Abstract:In this study, we demonstrate that by merely limiting the As flux, the growth behavior and structural quality of Au-catalyzed GaAs nanowires can be modulated in molecular beam epitaxy. With decreasing the As flux through lowering the V/III ratio, GaAs nanowire growth is found to be slow and defect-free wurtzite structured GaAs nanowires can be obtained regardless of catalyst sizes. While, in the As-enrich environment (such as at relatively high V/III ratio), thinner nanowires can grow longer with fewer planar … Show more
“…To understand this difference, we note that both studies employed different P/ III ratios. Our early study 34 indicates the growth rate of nanowires can be limited by the group V sources. In the case of InGaP nanowires grown by MBE, short nanowires were grown in which sufficient In can diffuse into catalysts, resulting in Inenriched nanowire cores.…”
In this study, we report the growth of core− shell InGaP nanowires with compositional varied cores/shells using metal−organic chemical vapor deposition. These core− shell InGaP nanowires exhibit Ga-enriched cores attributed to the strong affinity between Au and In, and In-enriched shells due to In-rich vapor ambient. Detailed electron microscopy investigations indicate that the In and Ga concentrations in the nanowire cores and shells varied along the growth direction of InGaP nanowires. It is found that the strain relaxation through Ga diffusion outward and In diffusion inward leads to the decrease of compositional difference between the nanowire core and shell from top to bottom. This study offers a possibility to grow structural complex ternary nanowires that can be used for future applications.
“…To understand this difference, we note that both studies employed different P/ III ratios. Our early study 34 indicates the growth rate of nanowires can be limited by the group V sources. In the case of InGaP nanowires grown by MBE, short nanowires were grown in which sufficient In can diffuse into catalysts, resulting in Inenriched nanowire cores.…”
In this study, we report the growth of core− shell InGaP nanowires with compositional varied cores/shells using metal−organic chemical vapor deposition. These core− shell InGaP nanowires exhibit Ga-enriched cores attributed to the strong affinity between Au and In, and In-enriched shells due to In-rich vapor ambient. Detailed electron microscopy investigations indicate that the In and Ga concentrations in the nanowire cores and shells varied along the growth direction of InGaP nanowires. It is found that the strain relaxation through Ga diffusion outward and In diffusion inward leads to the decrease of compositional difference between the nanowire core and shell from top to bottom. This study offers a possibility to grow structural complex ternary nanowires that can be used for future applications.
“…Moreover, in Au droplets, the Ga concentration increases exponentially with the decrease of the diameter. Ga solubility reaches 40% for 20 nm diameter droplets [35,36], which contributes to maintaining a high group III concentration (and supersaturation) in the catalyst. Thus, the GaAs nanowires keep growing in the wurtzite crystal structure, forming sharp edge facets at the liquid-solid interface.…”
Section: Influence Of the Growth Parameters On The Morphology Of Inas...mentioning
We report on the growth of axial InAs-on-GaAs nanowire heterostructures on silicon by molecular beam epitaxy using 20 nm diameter Au catalysts. First, the growth parameters of the GaAs nanowire segment were optimized to achieve a pure wurtzite crystal structure. Then, we developed a two-step growth procedure to enhance the yield of vertical InAs-on-GaAs nanowires. We achieved 90% of straight InAs-on-GaAs nanowires by further optimizing the growth parameters. We investigated the composition change at the interface by energy dispersive X-ray spectroscopy and the nanowire crystal structure by transmission electron microscopy. The nominal composition of the InAs segment is found to be In x Ga 1-x As with x=0.85 and corresponds to 6% of lattice mismatch with GaAs. Strain mapping performed by the geometrical phase analysis of high-resolution images revealed a dislocation-free GaAs/In 0.85 Ga 0.15 As interface. In conclusion, we successfully fabricated highly mismatched heterostructures, confirming the prediction that axial GaAs/In 0.85 Ga 0.15 As interfaces are pseudomorphic in nanowires below 40 nm diameter.
“…For the self-catalyzed growth of GaSb nanowires, the effective supersaturation Δ μ is dominated by the concentration of Sb atoms incorporated in the Ga catalytic droplets. Therefore, the effective supersaturation Δ μ can be presented as [32, 33]Fig. 3Statistical data of the diameter and length of the GaSb nanowires grown at 500 and 520 °C.
…”
We report the first self-catalyzed growth of high-quality GaSb nanowires on InAs stems using metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates. To achieve the growth of vertical InAs/GaSb heterostructure nanowires, the two-step flow rates of the trimethylgallium (TMGa) and trimethylantimony (TMSb) are used. We first use relatively low TMGa and TMSb flow rates to preserve the Ga droplets on the thin InAs stems. Then, the flow rates of TMGa and TMSb are increased to enhance the axial growth rate. Because of the slower radial growth rate of GaSb at higher growth temperature, GaSb nanowires grown at 500 °C exhibit larger diameters than those grown at 520 °C. However, with respect to the axial growth, due to the Gibbs-Thomson effect and the reduction in the droplet supersaturation with increasing growth temperature, GaSb nanowires grown at 500 °C are longer than those grown at 520 °C. Detailed transmission electron microscopy (TEM) analyses reveal that the GaSb nanowires have a perfect zinc-blende (ZB) crystal structure. The growth method presented here may be suitable for other antimonide nanowire growth, and the axial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2207-5) contains supplementary material, which is available to authorized users.
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