A new resonance-tracking (RT) method using fast frequency sweeping excitation was developed for quantitative scanning probe microscopy (SPM) imaging. This method allows quantitative imaging of elastic properties and ferroelectrical domains with nanoscale resolution at high data acquisition rates. It consists of a commercial AFM system combined with a high-frequency lock-in amplifier, a programmed function generator and a fast data acquisition card. The resonance-tracking method was applied to the atomic force acoustic microscopy (AFAM) and to the piezoresponse force microscopy (PFM) modes. Plots of amplitude versus time and phase versus time for resonant spectra working with different sweeping frequencies were obtained to evaluate the response speed of the lock-in amplifier. It was proved that this resonance-tracking method allows suitable spectral acquisition at a rate of about 5 ms/pixel, which is useful for SPM imaging in a practical scanning time. In order to demonstrate the system performance, images of RT-AFAM for TiN films and RT-PFM for GeTe are shown.
A study of titanium nitride (TiN) films microstructural and mechanical properties at nanoscale using resonance tracking acoustic force atomic microscopy is presented. Also for this study, the work function (Φ e ) measured for Kelvin Probe Force Microscopy of TiN films deposited by pulsed dc magnetron sputtering is analysed. The films were deposited on Si and glass substrates using a gas mixture ratio Ar-N 2 10 and 12% of N 2 and power density from 7.4 to 10.8 W cm −2 using the Pulsed DC Magnetron Sputtering. Mechanical properties at nanoscale are measured and a relation between microstructure and nanoscale elastic domains is seen. It was found that the hardness increases when the Φ e increases. This directly proportional relationship between hardness and work function, for the first time observed and reported in this contribution, is more accurate and shows a stronger dependence than the relation between hardness and microstructural properties independently.
Local characterizations of electric, magnetic, mechanical, electrochemical, and structural properties of materials by scanning probe microscopy (SPM) can be carried out by sensing variations of the contact cantilever's resonance frequencies, resulting in diverse microscopy techniques such as piezoresponse force microscopy (PFM), atomic force acoustic microscopy (AFAM) and piezomagnetic force microscopy (PmFM), to name a few. In this work, we provide a simple setup to determine such frequencies, together with the dynamic response of the SPM cantilever and its harmonics. The setup is less expensive when compared to the commercial versions and allows a better control of the in-and-out PFM. It is based on the use of the internal AC source of a lock-in amplifier controlled by software developed in LabVIEW. In order to illustrate the utility of the contact resonance frequencies in the SPM, resonance-PFM, PFM non-linearities, discrimination of ferroelectric from non-ferroelectric responses and PmFM measurements, and determination of the modulus of elasticity by AFAM are conducted. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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