关于轻敲式原子力显微镜动力学系统中能量耗散的研究

STUDY ON ENERGY DISSIPATION IN THE DYNAMIC SYSTEM OF TAPPING MODE ATOMIC FORCE MICROSCOPE

原子力显微镜是一种典型的微纳谐振器,其核心部件是一个对微弱力极敏感的微悬臂梁探针,当它在不同的环境工作时,存在着各种不同形式、不同性质的能量耗散,这些能量耗散与系统的相位图像有着密切的联系.在众多的耗散机制中,只有针尖与样品的黏附接触耗散才能真正反映样品的性质,其他耗散会降低黏附接触耗散在系统总耗散中的占比,使得图像中的有效信息被削弱.因而,明确其他耗散对系统品质因数的量级贡献是十分重要的,这有助于提高图像的品质.为了研究这些耗散,本文根据耗散机理产生的原因对不同的能量耗散进行了细致的分类,系统总结了各种能量耗散的类型.之后,通过理论、实验和仿真的方法探究了在不同环境下、不同位置处微悬臂梁探针的能量耗散,明确了不同耗散对系统品质因数的量级贡献.然后,对于不同流体环境下的能量耗散,对比了它们的作用机理及量级大小.最后,对于在大气环境下工作的原子力显微镜探针,研究了它在振动过程中从高于样品表面到下降并接触样品这一连续过程中不同阶段存在的能量耗散,分析表明,在这些能量耗散中对系统品质因数影响最大的是由空气引起的耗散,包括空气黏性阻尼,压膜阻尼及液桥耗散.

Atomic force microscope is a typical micro-nano resonator and its core component is a micro-cantilever beam probe,which is extremely sensitive to weak force.When it works in different environments,there are various forms and characteristics of energy dissipation mechanisms.These energy dissipations are closely related to the phase image of the system.Among the many dissipation mechanisms,we believe that only the adhesive contact dissipation between the tip of the probe and the sample can truly reflect the nature of the sample,and the other dissipations will reduce the proportion of adhesive contact dissipation in the total dissipation of the system,thus weakening the effective information in the phase image.Therefore,it is important to clarify the quantitative contribution of other dissipations to the quality factor of the system,which helps us to improve the quality of the phase image.In order to study these dissipations,in this paper,we meticulously classify different energy dissipations according to the causes of the dissipation mechanism and systematically summarize the different types of energy dissipations.Then,we study the energy dissipation of micro-cantilever beam probe in different environments and at different positions by theoretical,experimental and simulation methods,and the magnitude contribution of different dissipation to the quality factor of the system is also clarified.Then,for the energy dissipation in different fluid environments,we compare their mechanism of action and their magnitude contribution to the quality factor of the system.Finally,for an atomic force microscope probe operating in an atmospheric environment,we investigate the energy dissipation at different stages of the vibration process from above the sample surface to descending and touching the sample,and the analysis shows that the most significant impact on the system quality factor is caused by the air,including air viscosity damping,squeeze film damping and liquid bridge dissipation.