Instituto Universitario de Investigación en Óptica y Nanofísica, Campus de Espinardo, Universidad de Murcia, E-30100 Murcia, Spain.
Nanotechnology. 2013 May 10;24(18):185701. doi: 10.1088/0957-4484/24/18/185701. Epub 2013 Apr 10.
A method to precisely calibrate the oscillation amplitude in dynamic scanning force microscopy is described. It is shown that the typical electronics used to process the dynamic motion of the cantilever can be adjusted to transfer the thermal noise of the cantilever motion from its resonance frequency to a much lower frequency within the typical bandwidth of the corresponding data acquisition electronics of a scanning force microscopy system. Based on this concept, two procedures for the calibration of the oscillation amplitude are proposed. One is based on a simple calculation of the root mean square deviation measured at the outputs of the electronics used to process the dynamic motion of the cantilever, and the second one is based on analysis of the corresponding spectrum and the calculation of the quality factor, the resonance frequency and the signal strength.We show that the proposed scheme for amplitude calibration using thermal noise is experimentally and theoretically robust, with soft as well as with hard cantilevers. Moreover, it is directly related to well-defined quantities such as the force constant and thermal energy, in contrast to the calibration using amplitude versus distance curves, which requires non-trivial a priori assumptions regarding the amplitude versus distance relation.
描述了一种精确校准动态扫描力显微镜中振动幅度的方法。结果表明，可以调整用于处理悬臂梁动态运动的典型电子设备，以便将悬臂梁运动的热噪声从其共振频率转移到扫描力显微镜系统的相应数据采集电子设备的典型带宽内的低得多的频率。基于这个概念，提出了两种用于校准振动幅度的程序。一种基于对用于处理悬臂梁动态运动的电子设备的输出处测量的均方根偏差的简单计算，另一种基于对应频谱的分析和质量因数、共振频率和信号强度的计算。结果表明，使用热噪声进行幅度校准的方案在实验和理论上都是稳健的，无论是软悬臂梁还是硬悬臂梁都适用。此外，与使用幅度与距离曲线进行校准相比，该方案与诸如力常数和热能等明确定义的量直接相关，而使用幅度与距离关系进行校准需要对幅度与距离关系进行非平凡的先验假设。
