Long-distance fiber-optic quantum key distribution using superconducting detectors

This paper presents the results of experimental studies on quantum key distribution in optical fiber using superconducting detectors. Key generation was obtained on an experimental setup based on a self-compensation optical circuit with an optical fiber length of 101.1 km. It was first shown that photon polarization encoding can be used for quantum key distribution in optical fiber over a distance in excess of 300 km.     

Modeling the formation of silicon nanoclusters during annealing SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> layers

The mechanism of formation of silicon nanoclusters in layers of nonstoichiometric composition is studied by Monte Carlo simulation. Interest in silicon nanoclusters (Si-nc) coated with an oxide layer is due to their applications in modern optoelectronics and nanoelectronics. A lattice Monte Carlo model is proposed to study atomic processes in the Si-SiO₂ system. The formation of silicon nanoclusters during annealing of single SiO layers and SiO₂-SiO-SiO₂ layered structures is studied. Along with the diffusive motion of particles, the model takes into account the formation and collapse of mobile molecules of silicon monoxide. It is shown that accounting for transport of silicon under high-temperature annealing due to the motion of SiO accelerates the formation of Si-nc. Dependences of the size of nanoclusters on temperature, annealing time, and the composition of the SiO _x layer are obtained. It is found that annealing of silica films containing layers of nonstoichiometric composition can lead to the formation of silicon nanoclusters or cavities.     

Radiation detectors based on PbSnTe:In films,sensitive in the terahertz range of the spectrum

This paper presents a review of studies of the photoelectric properties of PbSnTe:In films obtained by molecular beam epitaxy and photosensitive structures in the far infrared and submillimeter ranges based on these films. The parameters of photodetector arrays of this type and detectors based on doped semiconductors and superconductors are compared. One-dimensional (2×128 elements) and two-dimensional (128 × 128 elements) PbSnTe:In based arrays with a sensitivity threshold of ~22 μm and an operating temperature of T ≤ 16 K are implemented. Under background-free conditions, the noise equivalent power (NEP) was NEP ≤ ^10?18 W/Hz^0.5 at T = 7 K for a black body radiation source at T_BB = 77 K. In the submillimeter range of the spectrum, sensitivity to laser radiation with a wavelength λ ≤ 205 μm and a value NEP ≤ 10^?12 W/Hz^0.5 was observed without optimization of the design of the photosensitive element and minimization of the measurement circuit noise. The directions of the development of PbSnTe:In based radiation detectors are considered..     

Oscillating transient currents in PbSnTe:In in a backgroundless mode

Damping oscillations of a current are found in the PbSTe:In films after supplying a direct voltage to them in the absence of background illumination. A nonmonotonic transition to the steady state is discussed in the scope of the theory of the currents confined by a space charge upon the capture of electrons injected from the contacts to the traps distributed by energy, which leads to oscillating variation in polarizability and injection current. The ratio of the total current under the excitation by laser radiation with wavelength λ = 205 μm (hν = 0.006 eV) to the dark current could be larger or smaller than unity depending on the injection level of the electrons, i.e., supplied voltage, which can be interpreted in the scope of the suggested model.     

Features of the Current Flow in Injection Structures Based on PbSnTe:In Films

This paper reports a study of the current–voltage (I–V) features of the p-i-p structures based on Pb_1–xSn_xTe:In films with the tin content х ≈ 0.31 in which the metal–insulator transition occurs. It is shown that the photocurrent is the hole current under light interband excitation, and electron trapping is dominant. The experimental and theoretical data are compared.     

The influence of the sizes of the cross section of mesapiezoresistors on their characteristics

The influence of the width of polysilicon mesapiezoresistors with dielectric insulation on their sheet resistance and piezosensitivity under the conditions of the formation of the passivation coating consisting of thermal silicon dioxide is investigated experimentally. A strong increase in the sheet resistance upon decreasing the width of mesapiezoresistors is found in the range 3 μm ≤ W ≤ 10 μm, which is associated with a decrease in the cross section and impurity segregation in the course of oxidation. The same effect is also observed for mesapiezoresistors fabricated based on SOI structures with a single-crystal silicon layer. It is established that a decrease in the width leads to an increase in the longitudinal piezosensitivity and a drop of the transverse piezosensitivity. The temperature coefficient of resistivity for the narrower boron-doped resistors weakly decreases for the selected concentration and remains constant for phosphorus-doped resistors. A simple model is suggested to interpret the behavior of the sheet resistance and piezosensitivity.     

The use of stressed silicon in MOS transistors and CMOS structures

In the review, the changes in electronic processes in the channel of the MOS transistor taking place under applying mechanical stresses are described. It is shown that the use of the stressed films of silicon nitride, the source and sink from the germanium-silicon alloy, etc., leads to an increase in the mobility of holes and electrons and to an increase in the efficiency of transistor operation. The application of this method to CMOS structures is also described.