Independent Control of Nucleation and Layer Growth in Nanowires

Abstract

Control of the crystallization process is central to developing novel materials with atomic precision to meet the demands of electronic and quantum technology applications.Semiconductor nanowires grown by the vapor-liquid-solid process are a promising material system in which the ability to form components with structure and composition not achievable in bulk is well-established. Here we use in situ TEM imaging of GaAs nanowire growth to understand the processes by which the growth dynamics are connected to the experimental parameters. We find that two sequential steps in the crystallization processnucleation and layer growthcan occur on similar time scales and can be controlled independently using different growth parameters. Importantly, the layer growth process contributes significantly to the growth time for all conditions, and will play a major role in determining material properties. The results are understood through theoretical simulations correlating the growth dynamics, liquid droplet and experimental parameters.A central challenge in crystal growth is to understand the dynamic and transient processes underlying the nucleation and growth steps. The ability to independently control these two steps would greatly expand the potential to design the structure, morphology and properties of the resulting material. Understanding the steps in crystallization is particularly important in

Growth of GaAs nanowire–graphite nanoplatelet hybrid structures

“…Evidently, the values of interface energies and depend on the composition of the liquid phase. The AuGa catalyst of 70% of gold and 30% of gallium was observed in the in-situ Xray energy dispersive spectroscopic measurements during the Au-catalyzed growth of GaAs NWs at the temperatures similar to our growth temperature 53 . For the aforesaid composition of liquid catalyst = 0.13 J/m² and = 0.15 J/m² - 51 .…”

“…Figure 3a illustrates the transformation of planar NW growing on GNP into inclined NW at the edge of oxide surface described by our model. As mentioned before, we consider the AuGa catalyst, which consists of 70% of gold and 30% of gallium 53 . However, the composition of the catalyst is known to be sensitive to both growth temperature and precursor fluxes 53,54 .…”

“…As mentioned before, we consider the AuGa catalyst, which consists of 70% of gold and 30% of gallium 53 . However, the composition of the catalyst is known to be sensitive to both growth temperature and precursor fluxes 53,54 . Thus, our analysis should be extended to the cases of different Au content in the catalyst.…”

Oscillations of As Concentration and Electron-to-Hole Ratio in Si-Doped GaAs Nanowires

“…As discussed in detail in Reference [ 29 ], the main contribution to is logarithmic [ 3 , 32 , 33 ], and it can be put as . Here, we present the As concentration in a catalyst droplet in terms of the effective coverage equivalent to the arsenic content in liquid, denoted , by normalizing the total number of As atoms in liquid to the number of As atoms (or GaAs pairs) in the full ML of a GaAs NW.…”

“…The growth rates can be much faster in vapor phase deposition techniques, reaching approximately 15 ML/s in the extreme case of Au-catalyzed GaAs NWs in hydride vapor phase epitaxy (HVPE) [ 31 ]. Such a huge difference (approximately 100 times) does not guarantee that the strong inequality is satisfied in the entire range of possible VLS growth conditions (separation of the ML nucleation, growth, and refill has recently been investigated in Reference [ 32 ] from a different perspective). Here, we investigate theoretically self-regulated oscillations of group V concentration in a catalyst droplet during the VLS growth of III–V NWs and their impact on the Si doping of GaAs NWs in the general case without the time-scale separation of the ML growth and refill.…”