Regimes of radial growth for Ga-catalyzed GaAs nanowires

Abstract

We present a non-stationary growth model of Ga-catalyzed GaAs nanowires which is based on the two kinetic equations for the nanowire elongation rate and a time-dependent base radius of the droplet. We show that self-catalyzed nanowire growth is principally different from the Au-catalyzed one because a stationary droplet size cannot be maintained at all times. Close examination of the model enables us to separate different regimes of radial growth in which the droplet shrinks, inflates or converges to a certain stationary size as nanowires grow, depending on the initial droplet radius and the growth conditions. We also discuss some experimental data on the growth modes of Ga-catalyzed GaAs nanowires from the viewpoint of the obtained results.

Comparison of GaAs nanowire growth seeded by Ag and Au colloidal nanoparticles on silicon

“…The tops of the NWs were found to be much larger than initial colloidal NPs and, thus, the catalysts are assumed to be Ga-rich during the growth. Therefore, we believe that the diameter stabilization in our experiments is similar to self-equilibration of NW diameters reported previously for self-catalyzed growth [32,33].…”

Radial Growth of Self-Catalyzed GaAs Nanowires and the Evolution of the Liquid Ga-Droplet Studied by Time-Resolved in Situ X-ray Diffraction

“…axial NW heterostructures, 25 and for advanced device applications. [26][27][28] Hence, current efforts aim at the control, 5,7,[29][30][31] and understanding 8,9,[32][33][34][35][36][37][38][39][40][41] of radial growth processes responsible for tapering. Of particular interest here are self-stabilizing growth processes that are closely linked to the liquid Ga-droplet.…”

“…On the one hand, tapering was first regarded as unintended side-effect due to, for example, an inflation of the droplet during growth, as a consequence of unbalanced material fluxes, and its minimization was desired . On the other hand, by harnessing radial growth processes, tapered NWs geometries could be exploited, for example, for axial NW heterostructures, and for advanced device applications. − Hence, current efforts aim at the control ,,− and understanding ,,− of radial growth processes responsible for tapering. Of particular interest here are self-stabilizing growth processes that are closely linked to the liquid Ga-droplet. , In addition to the radial growth processes involving the droplet (VLS), growth at the NW side-walls via the vapor–solid (VS) mode further influences the final shape of the NW ,,,, and impedes the direct observation of the aforementioned self-stabilization processes.…”