How "hot precursors" modify island nucleation: A rate-equations model

TL;DR

This paper introduces a new model for island nucleation that accounts for transient ballistic mobility of hot precursors, revealing complex scaling behaviors and fitting experimental data well.

Contribution

It presents a novel rate-equations model incorporating hot precursor mobility, bridging diffusive and ballistic regimes in island nucleation.

Findings

Derived exact scaling laws for island density in different regimes.

Identified complex intermediate behaviors between ballistic and diffusive limits.

Successfully fitted experimental organic-molecule deposition data.

Abstract

We propose a novel island nucleation and growth model explicitly including transient (ballistic) mobility of the monomers deposited at rate $F$, assumed to be in a hot precursor state before thermalizing. In limiting regimes, corresponding to fast (diffusive) and slow (ballistic) thermalization, the island density $N$ obeys scaling $N \propto F^\alpha$. In between is found a rich, complex behavior, with various distinctive scaling regimes, characterized by effective exponents $\alpha_{\rm eff}$ and activation energies that we compute exactly. Application to $N(F,T)$ of recent organic-molecule deposition experiments yields an excellent fit.