Nucleation transition and nucleus density scaling in surfactant-mediated epitaxy

Abstract

A model of submonolayer epitaxial growth mediated by a monolayer of surfactant is studied, where exchange of adatoms with their underneath surfactant atoms is reversible; i.e., an exchanged adatom can reexchange with the lifted surfactant atom to return to the top of the surfactant layer when the substrate temperature is high enough. A rate equation analysis shows that island nucleation governed by the reexchanging-controlled surface diffusion obeys a scaling law, which connects the nucleation density with the rates of the deposition, surface diffusion, exchange, and reexchange process. Our model system reveals distinct nucleation transitions due to the activated exchange and reexchange, and the nucleation density as a function of temperature exhibits a characteristic N shape with a minimum and a maximum, which define the transition temperatures. The analytical results are confirmed by comparison with kinetic Monte Carlo simulations.

Thermal defect healing of single-walled carbon nanotubes assisted by supplying carbon-containing reactants

“…Among the RBM spectra shown in . Based on previous works, 18,53,54) low formation energy of vacancy and 5|7 defects appears in the SWCNTs with small diameter, which eases the formation of these types of defects in the SWCNTs with small diameter. Healing of thin SWCNTs with higher density of defects, especially the vacancy defect, would take longer time compared with thick SWCNTs.…”

“…Among such defects, the low formation energy of adatom defect makes it easy to be constructed. 53) Thus, compared to the adatom defects, the vacancy defects in the pristine SWCNT structure appear with lower density because of their high formation energy. 53) Besides, related to the diameter of SWCNTs, the formation energy of defects is lower in the SWCNTs with small diameter compared with the one with large diameter, 18,54) which makes vacancy defects easier to form on the thin SWCNTs.…”

A Review on 1‐D Nanomaterials: Scaling‐Up with Gas‐Phase Synthesis

“…The hydrogen reduces the partially oxidized particles to pure metal form; however, H 2 also maintains health of the activated catalyst, being prone to poisoning from parallel soot generation [325] . It is also known that the polycyclic ring formation involved in CNTs germinating from the catalyst nanoparticles can suffer from defects during growth, whereby H 2 drives a healing mechanism [326] . It should be noted that hydrogen may also play the role of functionalizing the CNTs (i. e. doping), which can result from the use of plasma‐enhanced conditions [327] – however, this exceeds the role of additive defined here.…”

Simulation of 3-dimensional Morphology on Different Substrates of Thin Film Growth

“…Surface migration is modeled as a nearest-neighbor hopping process, with the hopping rate of an Arrehnius form: When the substrate are pre-covered with certain covrage of surfactant atoms in some metal or semiconductor surface. The exchange process will happen when a diffusing adatom is just on top of a surfactant atom and can overcome the exchange barrier ex E , it will be dropped to the beneath site, on the other hand, the surfactant atom will be lifted to the above site,with the rate of an Arrehnius form [15]:…”