Nano-indentation of thin films on materials surface

我们构建了一台先进的纳米压痕测试仪，用于评估材料表面在10 nm深度内的力学性能。利用该仪器，我们检测了基片玻璃、薄膜硬盘和铁氧体磁头等各种材料。采用三维有限元方法对计算结果进行分析。主要研究成果如下：(A)对Berkovich三棱柱压头纳米压痕的弹性行为进行了三维有限元分析。提出了考虑尖端截断影响的Berkovich压痕载荷与位移之间的理论关系。(B)研制了载荷为0.1微N、位移分辨率为0.1 nm的纳米压痕测试仪。在位移控制条件下操作时，该仪器能够检测压头尖端与样品表面的接触，精度为0.2 nm。(C)使用5 nm截断的Berkovich尖端检测了仅深度为5 nm的衬底玻璃的纳米压痕行为。我们发现，当尖端下的米塞斯应力达到玻璃的理论强度时，就会发生塑性变形。(D)利用纳米压痕实验估算了薄膜刚性盘上覆层膜的杨氏模数。对磁记录头滑块表面的机械研磨表面损伤进行了评估。

We constructed an advanced nanoindentation tester to evaluate the mechanical property of materials surface in the depth as small as 10nm. Using this instrument, we examined various materials such as substrate glass, thin film rigid disks and ferrite heads. The results were analyzed by the three-dimensional finite element method (FEM). The main research results obtained are as follows.(a) Three-demensional analysis by FEM was conducted on the elastic behavior of nanoindentation with a Berkovich triangular prismatic indenter. We proposed a theoretical relationship between applied load and displacement for the Berkovich indentation, including the effect of the tip truncation.(b) We developed a nanoindentation tester with 0.1muN load and 0.1nm displacement resolutions. The instrument was capable of detecting contact of the indenter tip with the sample surface with the accuracy of 0.2nm when operated under displacement controlled conditions.(c) The nanoindentation behavior of a substrate glass to a depth only 5nm was examined using an 5nm truncated Berkovich tip. We found that the plastic deformation initiated when the Mises stress underneath the tip attained the theoretical strength of glass.(d) The nanoindentation test was applied to estimate the Young's modulus of overcoat films on the thin film rigid disks. The damage of surface finishing by mechanical lapping was also evaluated for the slider surface of magnetic recording heads.