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Single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs) and vapor-grown carbon nanofibers (VGCNFs)/epoxy matrix nanocomposites were prepared, respectively. The microstructure of the nanocomposites was observed by SEM and the resistivities of the nanocomposites with different concentration of CNTs/VGCNFs were measured. Based on the experimental results, the dispersion of SWNTs and MWNTs were relatively poor but that of VGCNFs is uniform within the matrix. The resistivitiy of pure epoxy is about 10^10.5Ω · cm and several orders of magnitude higher than those of SWNT, MWNT and VGCNF/epoxy nanocomposites. The resistivities of the nanocomposites drop with the increase of the CNTs/VGCNFs content in the matrix and the resistivity of VGCNFs/epoxy nanocomposites was much lower than that of CNT/epoxy nanocomposites.

Hydrogenated carbon nitride films have been synthesized on Si (100) by DC reactive sputtering with RF bias. These films are characterized by transmission electron microscopy and atomic force microscopy. Hydrogenated carbon nitride films have low surface roughness. At low hydrogen fraction, the films include small crystallites. High hydrogen fraction promotes the films to be amorphous. The resistivities of the films are measured, which range from 6.35×10⁵ to 1.16×10⁸ Ω·cm. The measured resistivity results indicate that the hydrogenated carbon nitride films have semiconductive properties. The resistivity largely depends on the bonding configurations. Effects of H₂ fraction, target current and substrate bias are investigated. All these deposition parameters have influence on the resistivities. High C—H, N—H and C—NH bond fractions result in high resistivity.

We report here our investigations on dark DC resistivity and optical absorption of chemical bath deposited CdS thin films prepared by chemical bath deposition. Crystallite sizes of about 30 nm are found from XRD using Scherrer formula with an added term for strain broadening. Energy-dispersive X-ray measurement shows correct stoichiometry of Cd and S atomic ratio. The grain size of the as-deposited film determined from both AFM and TEM is found to be ~180 nm. On vacuum annealing, the dark resistivity decreases from ~10⁹ to 10⁶ Ω-cm. Dark resistivity variation of as-deposited and vacuum-annealed films with temperature in the temperature region (95–350 K) reveals that each film exhibits two types of conduction in this temperature region. From the optical absorption study the optical band gap of as-deposited film is found to be ~2.29 eV.

The electrical resistivity ρ(T) of La_0.8C_0.2MnO₃ manganite nanoparticles (particle size 18 nm and 70 nm) significantly depends on temperature and size of nanoparticles. ρ(T) of 70 nm La_0.8C_0.2MnO₃ manganite exhibits metallic phase in low temperature regime (T < 250 K), develops a maxima near 250 K and decrease with T at high temperatures (250 K < T < 300 K). However, the ρ(T) of 18 nm La_0.8C_0.2MnO₃ manganite shows insulating phase in overall temperature regime, where resistivity decrease with temperature. The resistivity in metallic phase is theoretically analyzed by considering the strong spin fluctuations effect which is modelled using Drude–Lorentz type function. In addition to the spin fluctuation-induced contribution the electron-phonon and electron-electron ρ_e-e(T) = BT² contributions are also incorporated for complete understanding of experimental data. The contributions to the resistivity by inherent acoustic phonons (ρ_ac) as well as high frequency optical phonons (ρ_op) were estimated using Bloch–Gruneisen [BG] model of resistivity. It is observed that the resistivity contribution due to electron-electron interaction shows typical quadratic temperature dependence. Resistivity in Semiconducting/insulating phase is discussed with small polaron conduction (SPC) model. Finally the theoretically calculated resistivity compared with experimental data which found consistent in wide range of temperature.

Nanoparticle dilute magnetic semiconductors (DMS) are becoming increasingly important due to their possible applications in spintronics, an emerging field where the conduction process in the materials is a spin-based process. Nanoparticles of Mn-doped ZnO (DMS) material with general formula Zn${}_{1-x}$Mn_xO ($x=0.05,0.15,0.2$) were prepared by opting single stage combustion synthesis process. The samples characterized, exhibited formation of monophasic nanoparticles of the sample with average particle size ranging between 17 nm to 23 nm. The calculations of energy bandgap made from UV absorption spectra showed variation of the bandgap from 2.18 eV to 2.32 eV. The magnetic measurements (VSM) made on the samples confirmed formation of a single diamagnetic (Zn${}_{0.95}$Mn${}_{0.05}\mathrm{\text{O}}$) and two namely (Zn${}_{0.85}$Mn${}_{0.15}\mathrm{\text{O}}$) (Zn${}_{0.8}$Mn${}_{0.2}\text{O}$) paramagnetic samples. It is interesting to see that all the three magnetic profiles exhibit hysteresis type behavior both in diamagnetic form and paramagnetic form. The resistivity of the samples was of the order of 10${}^{10}$ Ohm-cm ($\mathrm{\Omega }$-cm) at lower temperatures. Temperature-dependent resistivity curves exhibited peaking behavior for all the three samples which is very interesting. Temperature-dependent thermo-power profiles give an indication of $n$-type semiconductor behavior with significantly deep and broad minima around 100${}^{\circ }\mathrm{\text{C}}$ which becomes sharper for sample with higher Mn concentration.

One of the important phenomena influencing the resistivity behavior of nanotubes based on the change of their radius is a physical effect called “pinch effect”. In this paper, according to the experimental results, the electrical resistivity behavior of carbon nanotubes is modeled as a function of the radius in the radius range of 3–10nm. The pinch effect is not observed for weak current, but if the radius of carbon nanotube is very small, this effect will be considerable and affects carbon nanotube resistivity. The deviations observed in $\rho$–$R$ (resistivity as a function of nanotube radius) diagrams for individual carbon nanotube are justified with different parameters such as pinch effect phenomenon. The results show an acceptable theoretical model for the behavior of electrical resistivity relative to radius reduction. The theory diagram of the electrical resistivity behavior of carbon nanotubes in terms of radius reduction is predicted in very small radii. These results are consistent with the experimental results. It is consistent and generalizable.