Characterizing Submonolayer Growth of 6P on Mica: Capture Zone Distributions vs. Growth Exponents and the Role of Hot Precursors*

Analyzing capture-zone distributions (CZD) using the generalized Wigner distribution (GWD) has proved a powerful way to access the critical nucleus size $i$.\footnote{TLE, AP, Diego Luis Gonz\'alez, J. Cryst. Growth 401, 67 (2014)} Of the several systems to which the GWD has been applied, we consider 6P on mica, for which Winkler's group found $i \approx 3$. Subsequently they measured the growth exponent $\alpha$ (island density $\propto F^\alpha$, for flux $F$) of this system and found good scaling but different values at small and large $F$, which they attributed to DLA and ALA dynamics, but with larger values of $i$ than found from the CZD analysis. We investigate this result in some detail. The third talk of this group describes a new universal relation between $\alpha$ and the characteristic exponent $\beta$ of the GWD. The second talk reports the results of a proposed model that takes long-known transient ballistic adsorption into account, for the first time in a quantitative way.\footnote{JRM-C, TLE, \& AP, PRL, in press} We find several intermediate scaling regimes, with distinctive values of $\alpha$ and an effective activation energy. One of these, rather than ALA, gives the best fit of the experimental data and a value of $i$ consistent with the CZD analysis.