The unusual bias-voltage dependence of copper-hexadecafluoro-phthalocyanine (F16CuPc) molecules on Au(111) was investigated by using scanning tunneling microscopy/spectroscopy (STM/STS) at low temperatures. Depending on the bias polarity, the molecules seem to cover the whole surface of Au(111) at positive bias voltages while they are apparently invisible in STM images at negative bias voltages. Here, we experimentally demonstrate that the molecular diffusivity on Au(111) varies according to the applied electric field induced between the STM tip and the Au(111) surface rather than the intrinsic molecule-substrate interaction. Such results are corroborated by STS measurements indicating that attraction/repulsion of a molecule indeed occurs under an STM tip at positive/negative bias voltages during sweeps of the bias voltage. In addition, we found that the diffusive molecules are immobilized at a temperature of 8 K at both positive and negative bias voltages due to a lack of thermal energy for diffusion.

中文翻译：

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铜-十六氟-酞菁分子在 Au(111) 上的异常扩散行为

通过在低温下使用扫描隧道显微镜/光谱 (STM/STS) 研究了铜十六氟酞菁 (F16CuPc) 分子对 Au(111) 的异常偏置电压依赖性。根据偏压极性，分子似乎在正偏压下覆盖了 Au(111) 的整个表面，而在负偏压下它们在 STM 图像中显然不可见。在这里，我们通过实验证明 Au(111) 上的分子扩散率根据 STM 尖端和 Au(111) 表面之间感应的外加电场而不是固有的分子 - 基材相互作用而变化。这些结果由 STS 测量证实，表明在偏置电压扫描期间，分子的吸引/排斥确实发生在 STM 尖端下的正/负偏置电压下。此外，