Enhancement of contact resonance atomic force microscopy subsurface imaging by mass-attached cantilevers

Abstract

Improvement of contact resonance atomic force microscopy (CR-AFM) frequency sensitivity at a high contact stiffness condition and subsequent enhancement of its subsurface imaging capability were demonstrated by adding an additional mass on the cantilever backside near the free end. The influence of mass and its position on the CR-AFM performances was analytically investigated by using a simplified cantilever vibration model and further compared with finite element analysis. Theoretical results and FEA simulations showed good agreement and they could provide a general guide on the cantilever’s modification by attaching a proper mass to improve the CR-AFM capability. As a prototype, a Pt micro-disc with precisely controlled size and position on the cantilever, which served as the attached mass, was deposited by utilizing focused ion beam. The improvement of frequency sensitivity was verified through CR spectroscopy and subsurface imaging on cavities having pre-determined diameters and covered with highly oriented pyrolytic graphite flakes. Compared with the original unmodified cantilever, obvious enhancement of CR-AFM subsurface nano-imaging was obtained. The mass-attached cantilever can benefit characterizing sample’s mechanical properties and enhancing subsurface imaging based on tip-generated stress.

Fabrication of a VO2-Based Tunable Metasurface by Electric-Field Scanning Probe Lithography with Precise Depth Control

“…For a simple analysis, the Hertz model was used to describe the tip–sample contact mechanics, and the Euler–Bernoulli cantilever model was applied to analyze the cantilever vibration with proper boundary conditions. Details of the modeling could be found in the literature. − The geometric parameters of the probe used in calculations, such as the cantilever length, width, thickness, tip height, and tilt angle, were nominal data provided by the manufacturer. Other parameters including the cantilever stiffness, resonance frequency, and Q factor were measured experimentally.…”

“…Then, by modeling the contact mechanics as well as the cantilever vibration, the local mechanical properties of the sample, such as the contact stiffness, damping, and elastic modulus, can be evaluated. 40,41 In CR-AFM imaging, the cantilever vibration is fixed at or near the contact resonance frequency. The record amplitude image will show noticeable contrast when the local mechanical properties change.…”

Linearizing the frequency‐stiffness relation in contact resonance atomic force microscopy for facilitated mechanical characterization

“…To verify the target linear frequency-stiffness relation, we carry out CR-AFM experiments on the HOPG covered cavity. The normal contact stiffness k N can be a connection of the deflection stiffness of plate structure k S and the material deformation stiffness k M (Wang, Zhang, & Chen, 2020),…”

Subsurface phase imaging of tapping‐mode atomic force microscopy at phase resonance

“…The vibration of AFM probe is a compound vibration system composed of the fixed probe frame, the probe and the stage of piezoelectric displacement ceramic, 28,29 so the vibration of the probe is not an ideal simple probe vibration. In Figure 2A, in the amplitude spectrum curve of probe vibration, there are some non‐main resonances on both sides of the first‐order main resonance.…”