Characteristics and Functionality of Cantilevers and Scanners in Atomic Force Microscopy

Horizontal Distortion Correction of AFM Images Based on Automatic Labeling of Feature Graphics

The atomic force microscope (AFM) image will be inclined and bent due to the tilt angle between the probe and the sample surface. When the least squares fitting method is used to correct the horizontal distortion of the AFM image, the shape structure that is lower or higher than the sample base will affect the final fitting correction result. In view of the limitations of existing methods and the diversity of AFM images, an AFM image level distortion correction method based on automatic feature marking is proposed. The Canny edge detection algorithm with adaptive threshold is used to automatically detect and recognize the feature graphics, and the feature graphics are zeroed by the hole filling algorithm to automatically remove the feature graphics data from the line fitting data. After completing the least squares fitting correction of all the rows of data, the full AFM image data with eliminating horizontal distortion can be obtained. Finally, the corrected full image data are used for imaging. This method can be adapted to different types of AFM images and realize automatic fitting correction of the whole image, which improves the accuracy and efficiency of correction.

Calibration of the lateral spring constant for a custom T-shaped atomic force microscopy probe

Atomic force microscopy (AFM) is a versatile tool for investigating nanotribology, where the probe's lateral spring constant is a critical parameter. This work introduced a method to calibrate the lateral spring constant of a T-shaped probe integrated into a custom AFM system. An expression for the lateral spring constant of the probe was derived by correlating the probe's lateral bending and torsional resonance frequencies with its reduced masses and moments of inertia. In the experiment, electrochemical etching was utilized to gradually reduce the mass of the probe tip. The probe's resonance was excited using three piezoelectric techniques, allowing the measurement of resonance frequencies across different vibration modes. Finite element analysis was performed to predict the lateral spring constants of probes with varying dimensions, confirming the reliability of the proposed method.

Scanning Probe Microscopies for Characterizations of 2D Materials

2D materials are intriguing due to their remarkably thin and flat structure. This unique configuration allows the majority of their constituent atoms to be accessible on the surface, facilitating easier electron tunneling while generating weak surface forces. To decipher the subtle signals inherent in these materials, the application of techniques that offer atomic resolution (horizontal) and sub-Angstrom (z-height vertical) sensitivity is crucial. Scanning probe microscopy (SPM) emerges as the quintessential tool in this regard, owing to its atomic-level spatial precision, ability to detect unitary charges, responsiveness to pico-newton-scale forces, and capability to discern pico-ampere currents. Furthermore, the versatility of SPM to operate under varying environmental conditions, such as different temperatures and in the presence of various gases or liquids, opens up the possibility of studying the stability and reactivity of 2D materials in situ. The characteristic flatness, surface accessibility, ultra-thinness, and weak signal strengths of 2D materials align perfectly with the capabilities of SPM technologies, enabling researchers to uncover the nuanced behaviors and properties of these advanced materials at the nanoscale and even the atomic scale.

Atomic Force Microscopy Applied to the Study of Tauopathies

Atomic force microscopy (AFM) is a scanning probe microscopy technique which has a physical principle, the measurement of interatomic forces between a very thin tip and the surface of a sample, allowing the obtaining of quantitative data at the nanoscale, contributing to the surface study and mechanical characterization. Due to its great versatility, AFM has been used to investigate the structural and nanomechanical properties of several inorganic and biological materials, including neurons affected by tauopathies. Tauopathies are neurodegenerative diseases featured by aggregation of phosphorylated tau protein inside neurons, leading to functional loss and progressive neurotoxicity. In the broad universe of neurodegenerative diseases, tauopathies comprise the most prevalent, with Alzheimer's disease as its main representative. This review highlights the use of AFM as a suitable research technique for the study of cellular damages in tauopathies, even in early stages, allowing elucidation of pathogenic mechanisms of these diseases.