铱单晶的纳米压痕尺寸效应研究

Nanoindentation Size Effect of Iridium Single Crystal

采用纳米压痕技术和原子力显微镜对铱（Ir）单晶（100）和（110）取向的载荷-位移曲线、弹性模量、压痕形貌、压痕硬度-加载深度等进行了研究.结果表明,Ir（100）与Ir（110）单晶的弹性模量分别为477 和493 GPa;加载深度为10~2500 nm 时,Ir 单晶的纳米压痕硬度存在压痕尺寸效应,在10~500nm 时表现更为强烈,表明随着加载深度的增加,单晶材料的硬度减小;基于Nix-Gao 模型,计算出Ir（100）和Ir（110）单晶的纳米硬度H0 分别为2.32 和2.46 GPa,当加载深度分别大于4910 和5220 nm时,Ir 单晶的纳米硬度不存在尺寸效应,可作为金属铱硬度测试的重要依据;采用硬度和深度的幂律关系计算出Ir（100）和Ir（110）单晶的尺寸效应因子（m）分别为0.44 和0.48,该值远远大于其他金属和半导体材料,这种反常现象可能与铱原子间的异常强的交互作用有关.

Load-depth curves, elastic modulus, indentation morphology as well as the relationship betweennanohardness and indent depth of （110） and （100） oriented iridium single crystals were investigated viananoindentation technique and atomic force microscopy （AFM）. The results indicate that the elasticmodulus of Ir（100） and Ir（110） is 477 GPa and 493 GPa, respectively. The indentation size effect （ISE） isobserved over the entire range of indentation depths 10~2500 nm, particularly for the depth in the range of10~500 nm. Based on Nix-Gao model, the calculated nanohardness （H0） of Ir（100） and Ir（110） is 2.32 and2.46 GPa, respectively, which is defined as the ISE disappeared. There is no ISE can be observed on Ir（100）and Ir（110） as the penetrating depth more than about 4910 and 5220 nm, respectively. By means of powerlaw, the ISE factor （m） of Ir（110） and Ir（100） are calculated as 0.48 and 0.44, respectively, which are muchgreater than those of other metallic and semi-metallic materials. This anomaly may be associated withabnormally strong interactions between atoms of iridium.