Bi2Se3 thin films are imaged in the near-field using spectroscopic scattering type near-field optical microscopy (s-SNOM) at mid infrared laser wavelength region (9-11μm). Single phases Bi2Se3 thin film structures were prepared by mechanical exfoliation on silicon wafers. We report size and wavelength dependent near-field interaction contrasts in both optical amplitude and phase. We show that near-field optical imaging allows material specific identification and characterization of Bi2Se3 exfoliated samples including the confirmation of residual tape presence or removal in stacked films. We describe an alternative “shear exfoliation” sample preparation method which reliably deposits Bi2Se3 without the possibility of adhesive contaminants.

Peak Force Atomic Force Microscope is a new technique to characterize fragile materials such as nanoparticles with high accuracy with only one measurement. Unlike the tapping mode AFM, Peak Force AFM operates at a frequency below the resonant frequency of the cantilever. This allows for a direct control of the forces and avoids lateral forces that may damage the sample as in contact mode AFM. Furthermore, the performance characteristics of Peak Force AFM are suitable to work also in Tunneling AFM (TUNA) mode, enabling the study of the electrical properties of materials.

In this work SnS nanoparticles capped with tri-n-octylphosphine oxide (TOPO) have been characterized. By means of Peak Force AFM it is possible to measure simultaneously topography and current maps of nanoparticles, yielding information about the shape, size and the conductivity of even a single nanoparticle. The topography map clearly showed single nanoparticles with a size less than 5 nm and spherical shape. In the conductivity map it is possible to discern the same nanoparticles, the correlation with the topography map is evident. This confirms the conduction (though not calibrated) of SnS nanoparticles. This type of measurements has been repeated many times in order to check the reproducibility of this technique. Moreover, the same nanoparticles have been measured also by Torsional Resonant TUNA AFM in order to compare it with Peak Force AFM. By means of TR-TUNA it was possible to measure the topography of SnS nanoparticles capped with TOPO but not the current. Besides, the resolution of the topography map acquired by TR-TUNA AFM is inferior to Peak Force AFM. From this comparison it has been found that the conductivity of nanoparticles, even if they are capped with TOPO, can be measured by Peak Force AFM, a result that thus far has been difficult to achieve by other types of AFM.

The effect of Hf on the permanent magnetism of nanocrystalline Zr18-xHfxCo82 ribbons (x = 0, 2, 4, and 6) was investigated by magnetic properties measurement and magnetic force microscopy (MFM). Emphasis is on the local magnetic domain structures in polycrystalline rapidly solidified Zr18-xHfxCo82 ribbons for four different samples with small fractions of Hf dopants (x ≤ 6). The investigation of the magnetic properties of the Zr18-xHfxCo82 ribbons revealed that all the samples under investigation are ferromagnetic at room temperature, and the corresponding MFM images show bright and dark contrast patterns with up-down magnetic domain structures. It is found that the saturation magnetization and the coercivity depend on Hf doping concentration x in the samples. For a sample with Hf concentration x = 4, the maximum energy product (BH)max value is 3.7 MGOe. The short magnetic correlation length of 131 nm and smallest root-mean-square phase shift value of 0.680 were observed for x = 4, which suggests the refinement of the magnetic domain structure due to weak intergranular exchange coupling in this sample. The above results indicate that suitable Hf addition is helpful for the magnetic domain structure refinement, the coecivity enhancement, and the energy-product improvement of this class of rare-earth-free nanocrystalline permanent-magnet materials.

Atomic force microscopy (AFM) and Raman spectroscopy were used to characterize the morphology and the local mechanical properties of polypropylene-based graphene nanocomposites. Amplitude Modulated AFM was used to perform phase angle measurements to estimate the loss tangent, along with the local elastic modulus of the nanocomposite’s surface as a function of graphene content. We have observed an increasing trend in phase angle as the graphene content increased. We also identified wrinkled graphene flakes embedded in the polymer matrix. The graphene corrugation and mismatched strain between polymer and graphene sheets show a variation in the phase angle that is corroborated with Raman measurements. Mechanically exfoliated graphene on SiO2 was characterized as a baseline to understand the effect of graphene wrinkles compared to graphene surfaces on phase angle. The Raman results revealed that there are changes in the crystalline morphology of the polymer with the addition of graphene.

Bimodal Atomic Force Microscopy (AFM) is a recently developed dynamic AFM technique. Recent work [1] has shown the existence of different regimes of operation in Bimodal AFM depending on the operating conditions. The current work focuses on the effects of different operating parameters while imaging an impact copolymer blend of polypropylene (PP) and ethylene-propylene (E-P) rubber. The higher mode amplitude and phase contrasts reverse at different points between the PP and rubber regions as the free amplitude of the higher eigenmode is increased. The observed contrast reversal suggests that the cantilever kinetic energy and its free air drive input energy play a role in determining the regimes of operation. Understanding the role of cantilever dynamics in determining these operation regimes will help guide a more rational operation of Bimodal AFM.

Scanning Thermal Microscopy measurements with a resistive microprobe electrically heated were performed for different probe temperatures, for probe free in air and in contact with various specimens. The measured relative difference of Joule power dissipated in the probe when tip is in contact with a sample and when it is free in air is studied for different magnitude of the electrical current that heats the probe. A variation of this signal, never outlined before, is observed. A predictive modeling is used to explain these results and identify from the experimental data the global thermal conductance of the probe-sample thermal exchange for experiments performed in ambient conditions.