Quantitative results from observations of two-dimensional nucleation in NaCl crystal growth

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The electron microscopic gold decoration technique was used to investigate the growth mode of random two-dimensional nucleation in vapour deposition of NaCl. By evaluating step patterns consisting of islands which were produced by the formation and spreading of the two-dimensional nuclei, it was possible to determine quantities which are interesting for discussing phenomena of crystal growth: the condensation coefficient β≤1 depending on the step density, the density of nuclei N ∗=2×10 8−5×10 10cm −2 depending on the supersaturation δμ=kT ln( R R O ) , the step velocity υ=2−50 nm s −1 depending on the evaporation rate R, and the quantity 1 Q ≈ 100 nm characterizing the mean surface diffusion length.