of GaAs/GaSb nanowire heterostructures are discussed in detail.

No MeSH data available.


Related in: MedlinePlus