We conducted atomic force microscopy (AFM) experiments by sliding hard tetrahedral amorphous carbon (ta-C)-coated and diamond AFM probes against silicon oxide-doped hydrogenated amorphous carbon (a-C:H:Si:O) films. We reproducibly observe a substantial reduction in friction with repeated sliding. This behavior qualitatively resembles the run-in effects generally seen in macroscale frictional sliding on diamond-like carbons (DLCs), including this a-C:H:Si:O film in particular. As the applied normal load is increased with repetitive sliding, the friction reduces in tandem. The lateral stiffness of the nanoscale contact is measured as a function of applied normal load, thus the real contact area and the interfacial shear strength are inferred throughout the sliding experiments. These measurements show that the friction reduction is caused by a reduction in the interfacial shear strength of the contact. We propose that this arises from sliding-induced structural modification of the a-C:H:Si:O film. The calculated shear strengths are more than an order of magnitude higher than estimates from macroscale friction experiments. Additionally, humidity-controlled experiments show no significant humidity dependence of the friction despite a very strong dependence at macroscale. Reasons for these contradictions with macroscale experiments are discussed.

中文翻译：

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纳米氧化硅掺杂氢化非晶碳的磨合：界面剪切强度对滑动长度和湿度的依赖性

我们通过将硬四面体无定形碳（ta-C）涂层和金刚石AFM探针滑动到掺杂氧化硅的氢化无定形碳（aC：H：Si：O）膜上，进行了原子力显微镜（AFM）实验。我们可重复地观察到反复滑动会大大降低摩擦。这种行为在质量上类似于在类金刚石碳（DLC）上进行大规模摩擦滑动时通常看到的磨合效果，尤其是在这种aC：H：Si：O薄膜上。随着施加的法向载荷随着重复滑动而增加，摩擦随之减小。纳米级接触的横向刚度是所施加法向载荷的函数，因此在整个滑动实验中可以推断出实际接触面积和界面剪切强度。这些测量结果表明，摩擦的减小是由于接触件的界面剪切强度的降低引起的。我们认为，这是由于aC：H：Si：O薄膜的滑动诱导结构改性引起的。计算出的剪切强度比宏观摩擦实验的估计值高出一个数量级。此外，湿度控制的实验表明，尽管在宏观上有很强的依赖性，但摩擦对湿度的依赖性并不明显。讨论了与宏观实验产生这些矛盾的原因。此外，湿度控制的实验表明，尽管在宏观上有很强的依赖性，但摩擦对湿度的依赖性并不明显。讨论了与宏观实验产生这些矛盾的原因。此外，湿度控制的实验表明，尽管在宏观上有很强的依赖性，但摩擦对湿度的依赖性并不明显。讨论了与宏观实验产生这些矛盾的原因。