On-demand modulation of material properties at the nanoscale is the foundation of developing various functional micro- and nanodevices, and it attracts tremendous research interests. As prototypical strongly correlated materials, vanadium dioxide (VO2) becomes a promising candidate for fabricating high-performance optoelectronic devices owing to its specific metal–insulator transition. Here, we modulate the structural and electric properties of VO2 films by using a locally confined atomic force microscope (AFM) tip-induced electric field and explore the critical roles of several key parameters including bias voltage, bias polarity, dwell time, and bias sequence. Written patterns processed with a series of setting parameters are characterized via AFM and Kelvin probe force microscopy imaging, by which the resulting changes in height and surface contact potential are quantitatively measured. Time stability and reversibility of the modulation are especially concerned. At last, potential applications in developing optoelectronic devices with arbitrary shapes are demonstrated. Our investigations are aimed to provide detailed insight into the nanomodulation of VO2 thin films by a tip-induced electric field and elucidate the possibility of writing reversible functional devices directly with an ultrahigh spatial resolution.

Measurement of interfacial properties between thin films and elastomers is investigated. As a prototype, the interface adhesion between a graphite nanoflake and an elastic polymer is determined by topography imaging of the induced graphite buckles using atomic force microscopy. A theoretical analysis is carried out to establish the relationship among interface adhesion, elastic strain energy, and buckle surface area. The strain energy of the graphite is obtained by employing an elastic plate deflection theory. To introduce the buckles, different methods are applied, including thermal contraction, bending, and stretching, and different substrate materials, namely, polydimethylsiloxane and polystyrene, are used. The uncertainty in measuring the interface adhesion is discussed. These investigations provide a promising approach to characterize the interfacial properties of multilayer samples.

Magnetic force microscopy (MFM) has become one of the most important instruments for characterizing magnetic materials with nanoscale spatial resolution. When analyzing magnetic particles by MFM, calibration of the magnetic tips using reference magnetic nanoparticles is a prerequisite due to similar orientation and dimension of the yielded magnetic fields. However, in such a calibration process, errors caused by extra electrostatic interactions will significantly affect the output results. In this work, we evaluate the magnetic moment and dipole radius of the MFM tip on Fe3O4 nanoparticles by considering the associated electrostatic force. The coupling of electrostatic contribution on the measured MFM phase is eliminated by combining MFM and Kelvin probe force microscopy together with theoretical modeling. Numerical simulations and experiments on nickel nanoparticles demonstrate the effectiveness of decoupling. Results show that the calibrated MFM tip can enable a more accurate analysis of micro-and-nano magnetism. In addition, a fast and easy calibration method by using bimodal MFM is discussed, in which the acquisition of multiple phase shifts at different lift heights is not required.

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Vanadium dioxide (VO 2 ) is widely employed in developing tunable optoelectronic devices due to its significant changes in optical and electric properties upon phase transition. To fabricate the VO 2 -based functional devices down to the micro/ nanoscale, a high-resolution processing technique is in demand. Scanning probe lithography (SPL) on the basis of a tip-induced electric field provides a promising approach for prototyping. Here, we demonstrated a precise VO 2 etching strategy by direct writing on a VO 2 film with a negative tip bias and subsequent sonication removal of the written area. The effects of bias voltage, sonication, and thermal treatment as well as the mechanical difference between the tip-modulated area and the pristine VO 2 film were investigated systematically. The results show that VO 2 can be etched layer by layer via alternately repeating tip modulation and sonication, and arbitrary patterns can be written. Based on this route, we designed a kind of metasurface by arranging VO 2 −gold nanoblocks with different sizes and heights for spectrally selective tunable reflectivity in near-and mid-infrared. This electric-field SPL method demonstrates the prominent advantages of high resolution down to several tens of nanometers, quasi-3D patterning, and resist-free maskless direct writing, which should be applicable for prototyping other micro/nanodevices.