基于原子力显微镜和分子动力学的纳米压痕技术研究

STUDY ON THE NANOINDENTATION VIA ATOMIC FORCE MICROSCOPE AND MOLECULAR DYNAMICS SIMULATION

利用原子力显微镜对真空蒸发镀膜技术制得的单晶铜薄膜试件进行了纳米压痕试验。通过进行各种压痕深度下的试验,获得了压痕深度对试件力学性能的影响关系。试验得到的试件弹性模量为67.0 GPa±6.9 GPa。试件的硬度值随着压痕深度的减小而不断增大,表现出强烈的尺寸效应。在原子力显微镜试验的同时,使用分子动力学仿真方法对单晶铜薄膜的纳米压痕过程进行了研究。仿真结果表明单晶铜薄膜的纳米压痕的力学机理不是位错在晶体中运动产生的塑性变形,而是非晶态产生的变形,从而解释了尺寸效应产生的原因。

Nanoindentation tests performed in an atomic force microscope have been utilized to directly measure the me- chanical properties of single crystal copper thin films fabricated by the vacuum vapor deposition technique. Nanoindentation tests are conduted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The elastic modulus of the single crystal copper film at various indentation depths is determined as 67.0 GPa±6.9 GPa on average which is in reasonable agreement with the results reported in literature. The indentation hardness constantly in- creases with decreasing indentation depth,indicating a strong size effects. In addition to the experimental work, molecular dynamics simulations of nanoindentation process have been conducted to elucidate the mechanics and mechanisms of na- noindentation of thin films. MD simulations results show that due to size effect the plastic deformation via amorphous trans- formation is more favorable than via the generation and propa- gation of dislocations in nanoindenation of single crystal cop- per thin films. Simulations results also elucidate the reason of size effects from the atomistic point of view.