Seminar - Guided Nanowire Growth Kinetics and Mechanism: Surface Matters
23. 10. 2019 (Wednesday) - 14:00
FME A2/201, Technická 2
Amnon Rothman (Weizmann Institute of Science, Israel)
The increasing research of nanowires (NWs) as building blocks for electronic, optoelectronic, energy devices and quantum computing is driven by the unique physical, and chemical properties originate from their nanoscale dimensionality. Catalyzed surface-guided NWs offer the possibility to control their position, direction and crystallographic orientation, which eventually leads to high-performance devices. To adequately control these features and gain predictive abilities, a deeper understanding of the growth mechanism of surface-guided NWs is required. Here, we experimentally and theoretically study the kinetics of planar catalyzed NWs. We present a model that considers two main regimes of the growth rate of NWs depending on their thickness: the Gibbs–Thompson regime, which dominates the growth of thinner NWs, and the surface-diffusion-induced regime, which dominates the growth of thicker ones. By developing this kinetic model and fitting it to the experimental kinetic data, we determine the dimensionality of the surface diffusion. We observe a good correlation between the model and the results for surface-guided ZnSe and ZnS NWs grown on sapphire. The dimensionality of the surface diffusion value was determined to be ~1.5 and ~1.8 for ZnSe and ZnS NWs, respectively, in contrast to the value of 1 for vertical NWs growth models, supporting the difference between the two growth morphologies. The newly developed model distinguishes between the growth mechanisms of horizontal and vertical NWs, underscores the important role of the substrate in the horizontal growth, and provides new insights into the mechanism of surface-guided NWs growth. Understanding the growth mechanism introduces the possibility of controlling the growth directions and crystallographic orientations of the aligned NWs accurately and helps gain some prediction abilities of the NWs properties, leading to better nanowire-based electronic and optoelectronic devices.