The nucleation and growth of organic molecules is usually discussed in the framework of diffusion limited aggregation (DLA). In this letter we demonstrate for the rod-like organic molecules hexaphenyl (6P) on sputter-modified mica, that under specific experimental conditions the nucleation has to be described by attachment limited aggregation (ALA). The crucial parameter for the growth mode is the roughness of the substrate surface, as induced by ion sputtering. With decreasing surface roughness the diffusion probability of the molecules increases and the growth mode changes from DLA to ALA. This was derived from the deposition rate dependence of the island density. A critical size of i = 7 molecules was determined for the nucleation of 6P on a moderately sputtered mica surface.

中文翻译：

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有机分子的附着限制与扩散限制成核：溅射改性云母上的六苯基

有机分子的成核和生长通常在扩散限制聚集 (DLA) 的框架中讨论。在这封信中，我们证明了溅射改性云母上的棒状有机分子六苯基 (6P)，在特定实验条件下，必须通过附着限制聚集 (ALA) 来描述成核。生长模式的关键参数是由离子溅射引起的衬底表面的粗糙度。随着表面粗糙度的降低，分子的扩散概率增加，生长模式从 DLA 变为 ALA。这是源自岛密度的沉积速率依赖性。对于 6P 在适度溅射的云母表面上的成核，确定了 i = 7 分子的临界尺寸。