Tang B, Ngan A H W, Pethica J B
Department of Mechanical Engineering, University of Hong Kong, Pokfulam Road, Hong Kong 999077, People's Republic of China.
Nanotechnology. 2008 Dec 10;19(49):495713. doi: 10.1088/0957-4484/19/49/495713. Epub 2008 Nov 19.
A method is proposed for quantitatively measuring the elastic modulus of materials using atomic force microscopy (AFM) nanoindentation. In this method, the cantilever deformation and the tip-sample interaction during the early loading portion are treated as two springs in series, and based on Sneddon's elastic contact solution, a new cantilever-tip property α is proposed which, together with the cantilever sensitivity A, can be measured from AFM tests on two reference materials with known elastic moduli. The measured α and A values specific to the tip and machine used can then be employed to accurately measure the elastic modulus of a third sample, assuming that the tip does not get significantly plastically deformed during the calibration procedure. AFM nanoindentation tests were performed on polypropylene (PP), fused quartz and acrylic samples to verify the validity of the proposed method. The cantilever-tip property and the cantilever sensitivity measured on PP and fused quartz were 0.514 GPa and 51.99 nm nA(-1), respectively. Using these measured quantities, the elastic modulus of acrylic was measured to be 3.24 GPa, which agrees well with the value measured using conventional depth-sensing indentation in a commercial nanoindenter.
提出了一种使用原子力显微镜（AFM）纳米压痕定量测量材料弹性模量的方法。在该方法中，加载初期的悬臂梁变形和针尖-样品相互作用被视为两个串联的弹簧，并且基于斯奈登的弹性接触解，提出了一种新的悬臂梁-针尖特性α，它与悬臂梁灵敏度A一起，可以通过对两种弹性模量已知的参考材料进行AFM测试来测量。假设在校准过程中针尖不会发生明显的塑性变形，那么所测得的特定于所用针尖和仪器的α值和A值可用于精确测量第三个样品的弹性模量。对聚丙烯（PP）、熔融石英和丙烯酸样品进行了AFM纳米压痕测试，以验证所提方法的有效性。在PP和熔融石英上测得的悬臂梁-针尖特性和悬臂梁灵敏度分别为0.514 GPa和51.99 nm nA⁻¹。使用这些测量值，测得丙烯酸的弹性模量为3.24 GPa，这与在商用纳米压痕仪中使用传统深度传感压痕测得的值非常吻合。
