Chan Nicholas, Lin Carrie, Jacobs Tevis, Carpick Robert W, Egberts Philip
Department of Mechanical and Manufacturing Engineering, University of Calgary, 40 Research Place NW, Calgary, Alberta T2L 1Y6, Canada.
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15621, USA.
Beilstein J Nanotechnol. 2020 May 6;11:729-739. doi: 10.3762/bjnano.11.60. eCollection 2020.
The interaction potential between two surfaces determines the adhesive and repulsive forces between them. It also determines interfacial properties, such as adhesion and friction, and is a key input into mechanics models and atomistic simulations of contacts. We have developed a novel methodology to experimentally determine interaction potential parameters, given a particular potential form, using frequency-modulated atomic force microscopy (AFM). Furthermore, this technique can be extended to the experimental verification of potential forms for any given material pair. Specifically, interaction forces are determined between an AFM tip apex and a nominally flat substrate using dynamic force spectroscopy measurements in an ultrahigh vacuum (UHV) environment. The tip geometry, which is initially unknown and potentially irregularly shaped, is determined using transmission electron microscopy (TEM) imaging. It is then used to generate theoretical interaction force-displacement relations, which are then compared to experimental results. The method is demonstrated here using a silicon AFM probe with its native oxide and a diamond sample. Assuming the 6-12 Lennard-Jones potential form, best-fit values for the work of adhesion ( ) and range of adhesion ( ) parameters were determined to be 80 ± 20 mJ/m and 0.6 ± 0.2 nm, respectively. Furthermore, the shape of the experimentally extracted force curves was shown to deviate from that calculated using the 6-12 Lennard-Jones potential, having weaker attraction at larger tip-sample separation distances and weaker repulsion at smaller tip-sample separation distances. This methodology represents the first experimental technique in which material interaction potential parameters were verified over a range of tip-sample separation distances for a tip apex of arbitrary geometry.
两个表面之间的相互作用势决定了它们之间的粘附力和排斥力。它还决定了界面性质，如粘附力和摩擦力，并且是接触力学模型和原子模拟的关键输入参数。我们已经开发出一种新颖的方法，使用调频原子力显微镜（AFM），在给定特定势函数形式的情况下，通过实验确定相互作用势参数。此外，该技术可以扩展到对任何给定材料对的势函数形式进行实验验证。具体而言，在超高真空（UHV）环境中，使用动态力谱测量法确定AFM针尖顶端与名义上平坦的基底之间的相互作用力。针尖的几何形状最初是未知的，并且可能是不规则形状，通过透射电子显微镜（TEM）成像来确定。然后用它来生成理论相互作用力-位移关系，再将其与实验结果进行比较。这里使用带有天然氧化物的硅AFM探针和金刚石样品对该方法进行了演示。假设采用6-12 Lennard-Jones势函数形式，确定的粘附功（ ）和粘附范围（ ）参数的最佳拟合值分别为80±20 mJ/m和0.6±0.2 nm。此外，实验提取的力曲线形状显示出与使用6-12 Lennard-Jones势计算的结果不同，在较大的针尖-样品分离距离处吸引力较弱，在较小的针尖-样品分离距离处排斥力较弱。这种方法代表了第一种实验技术，其中在一系列针尖-样品分离距离上，对任意几何形状的针尖顶端的材料相互作用势参数进行了验证。
