Квантовый размерный эффект и осцилляции Шубникова–де Гааза в поперечном магнитном поле в полупроводниковых нитях Bi0,92Sb0,08

The transport properties, magnetoresistance, and Shubnikov–de Haas (SdH) oscillations of glass-coated Bi0.92Sb0.08 single-crystal wires with diameters of 180 nm to 2.2 mm and the (1011) orientation along the wire axis, which are prepared by liquid phase casting, have been studied. For the first time, it has been found that the energy gap DE increases by a factor of 4 with a decrease in the wire diameter d owing to the manifestation of the quantum size effect. This significant increase in the energy gap can occur under conditions of an energy–momentum linear dispersion relation, which is characteristic of both the gapless state and the surface states of a topological insulator. It has been shown that, in a strong magnetic field at low temperatures, a semiconductor–semimetal transition occurs; it is evident in the temperature dependences of resistance in a magnetic field. An analysis of the SdH oscillations, namely, the phase shift of the Landau levels and the features of the angular dependences of the oscillation periods, suggests that the combination of the manifestation of the topological insulator properties and the quantum size effect leads to the occurrence of new effects in low-dimensional structures, which requires new scientific approaches and applications in microelectronics

The influence of Fermi surface anisotropy and the charge carrier surface scattering kinetics on the electrical conductivity of a thin metal film in the view of the quantum size effect

The electrical conductivity of a thin metal film in an alternating electric field is calculated considering the quantum size effect. The Fermi surface of the metal has the shape of an ellipsoid of rotation, the main axis of which is parallel to the plane of the film. The quantum kinetic equation obtained from the von Neumann equation (the Liouville quantum equation) is solved. The Soffer model is used as the boundary conditions for the distribution function. The dependence of the electrical conductivity on the film thickness is analyzed. A comparison is made with experimental data on the electrical conductivity of bismuth thin films.

Efficient photocatalytic conversion of benzene to phenol on stabilized subnanometer WO3 quantum dots

Subnanometer WO3 quantum dots are spontaneously produced in a mesoporous silica matrix. Efficient photocatalytic conversion of benzene to phenol without decomposition of the product is realized by band engineering with a strong quantum size effect.

Поляризованная люминесценция наноточек MoS-=SUB=-2-=/SUB=-

The effect of temperature on the polarization of the luminescence of the colloidal system of MoS2 nanodots in n-methylpyrrolidone is studied under the condition of linearly polarized excitation. Nanodots are obtained by chemical exfoliation and dispersion of MoS2 microcrystals in a liquid medium under the action of ultrasound. The photoluminescence spectrum of the ensemble of MoS2 nanodots is significantly shifted towards shorter wavelengths with respect to the luminescence spectrum of bulk crystals, which is explained by the quantum-size effect in the electronic spectrum of MoS2 nanocrystals. It is shown that the temperature dependence of the anisotropy of the radiation of nanodots is described by the Levshin-Perrin equation, which takes into account the rotational diffusion of luminescent particles in the liquid matrix. The size of photoexcited nanodots in the framework of the Levshin-Perrin model turns out to be ≥ 1.5 nm and increases with increasing the emission wavelength. It is shown that the sizes of MoS2 nanodots obtained by analyzing the temperature dependence of the emission anisotropy are in satisfactory agreement with the data obtained by analyzing the quantum-size effect in the electronic spectrum of nanodots.