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首页> 外文期刊>Physical Review X >Temperature Activates Contact Aging in Silica Nanocontacts
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Temperature Activates Contact Aging in Silica Nanocontacts

机译：温度激活二氧化硅纳米接触的接触老化

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Understanding the time evolution of contact strength in silica nanocontacts is of great fundamental and practical relevance in diverse areas like earthquake dynamics, wafer bonding mechanisms, as well as MEMS applications. The logarithmic increase of contact strength with hold time, termed contact aging, can be “quantitative” due to deformation creep in plastic contacts. An alternative mechanism, termed “qualitative aging,” is the gradual change in interfacial chemistry, which so far was only observed in the presence of humidity. Here we present nanoscale friction experiments of dry silica contacts in ultrahigh vacuum that show a doubling of shear strength with time following a logarithmic law. We find that the aging rate scales linearly with temperature, and that shear stress shifts the relevant energy barriers. All-atom MD simulations provide a live picture of the bond formation dynamics occurring at the interface. Our experiments link contact aging to thermally activated bond formation, show that it exists even in the absence of water molecules, and demonstrate that this atomic aging mechanism can stretch over timescales up to several seconds. Qualitative contact aging is thus highly relevant for a broad variety of material combinations and conditions.
机译：了解二氧化硅纳米接触强度的时间演变是地震动力学，晶圆粘合机制等不同领域的基本和实际相关性，以及MEMS应用。由于塑料触点中的变形蠕变，具有保持时间的接触强度的对数增加，称为接触老化，可以是“定量”。一种替代机制，称为“定性老化”是界面化学的逐渐变化，到目前为止仅在湿度存在下观察到。在这里，我们将纳米级摩擦实验呈现在超高真空中的干式二氧化硅接触，其在对数法之后显示剪切强度的加倍。我们发现老化率随温度线性缩放，并且剪切应力转变相关的能量屏障。 All-Atom MD仿真提供了在界面处发生的键形成动态的实时图片。我们的实验将接触衰老链接到热活化键形成，表明它即使在没有水分子的情况下也存在，并证明该原子老化机构可以在几秒钟内延伸到时间尺寸。因此，定性接触衰老与各种材料组合和条件高度相关。

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