Higher Compressive Strengths and Bauschinger Effect in Conformally-Passivated Copper Nanopillars.
Higher Compressive Strengths and Bauschinger Effect in Conformally-Passivated Copper Nanopillars.
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DOI：
10.1016/j.actamat.2012.03.013
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发表时间：
2012-02
期刊：
影响因子：
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通讯作者：
C. Weinberger;J. Greer;F. Greer;A. Jennings;C. Gross;Z. Aitken;S. Lee
中科院分区：
文献类型：
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作者：
C. Weinberger;J. Greer;F. Greer;A. Jennings;C. Gross;Z. Aitken;S. Lee
我们目前对纳米和微尺度晶体中尺寸依赖性强度的理解是围绕着这样一种观点，即总体强度是由传播位错源所需的应力决定的。这些位错源的性质和类型是广泛争论的主题，然而，这些理论的一个共同点是，自由表面吸收位错的能力是过渡到源控制状态的必要条件。在这项工作中，我们证明了在直径为75nm至1μm的电镀单晶铜柱上原子层沉积（ALD） 5-25nm厚的TiO2/ al2o3涂层通常可以抑制位错在自由表面消失的能力。单轴压缩试验表明，在相同直径下，相对于未涂覆的柱，强度和硬化增加，卸载时塑性应变显著恢复，即鲍辛格效应。与之前的报道不同，这些涂层柱在应力-应变曲线中保留了随机特征。我们在基于单臂源模型、位错理论和透射电子显微镜显微结构分析的尺寸依赖强度理论的框架内解释了这些观察结果。
Our current understanding of size-dependent strength in nano- and microscale crystals is centered around the idea that the overall strength is determined by the stress required to propagate dislocation sources. The nature and type of these dislocation sources is the subject of extensive debate, however, one commonality amongst these theories is that the ability of the free surface to absorb dislocations is a necessary condition for transition to a source controlled regime. In this work we demonstrate that atomic layer deposition (ALD) of conformal 5–25nm thick TiO2/Al2O3coatings onto electroplated single crystalline copper pillars with diameters ranging from 75nm to 1μm generally inhibits the ability of a dislocation to vanish at the free surface. Uniaxial compression tests reveal increased strength and hardening relative to uncoated pillars at equivalent diameters, as well as a notable recovery of plastic strain during unloading, i.e. the Bauschinger effect. Unlike previous reports, these coated pillars retained the stochastic signature in their stress–strain curves. We explain these observations within the framework of a size-dependent strength theory based on a single arm source model, dislocation theory, and microstructural analysis by transmission electron microscopy.