Study on Multi-Frequency Method for Electrostatic Force Microscopy in Air

Heterodyne High-Harmonic Electrostatic Force Microscopy with Improved Spatial Resolution for Nanoscale Identification of Metallic/Semiconducting Carbon Nanotubes

“…Conventional HH-EFMs based on dual-pass or multifrequency method were developed 20 years ago, including second-order ,,, and third-order , high-harmonic modes (namely, HH-EFM-2ω and HH-EFM-3ω). They were named by dielectric force microscopy , and scanning capacitance force microscopy , according to their imaging principles in previous reports, respectively.…”

“…For example, imaging of metallic/semiconducting CNTs using dielectric force microscopy, namely second-order high-harmonic electrostatic force microscopy (HH-EFM-2ω), has been demonstrated in previous reports. − However, like other AFM technologies based on long-range interactions, the spatial resolution of electrostatic force microscopy (EFM) imaging is limited to approximately the 100 nm scale according to the configuration of the conventional dual-pass scan (lift mode). − As the electrostatic force is sensitive to the tip–sample distance, to avoid the tip scraping the sample during the second scan, a tip–sample gap is maintained, leading to the deterioration of spatial resolution. The multifrequency method based on single-pass scan provides an effective approach to optimizing the equivalent tip–sample distance, − but the signal crosstalk from electromechanical coupling sometimes cannot be eliminated completely, − and the spatial resolution is still not satisfactory enough, as it is still not superior to the tip diameter scale. Therefore, the development of new nanoscale characterization technologies for identifying metallic/semiconducting CNTs is still necessary and highly desirable.…”

Advanced atomic force microscopies and their applications in two-dimensional materials: a review

“…Interlayer coupling [7] and local variations of the elastic modulus [7,20] CR mode Contact resonance frequency and quality factor Contact stiffness and viscous response detection [21] C-AFM Current Local conductivity [22][23][24][25]] SKPM/KPFM Electric potential Surface potential (SP) [26], work function [27], contact potential difference [28], charge transfer [29,30], surface point defect/adsorbate [31][32][33], voltage drop [34], and capacitance coefficients [35], EFM Electrostatic forces Capacitance coefficients [35], SP [36], and dielectric response [37] MH-EFM Electrostatic forces SP [38], work function [39], and mobile charge carriers (MCC) [40] sMIM Microwave reflection Dielectric constant [41,42], conductivity and permittivity variation [43,44], charge carrier variations [45], and doping concentration [46] PFM Electromechanical coupling Electromechanical response [47,48], piezoelectric properties [49], and ferroelectric coercive field or lateral force microscopy (LFM) technique in that the scanning direction is perpendicular to the cantilever axis in the FFM/LFM technique [68].…”