Reitsma Mark G, Gates Richard S, Friedman Lawrence H, Cook Robert F
Nanomechanical Properties Group, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Rev Sci Instrum. 2011 Sep;82(9):093706. doi: 10.1063/1.3624700.
Prototype cantilevers are presented that enable quantitative surface force measurements using contact-mode atomic force microscopy (AFM). The "hammerhead" cantilevers facilitate precise optical lever system calibrations for cantilever flexure and torsion, enabling quantifiable adhesion measurements and friction measurements by lateral force microscopy (LFM). Critically, a single hammerhead cantilever of known flexural stiffness and probe length dimension can be used to perform both a system calibration as well as surface force measurements in situ, which greatly increases force measurement precision and accuracy. During LFM calibration mode, a hammerhead cantilever allows an optical lever "torque sensitivity" to be generated for the quantification of LFM friction forces. Precise calibrations were performed on two different AFM instruments, in which torque sensitivity values were specified with sub-percent relative uncertainty. To examine the potential for accurate lateral force measurements using the prototype cantilevers, finite element analysis predicted measurement errors of a few percent or less, which could be reduced via refinement of calibration methodology or cantilever design. The cantilevers are compatible with commercial AFM instrumentation and can be used for other AFM techniques such as contact imaging and dynamic mode measurements.
本文展示了一种原型悬臂梁，它能够使用接触模式原子力显微镜（AFM）进行定量表面力测量。“锤头”悬臂梁有助于对悬臂梁的弯曲和扭转进行精确的光学杠杆系统校准，从而能够通过横向力显微镜（LFM）进行可量化的粘附力测量和摩擦力测量。至关重要的是，单个具有已知弯曲刚度和探针长度尺寸的锤头悬臂梁可用于原位进行系统校准以及表面力测量，这大大提高了力测量的精度和准确性。在LFM校准模式下，锤头悬臂梁允许产生光学杠杆“扭矩灵敏度”，以量化LFM摩擦力。在两台不同的AFM仪器上进行了精确校准，其中扭矩灵敏度值的相对不确定度指定为低于百分之一。为了研究使用原型悬臂梁进行精确横向力测量的潜力，有限元分析预测测量误差为百分之几或更小，这可以通过改进校准方法或悬臂梁设计来降低。这些悬臂梁与商业AFM仪器兼容，可用于其他AFM技术，如接触成像和动态模式测量。
