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Effect of growth temperature on the morphology and phonon properties of InAs nanowires on Si substrates.

Li T, Chen Y, Lei W, Zhou X, Luo S, Hu Y, Wang L, Yang T, Wang Z - Nanoscale Res Lett (2011)

Bottom Line: It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics.A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction.A splitting of TO modes is also observed.PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Material Science, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083, People's Republic of China. yhchen@semi.ac.cn.

ABSTRACT
Catalyst-free, vertical array of InAs nanowires (NWs) are grown on Si (111) substrate using MOCVD technique. The as-grown InAs NWs show a zinc-blende crystal structure along a < 111 > direction. It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics. The longitudinal optical and transverse optical (TO) mode of InAs NWs present a phonon frequency slightly lower than those of InAs bulk materials, which are speculated to be caused by the defects in the NWs. A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction. The carrier concentration is extracted to be 2.25 × 1017 cm-3 from the Raman line shape analysis. A splitting of TO modes is also observed.PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km.

No MeSH data available.


Raman spectra of InAs NWs recorded parallel and perpendicular to the c-axis. (a) Raman spectra of as-grown vertical aligned InAs NWs (sample B) recorded in backscattering geometry parallel to the c-axis, (b) Raman spectra of InAs NWs recorded perpendicular to the c-axis of nanowires. Excitation laser power 0.25 mW, the lighter colored (green) lines are results from a multiple Lorentzian fit.
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Figure 4: Raman spectra of InAs NWs recorded parallel and perpendicular to the c-axis. (a) Raman spectra of as-grown vertical aligned InAs NWs (sample B) recorded in backscattering geometry parallel to the c-axis, (b) Raman spectra of InAs NWs recorded perpendicular to the c-axis of nanowires. Excitation laser power 0.25 mW, the lighter colored (green) lines are results from a multiple Lorentzian fit.

Mentions: Figure 4 shows the Raman spectra of InAs NWs with a diameter of 42 nm (sample B) measured with the incident laser beam both parallel and perpendicular to the c-axis of NWs. Note that the laser excitation power used for measuring Raman spectra in Figure 4 is 0.25 mW. Compared with the TO peak measured with incident laser beam parallel to c-axis of NWs, the TO peak measured with incident laser beam perpendicular to c-axis of NWs shifts to lower frequency with asymmetric broadening, where a weak shoulder peak appears at the lower energy side of TO mode. This indicates a possible splitting of TO mode, giving rise to A1 (TO) mode reported [31]. A more detailed study on the splitting as a function of the NW crystal structure, strain, diameter, and length is currently under way.


Effect of growth temperature on the morphology and phonon properties of InAs nanowires on Si substrates.

Li T, Chen Y, Lei W, Zhou X, Luo S, Hu Y, Wang L, Yang T, Wang Z - Nanoscale Res Lett (2011)

Raman spectra of InAs NWs recorded parallel and perpendicular to the c-axis. (a) Raman spectra of as-grown vertical aligned InAs NWs (sample B) recorded in backscattering geometry parallel to the c-axis, (b) Raman spectra of InAs NWs recorded perpendicular to the c-axis of nanowires. Excitation laser power 0.25 mW, the lighter colored (green) lines are results from a multiple Lorentzian fit.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211884&req=5

Figure 4: Raman spectra of InAs NWs recorded parallel and perpendicular to the c-axis. (a) Raman spectra of as-grown vertical aligned InAs NWs (sample B) recorded in backscattering geometry parallel to the c-axis, (b) Raman spectra of InAs NWs recorded perpendicular to the c-axis of nanowires. Excitation laser power 0.25 mW, the lighter colored (green) lines are results from a multiple Lorentzian fit.
Mentions: Figure 4 shows the Raman spectra of InAs NWs with a diameter of 42 nm (sample B) measured with the incident laser beam both parallel and perpendicular to the c-axis of NWs. Note that the laser excitation power used for measuring Raman spectra in Figure 4 is 0.25 mW. Compared with the TO peak measured with incident laser beam parallel to c-axis of NWs, the TO peak measured with incident laser beam perpendicular to c-axis of NWs shifts to lower frequency with asymmetric broadening, where a weak shoulder peak appears at the lower energy side of TO mode. This indicates a possible splitting of TO mode, giving rise to A1 (TO) mode reported [31]. A more detailed study on the splitting as a function of the NW crystal structure, strain, diameter, and length is currently under way.

Bottom Line: It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics.A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction.A splitting of TO modes is also observed.PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Material Science, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083, People's Republic of China. yhchen@semi.ac.cn.

ABSTRACT
Catalyst-free, vertical array of InAs nanowires (NWs) are grown on Si (111) substrate using MOCVD technique. The as-grown InAs NWs show a zinc-blende crystal structure along a < 111 > direction. It is found that both the density and length of InAs NWs decrease with increasing growth temperatures, while the diameter increases with increasing growth temperature, suggesting that the catalyst-free growth of InAs NWs is governed by the nucleation kinetics. The longitudinal optical and transverse optical (TO) mode of InAs NWs present a phonon frequency slightly lower than those of InAs bulk materials, which are speculated to be caused by the defects in the NWs. A surface optical mode is also observed for the InAs NWs, which shifts to lower wave-numbers when the diameter of NWs is decreased, in agreement with the theory prediction. The carrier concentration is extracted to be 2.25 × 1017 cm-3 from the Raman line shape analysis. A splitting of TO modes is also observed.PACS: 62.23.Hj; 81.07.Gf; 63.22.Gh; 61.46.Km.

No MeSH data available.