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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.


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The NW density, average diameter, and length achieved at different growth temperatures. Solid lines are guides to the eye
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Fig4: The NW density, average diameter, and length achieved at different growth temperatures. Solid lines are guides to the eye

Mentions: Samples E, C, and F were grown at 940, 960, and 980 °C, respectively, with the same aluminization temperature of 900 °C. In our experiments, AlN NWs cannot be obtained at substrate temperatures below 940 °C, and the temperature exceeding 980 °C is limited by the MBE system. The influence of growth temperature on the characteristics of the AlN NWs is shown in Fig. 4. It can be seen that the density and length of AlN NWs tend to increase while the diameter decreases with increasing growth temperature. As Consonni et al. reported [12], the nucleation islands can thermodynamically transform to NWs on critical condition, and higher growth temperature promotes this transformation. At a certain growth temperature, not all of the nucleation islands can transform to NWs, and an increased growth temperature promotes more nucleation islands developing to NWs, hence the NW density increases. However, limited by the total amount of the nucleation islands obtained under a certain aluminization condition, the NW density tends to saturate as shown in Fig. 4. Higher growth temperature also improves Al migration and then increases the amount of Al adatoms that migrate to the top of NWs; therefore, the axial growth rate of NWs increases [13]. Moreover, the incorporation of adatoms on the NW sidewalls is suppressed at higher growth temperature; thus, the radial growth rate decreases. The similar phenomena were also observed in GaN NW growth [14].Fig. 4


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)

The NW density, average diameter, and length achieved at different growth temperatures. Solid lines are guides to the eye
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig4: The NW density, average diameter, and length achieved at different growth temperatures. Solid lines are guides to the eye
Mentions: Samples E, C, and F were grown at 940, 960, and 980 °C, respectively, with the same aluminization temperature of 900 °C. In our experiments, AlN NWs cannot be obtained at substrate temperatures below 940 °C, and the temperature exceeding 980 °C is limited by the MBE system. The influence of growth temperature on the characteristics of the AlN NWs is shown in Fig. 4. It can be seen that the density and length of AlN NWs tend to increase while the diameter decreases with increasing growth temperature. As Consonni et al. reported [12], the nucleation islands can thermodynamically transform to NWs on critical condition, and higher growth temperature promotes this transformation. At a certain growth temperature, not all of the nucleation islands can transform to NWs, and an increased growth temperature promotes more nucleation islands developing to NWs, hence the NW density increases. However, limited by the total amount of the nucleation islands obtained under a certain aluminization condition, the NW density tends to saturate as shown in Fig. 4. Higher growth temperature also improves Al migration and then increases the amount of Al adatoms that migrate to the top of NWs; therefore, the axial growth rate of NWs increases [13]. Moreover, the incorporation of adatoms on the NW sidewalls is suppressed at higher growth temperature; thus, the radial growth rate decreases. The similar phenomena were also observed in GaN NW growth [14].Fig. 4

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