Composites made of titania (TiO2), zinc oxide (ZnO) or graphitic carbon nitride (g-C3N4) nanoparticles (20–100 nm) in polymethyl methacrylate (PMMA) were fabricated and studied. Nanodispersed powders of these semiconductors were mixed with mechanically grinded PMMA at a weight ratio ranging from 1 : 5 to 1 : 20. The mixture was dissolved in acetone and deposited onto the water surface. Upon solidification and drying in air porous discs as thick as 50–200 μm were formed. They were found to have a mechanical durability at the semiconductor to PMMA ratio above 1 : 20. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction of the samples demonstrated that semiconducting nanoparticles are quasiuniformly distributed in the polymer matrix. Their crystal structure, the particle size, and the composition of the samples do not change as compared to the started powders. Photocatalytic activity of the synthesized composites estimated by decolarization of water solution of the test dye (methylene blue) under UV irradiation was found to be reduced in the sequence TiO2, g-C3N4, ZnO.

Equivalent electrical circuits of multilayer film structures with memristor switching of resistance at interlayer boundaries and at the boundaries of crystal grains in each layer are proposed. Numerical modeling of the current-voltage characteristics of such structures has shown that their loop-shaped form, typical of memristors, is transformed into a linear ohmic dependence of the total current on the magnitude of the applied external voltage as both the number of layers and the number of grains in each layer increase. A certain combination of the number of layers and grains in a layer has been established, at which the maximum total current flowing through the structure and the ratio of resistances in the “off” and “on” states reach the highest values.

The recent results of the investigations performed in the research units of the Department of Micro- and Nanoelectronics of Belarusian State University of Informatics and Radioelectronics in the field of the development of perspective optical and electronic intra-chip and inter-chip interconnections of silicon integrated circuits are summarized. Examples of the use of nanostructured materials for the proposed light sources and detectors (Si) as well as light guides (Al2O3/TiO2) integrated with monocrystalline silicon are presented. The strategy of an application of inter-chip interposers for optical and electronic connections in bulk (2.5D and 3D) packages of integrated circuits was promoted and tested. Novel materials and structures promising for light sources, optically transparent electrical conductors and protectors against microwave electromagnetic radiation are demonstrated.

Al/g-C3N4/Si/Al, Al/g-C3N4/SiO2/Si/Al, Al/g-C3N4/Al and Al/g-C3N4/Al2O3/Al structures were fabricated by rapid chemical vapor deposition of graphitic carbon nitride (g-C3N4) from melamine onto silicon (Si) and aluminum (Al) substrates partially coated with appropriate oxide – SiO2 or Al2O3 – and Al contacts deposited on the surface. Their capacitance-voltage characteristics and frequency dependence of the capacitance were measured at room temperature. It was found that the permittivity of g-C3N4 is 14 in structures on silicon and 9–10 in structures on aluminum. The decrease in permittivity is explained by the formation of Al2O3 at the g-C3N4/Al boundary during the deposition of g-C3N4, as indicated by the results of the X-ray diffraction analysis of the formed samples.

Rapid chemical vapor deposition of continuous thin films of graphitic carbon nitride (g-CN) material with stoichiometry close to its ideal g-C3N4 form on silicon and glass substrates is demonstrated. It allows fabrication of 200-1200 nm g-CN films within 3-5 min at 500-620 degrees C instead of earlier reported few hours. SEM, XRD and EDX analysis of the films revealed their grain-layered structure and high crystallinity. The film thickness and crystallinity were found to have maximum at synthesis temperature of 575-600 degrees C. Energy band gap of the material changes with the deposition temperature too and reaches its maximum of 2.98 eV at 600 degrees C. Depen-dence of the film properties on the deposition temperature evidences competition between the rates of synthesis and evaporation of the synthesized material. The developed approach is energy budget saving and could be scaled up using conventional rapid thermal processing equipment opening a way to practical g-CN based elec-tronics and optoelectronics.

The synthesis of a composite material based on graphitic carbon nitride by pyrolytic decomposition at 550 °C of a mechanical mixture of thiourea with the addition of aluminum powder in the amount of 5–30 wt.% has been studied. According to the scanning results by means of electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry the synthesized material consists of carbon nitride, aluminum sulfide, residual metallic aluminum and aluminum hydroxide. The excess of metallic aluminum is due to the partial interaction with sulfur-containing volatile substances formed during the thermal decomposition of thiourea. It is shown that the intensity and width of the photoluminescence spectra of the synthesized composites are determined by the aluminum concentration in the initial mixture. As the aluminum concentration increases from 5 to 30 wt.%, the photoluminescence intensity maximum shifts to the long wavelength region from 534 to 560 nm. This can be used to create optoelectronic devices based on the graphitic carbon nitride.

Photocatalytically active TiO2 + CuO+Cu2O composite structures on copper foil and pre-oxidized copper grids were fabricated using a novel one-step sol-gel synthesis. The sol used included titanium tetraisopropoxide, ethylene glycol monomethyl ether, and nitric acid. Scanning electron microscopy of the composites synthesized upon calcination of the dip-in deposited sol at 400–500 °C demonstrated them to consist of a granular oxide surface layer with a thickness up to 200 nm penetrated by CuO whiskers as long as up to several micrometers. Copper oxides (CuO and Cu2O), as well as titanium dioxide (TiO2) in the anatase phase, were registered by X-ray diffraction analysis. High photocatalytic activity with respect to the test pollutant Rhodamine B in an aqueous solution under UV-activation was observed. The developed surface morphology combined with an efficient separation of photogenerated charge carriers at the TiO2/(CuO or Cu2O) heterojunctions is considered to be responsible for the observed photocatalytic activity. The proposed one-step fabrication of catalytically active materials immobilized on a substrate is promising for improving existing water and air purification systems.

