We present the fabrication of thick and dense carbon nanotube networks in the form of freestanding films (CNTFs) and the study of their electric resistance as a function of the temperature, from 4 to 420 K. A nonmetallic behavior with a monotonic $R\left(T\right)$ and a temperature coefficient of resistance around $-7\times {10}^{-4}{\text{K}}^{-1}$ is generally observed. A behavioral accordance of the CNTF conductance with the temperature measured by a solid-state thermistor (ZnNO, Si, or Pt) is demonstrated, suggesting the possibility of using CNTFs as temperature small-sized (freely scalable) sensors, besides being confirmed by a wide range of sensitivity, fast response, and good stability and durability. Concerning electric behavior, we also underline that a transition from nonmetal to metal slightly below 273 K has been rarely observed. A model involving regions of highly anisotropic metallic conduction separated by tunneling barrier regions can explain the nonmetallic to metallic crossover based on the competing mechanisms of the metallic resistance rise and the barrier resistance lowering.

Low-temperature magnetic force microscopy has been used to visualize spontaneous formation of vortex-antivortex pairs in hybrid ferromagnet/superconductor systems. Vortex-antivortex pairs are induced by the periodic stray field of the ferromagnet. We find general equilibrium conditions for which spontaneous vortex-antivortex pairs are formed during zero-field cooling of the hybrid ferromagnet/superconductor bilayers. Vortices can be generated by the ferromagnet domains in the absence of an external field and they are thermodynamically stable for values of the stray field and the period of the stripe magnetic domains that exceed a certain threshold.

Among all transition metal oxides, titanium dioxide (TiO₂) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO₂ thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250–1000 °C, and the TiO₂ thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO₂ thickness and annealing temperature, both ultimately affecting the degree of crystallinity.

Apolar syndiotactic polystyrene (s-PS) can easily form a stable clathrate co-crystalline phase with highly polar 4-nitroaniline molecules. The ferroelectric response of thin films containing the s-PS/4-nitroaniline clathrate phase has been investigated by scanning piezoresponse force microscopy (SPFM) and compared with the response of a poly(vinylidene-fluoride-trifluoroethylene) P(VDF-TrFE) copolymer film. Measurements show that ferroelectric polymer materials can be obtained by crystalline phases whose polarity is given by low-molecular-mass guest molecules rather than by polymer chain polarity. Moreover, as for P(VDF-TrFE), nanoimprinting processes can be applied to these materials by using the SPFM technique but, in the absence of external fields, the SPFM images are lost through an exponential intensity decay.