We report high-resolution surface morphology and friction force maps of polycrystalline organic thin films derived by deposition of the n-type perylene diimide semiconductor PDI8-CN₂. We show that the in-plane molecular arrangement into ordered, cofacial slip-stacked rows results in a largely anisotropic surface structure, with a characteristic sawtooth corrugation of a few Ångstroms wavelength and height. Load-controlled experiments reveal different types of friction contrast between the alternating sloped and stepped regions, with transitions from atomic-scale dissipative stick–slip to smooth sliding with ultralow friction within the surface unit cell. Notably, such a rich phenomenology is captured under ambient conditions. We demonstrate that friction contrast is well reproduced by numerical simulations assuming a reduced corrugation of the tip–molecule potential nearby the step edges. We propose that the side alkyl chains pack into a compact low-surface-energy overlayer, and friction modulation reflects periodic heterogeneity of chains bending properties and subsurface anchoring to the perylene cores.

中文翻译：

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Conditions条件下of二酰亚胺PDI8-CN ₂薄膜表面的亚纳米分辨率和增强的摩擦对比度

我们报告通过沉积n型per二酰亚胺半导体PDI8-CN ₂衍生的多晶有机薄膜的高分辨率表面形态和摩擦力图。我们显示面内分子排列成有序的，界面滑移堆积的行会导致很大程度上是各向异性的表面结构，并具有几埃波长和高度的特征性锯齿状波纹。载荷控制实验揭示了交替变化的倾斜区域和阶梯区域之间的不同类型的摩擦反差，从原子尺度的耗散粘滑转变为表面单元内具有超低摩擦的平滑滑动。值得注意的是，这种丰富的现象学是在环境条件下捕获的。我们证明，通过数值模拟可以很好地再现摩擦衬度，前提是假设台阶边缘附近的尖端分子势能减少了波纹。我们建议将烷基侧链堆积成紧凑的低表面能覆盖层，