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MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation.

E Y, Hao Z, Yu J, Wu C, Liu R, Wang L, Xiong B, Wang J, Han Y, Sun C, Luo Y - Nanoscale Res Lett (2015)

Bottom Line: The influence of growth conditions on the morphologies of AlN NWs is carefully investigated.Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms.Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

View Article: PubMed Central - PubMed

Affiliation: Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. eyx11@mails.tsinghua.edu.cn.

ABSTRACT
By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

No MeSH data available.


Related in: MedlinePlus

SEM image of the surface of the AlN NW sample etched by 10 % KOH solution for 60 s
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Fig8: SEM image of the surface of the AlN NW sample etched by 10 % KOH solution for 60 s

Mentions: The reason for the formation of island-like films instead of newly nucleated NWs may be related to the polarity of AlN crystal. Fernández-Garrido et al. [17] have made a statement that all spontaneously formed nitride NWs by MBE are N-polar, and NWs cannot grow on III-polar nitride epilayers. On the other hand, we have already reported that the AlN islands formed after the aluminization process are N-polar, while the AlN films directly grown on β-Si3N4 are Al-polar [10]. At the beginning of AlN NW growth, the bare Si (111) surface between AlN islands is unintentionally nitridated to form β-Si3N4. Then, based on this β-Si3N4, Al-polar AlN films are formed because the Al adatoms prefer to react with active N radicals rather than β-Si3N4. In order to examine the polarities of the AlN NWs and island-like films, the sample was treated in 10 % KOH solution for 60 s at 80 °C. KOH solution can only etch N-polar AlN, while Al-polar AlN is resistant to KOH [18]. The SEM image of the etched surface is shown in Fig. 8. It can be seen that there are no NWs remaining on the surface but many hexagonal holes which have nearly the same density and average diameter as the AlN NWs, and the island-like films around the holes are not etched, almost keeping the original morphologies. This is a clear evidence that the AlN NWs are N-polar whereas the films are Al-polar. Furthermore, the residuals in the holes resulted from the anisotropic etching rate with respect to different crystalline planes, and some small holes can be attributed to the N-polar inversion domains in the films.Fig. 8


MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation.

E Y, Hao Z, Yu J, Wu C, Liu R, Wang L, Xiong B, Wang J, Han Y, Sun C, Luo Y - Nanoscale Res Lett (2015)

SEM image of the surface of the AlN NW sample etched by 10 % KOH solution for 60 s
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593981&req=5

Fig8: SEM image of the surface of the AlN NW sample etched by 10 % KOH solution for 60 s
Mentions: The reason for the formation of island-like films instead of newly nucleated NWs may be related to the polarity of AlN crystal. Fernández-Garrido et al. [17] have made a statement that all spontaneously formed nitride NWs by MBE are N-polar, and NWs cannot grow on III-polar nitride epilayers. On the other hand, we have already reported that the AlN islands formed after the aluminization process are N-polar, while the AlN films directly grown on β-Si3N4 are Al-polar [10]. At the beginning of AlN NW growth, the bare Si (111) surface between AlN islands is unintentionally nitridated to form β-Si3N4. Then, based on this β-Si3N4, Al-polar AlN films are formed because the Al adatoms prefer to react with active N radicals rather than β-Si3N4. In order to examine the polarities of the AlN NWs and island-like films, the sample was treated in 10 % KOH solution for 60 s at 80 °C. KOH solution can only etch N-polar AlN, while Al-polar AlN is resistant to KOH [18]. The SEM image of the etched surface is shown in Fig. 8. It can be seen that there are no NWs remaining on the surface but many hexagonal holes which have nearly the same density and average diameter as the AlN NWs, and the island-like films around the holes are not etched, almost keeping the original morphologies. This is a clear evidence that the AlN NWs are N-polar whereas the films are Al-polar. Furthermore, the residuals in the holes resulted from the anisotropic etching rate with respect to different crystalline planes, and some small holes can be attributed to the N-polar inversion domains in the films.Fig. 8

Bottom Line: The influence of growth conditions on the morphologies of AlN NWs is carefully investigated.Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms.Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

View Article: PubMed Central - PubMed

Affiliation: Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. eyx11@mails.tsinghua.edu.cn.

ABSTRACT
By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

No MeSH data available.


Related in: MedlinePlus