Geometry controlled transition between tip and root growth in Au catalyzed SnO2 nanowires

Understanding the growth mechanism of metal oxide nanowires remains challenging due to the complex interplay between catalyst phase behavior, interfacial energetics, and mass transport. Here, we propose a framework for understanding SnO2 nanowire growth by elucidating the coexistence and transition between tip-growth and root-growth-dominated vapor liquid solid (VLS) mechanisms. vapor liquid solid (VLS) mechanisms. By engineering catalyst configurations using Au nanoparticles, Au thin films, and hybrid structures, we establish a direct correlation between catalyst geometry and nanowire morphology. The nanowires exhibit a highly crystalline rutile SnO2 phase with lattice parameters (a = 4.74 Å, c = 3.19 Å). High-resolution TEM confirms single-crystalline structures with interplanar spacings of 0.34 nm corresponding to (-1-10) planes. The morphology strongly depends on catalyst configuration, with diameters ranging from 20 nm to 5μm and lengths ranging from 1 μm to over 100 μm . XPS analysis reveals that the Sn2+ fraction increases from 38.0% to 57.3%, suggesting an increasingly oxygen-deficient surface chemical environment associated with catalyst-driven growth kinetics . COMSOL simulations are used to estimate Sn vapor transport and provide order of magnitude agreement with nanowire lengths of 8.9 μm (α = 1.5), consistent with experimental observations. Regulating the transition between tip and root growth regimes, providing a conceptual framework where interfacial effects and catalyst geometry are considered as additional factors beyond conventional supersaturation considerations .