Young’s modulus measurements on ultra-thin coatings
Young’s modulus measurements on ultra-thin coatings
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超薄涂层的杨氏模量测量
DOI：
10.1557/jmr.2004.19.1.301
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发表时间：
2004
影响因子：
2.7
通讯作者：
F. Richter
中科院分区：
文献类型：
--
作者：
T. Chudoba;M. Griepentrog;A. Dück;D. Schneider;F. Richter
随着超薄薄膜应用的日益广泛，超薄涂层力学性能的测定也变得越来越重要。然而，尽管现有的测量技术有所改进，但对厚度低至几纳米的涂层进行准确的机械测试仍然是一个挑战。纳米压痕是一种常用的机械纳米探头。采用传统的Berkovich尖头测试方法，随着薄膜厚度的减小，会出现衬底对测试结果影响的问题。因此，测量厚度小于100-200 nm的薄膜的模数几乎是不可能的。这个问题可以通过使用球面压头和涂层系统赫兹接触的解析解相结合来解决。它允许从化合物的载荷-位移曲线中分离薄膜和基材的性质。压痕测量是在44 nm的TiN薄膜和厚度在4.3 nm到125 nm之间的类金刚石碳膜上进行的。经过多次修正，得到了高精度的全弹力-位移曲线。更详细地展示了如何使用零点和热漂移校正来获得小于0.2 nm的统计深度误差。第二种方法是基于超声表面波的激光-声学测量，该方法也测量了该厚度范围内的杨氏模数。虽然压痕技术是一种局部探头，而激光-声学技术给出了表面范围为几毫米的积分值，但对于所调查的样品，结果符合得很好。相比之下，用Berkovich压痕仪进行传统的压痕测量，即使是在超低载荷下，也不可能得到正确的杨氏模数结果。
The determination of the mechanical properties of ultra-thin coatings has become more and more important because of the increasing number of applications using such films. However, an accurate mechanical testing of coatings with a thickness down to some nanometers is still a challenge, despite the improvements of existing measurement techniques. Nanoindentation is an often used mechanical nanoprobe. Using the conventional test method with a sharp Berkovich indenter, the problem of the influence of the substrate on the results arises with decreasing film thickness. Therefore, it is nearly impossible to measure the modulus of films with a thickness less than 100–200 nm. The problem can be overcome by using spherical indenters in combination with an analytical solution for the Hertzian contact of coated systems. It allows a separation of film and substrate properties from the load–displacement curve of the compound. Indentation measurements were done at a 44 nm TiN film and at diamondlike carbon coatings in the thickness range between 4.3 nm and 125 nm on Si substrates. Several corrections were applied to obtain wholly elastic force–displacement curves with high accuracy. It is shown in more detail how zero point and thermal drift corrections are used to obtain statistical depth errors below 0.2 nm. Laser-acoustic measurements based on ultrasonic surface waves were chosen as a second method, which also measures the Young’s modulus in this thickness range. Although the indentation technique is a local probe and the laser-acoustic technique gives an integrated value for a surface range of some millimeters, the results agree well for the investigated samples. In contrast, it was impossible to get the correct Young’s modulus results by conventional indentation measurements with Berkovich indenter, even for ultra-low loads.