Abstract

The influences of droplet size on the growth of self-catalyzed ternary nanowires (NWs) were studied using GaAsP NWs. The size-induced Gibbs-Thomson (GT) effect makes the smaller catalytic droplets have lower effective supersaturations and hence slower nucleation rates than the larger ones. Large variation in droplet size thus led to the growth of NWs with low uniformity, while a good size uniformity of droplets resulted in the production of highly uniform NWs. Moreover, thinner NWs were observed to be richer in P, indicating that P is more resistant to the GT effect than As because of a higher chemical potential inside Ga droplets. These results provide useful information for understanding the mechanisms of self-catalyzed III-V NW nucleation and growth with the important ternary III-V material systems.

Highlights

  • The research on III−V nanowires (NWs) has intensified over the last two decades due to their potential use in electronic and optoelectronic devices.[1−3] Their one-dimensional geometry at nanometer scale can lead to different crystallographic,[4,5] photonic,[6−8] electrical,[9,10] and mechanical[11] properties than those of their thin film counterparts

  • Catalytic droplets are needed to achieve the vapor−liquid−solid (VLS) growth,[16] which is significantly different from the traditional thin film growth using the vapor−solid mode

  • The influences caused by the small droplet size can greatly affect the NW growth and modify the performances of the reactants.[17]

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Summary

Nano Letters

When using the NWs for the device fabrication after growth, a good NW uniformity is favorable, because it can greatly facilitate the fabrication process and reduce the cost. With the increase of the growth temperature to ∼645 °C, the size distribution of NWs did not change significantly, as can be seen in the inset of Figure 3e This can boost sidewall material collection and the growth rate difference between long (thick) and short (thin) NWs. According to the above observations, the model proposed in Figure 4 could explain the large variation in NW length and diameter during the growth of GS-GaAsP NWs. At the beginning of the GaAs stem growth, there was no material deposition on the substrate surface, which is beneficial for the formation of droplets with uniform diameters.

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