Atomic-Scale Observation of Vapor–Solid Nanowire Growth <i>via</i> Oscillatory Mass Transport

<i>In situ</i> atomic-scale transmission electron microscopy (TEM) can provide critical information regarding growth dynamics and kinetics of nanowires. A catalyst-aided nanowire growth mechanism has been well-demonstrated by this method. By contrast, the growth mechanism of nanowires without catalyst remains elusive because of a lack of crucial information on related growth dynamics at the atomic level. Herein, we present a real-time atomic-scale observation of the growth of tungsten oxide nanowires through an environmental TEM. Our results unambiguously demonstrate that the vapor–solid mechanism dominates the nanowire growth, and the oscillatory mass transport on the nanowire tip maintains the noncatalytic growth. Autocorrelation analysis indicates that adjacent nucleation events in the nanowire growth are independent of each other. These findings may improve the understanding of the vapor–solid growth mechanism of nanowires.