Stan G, Krylyuk S, Davydov A V, Vaudin M D, Bendersky L A, Cook R F
Ceramics Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.
Ultramicroscopy. 2009 Jul;109(8):929-36. doi: 10.1016/j.ultramic.2009.03.025. Epub 2009 Mar 25.
Quantitative measurements of the elastic modulus of nanosize systems and nanostructured materials are provided with great accuracy and precision by contact-resonance atomic force microscopy (CR-AFM). As an example of measuring the elastic modulus of nanosize entities, we used the CR-AFM technique to measure the out-of-plane indentation modulus of tellurium nanowires. A size-dependence of the indentation modulus was observed for the investigated tellurium nanowires with diameters in the range 20-150nm. Over this diameter range, the elastic modulus of the outer layers of the tellurium nanowires experienced significant enhancement due to a pronounced surface stiffening effect. Quantitative estimations for the elastic moduli of the outer and inner parts of tellurium nanowires of reduced diameter are made with a core-shell structure model. Besides localized elastic modulus measurements, we have also developed a unique CR-AFM imaging capability to map the elastic modulus over a micrometer-scale area. We used this CR-AFM capability to construct indentation modulus maps at the junction between two adjacent facets of a tellurium microcrystal. The clear contrast observed in the elastic moduli of the two facets indicates the different surface crystallography of these facets.
通过接触共振原子力显微镜（CR-AFM）能够高精度、高精准度地对纳米尺寸系统和纳米结构材料的弹性模量进行定量测量。作为测量纳米尺寸实体弹性模量的一个例子，我们使用CR-AFM技术测量碲纳米线的面外压痕模量。对于所研究的直径在20 - 150nm范围内的碲纳米线，观察到了压痕模量的尺寸依赖性。在这个直径范围内，由于明显的表面硬化效应，碲纳米线外层的弹性模量显著增强。采用核壳结构模型对直径减小的碲纳米线的外层和内层弹性模量进行了定量估计。除了局部弹性模量测量外，我们还开发了一种独特的CR-AFM成像能力，以在微米尺度区域绘制弹性模量图。我们利用这种CR-AFM能力在碲微晶两个相邻晶面的交界处构建压痕模量图。在两个晶面的弹性模量中观察到的清晰对比度表明了这些晶面不同的表面晶体学特征。
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