Electric properties of film structures consisting of two-dimensional layers , composed by nanocrystalline grains of a semiconductor are proposed to be modeled with an equivalent scheme , in which resistors indicate electrical resistance of current channels in metallic contacts , grain material , potential barriers between grains and layers . Numerical simulation within the model has shown that there is a nonuniform current distribution over the area of the contacts . Current density at their edges can be 3–6 times higher than in the center . Local currents and their distribution in the film bulk are determined by the grain structure of the film , number of the layers , electronic properties of the barriers between grains and layers .

We have herein developed a glass-forming composition and the related sol-gel technology for bonding monocrystalline silicon wafers to produce «silicon–insulator–silicon» structures. A possibility to fabricate defect-free glass-like bonding layers at the annealing temperature decreased to 1000–1100 °C is demonstrated. The composites obtained by the sol-gel method can be used in technological processes of formation of the solid compound of silicon wafers.

Using an improved heat sink from the barrier layer, the voltage of anodic electrochemical oxidation of aluminum in sulfuric electrolytes is successfully increased from the conventional limit of about 40 to 200 V. This is done by localization of the anodized regions within the windows in the niobium thin film masks with the diameters of 0.3 μm to 2.5 mm. High‐voltage anodization in water solutions of sulfuric acid is observed to be accompanied by a reproducible formation of densely packed alumina nanotubes and intense gas propulsion from the pores of the forming alumina. The latter is proposed and experimentally confirmed for use as an efficient driving agent in micro‐ and nanoengines. Test samples are accelerated to the velocities up to 1 cm s −1 , demonstrating a thrust‐to‐weight ratio of about 1000.

Using differential thermal analysis and thermogravimetry, we have studied thermal decomposition of a mechanical mixture of thiourea and zinc acetate, resulting in the formation of a composite material consisting of graphitic carbon nitride and zinc acetate, g-C3N4/ZnS, and possibly containing zinc oxide (ZnO) inclusions. In the case of a mixture containing the stoichiometric sulfur : zinc ratio for zinc sulfide synthesis, one can obtain a material containing only ZnS semiconductor crystals embedded in a g-C3N4 matrix. ZnS is formed in the temperature range 317–367°C as a result of decomposition of zinc complexes with thiourea. Heating the mixture to above 560°C increases the rate of the thermal decomposition of g-C3N4, which reaches completion between 720 and 740°C. The presence of oxygen in the reaction atmosphere also accelerates this process, without significantly changing the temperature range of synthesis or decomposition of reaction products. The proposed technique can be used for the synthesis of g-C3N4-based composite materials and other semiconducting metal sulfides.

Graphitic carbon nitride (g-C3N4 ) was synthesized by pyrolysis of thiocarbamide and a subsequent polymerization of its products at 500 °С. After grinding the synthesized material, aqueous suspensions with the concentrations of the particles of 100–300 μg/ml were prepared from it. The antibacterial activity of the material under irradiation with the LED’s visible light for 60–120 min was confirmed for Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.

A model of charge carrier transport in heterojunction solar cells composed of a solar light‐absorbing semiconductor and a wide‐bandgap semiconducting metal oxide is proposed. It describes an electric field in the semiconductor originating from the difference in the electron work functions between the two contacting materials, an enhanced hole separation by this field, and subsequent trap‐assisted tunneling of holes through the semiconducting oxide. The model predicts a dramatic influence of the donor concentration in the semiconductor, trap parameters in the oxide, and ideality factor of the semiconductor/oxide heterojunction on the performance of the cell. The efficiency of the solar energy harvesting by MoO x /n‐Si solar cells is calculated to reach 23% of the donor concentration in Si of 10 18 cm −3 at a limited hole current density. It is predicted to be reduced to 16−18% when donor concentration is in the range of 10 15 −10 16 cm −3 . The numerical predictions agree well with experimental data, at least for donor concentrations in Si below 10 18 cm −3 , confirming suitability of the model for heterojunction solar cells composed of other semiconductors and semiconducting metal oxides.

A ternary heterosystem consisting of crystalline graphitic carbon nitride, zinc oxide, and zinc sulfide (g-C3N4/ZnO/ZnS) was obtained by the one-stage decomposition of a mixture of thiourea and zinc acetate. The integral toxicity index of the resulting material was estimated in a luminescent test with a genetically modified Escherichia coli strain as a test object. The effect of quenching the luminescence of E. coli was noted both under exposure to UV radiation due to photocatalytic reactions on the surface of g-C3N4/ZnO/ZnS leading to the formation of highly oxidative radical ions interacting with cell membranes and without irradiation due to mechanical interactions with bacterial cells. At a 0.3 g/L concentration of g-C3N4/ZnO/ZnS in aqueous solution, the toxicity index T reached 75.6% under UV irradiation. In this case, an increase in the toxicity index T of the ternary heterosystem in a test concentration range from 0.1 to 0.3 g/L was 6 or 10–11% under UV radiation or without illumination, respectively, as compared with that of the pure graphite-like carbon nitride obtained under identical conditions.

We have developed a technology and for the first time, present here, the fabrication of continuous two-dimensionally crystallized g-C3N4 layered thin films oriented in a hexagonal lattice c-plane on glass and monocrystalline silicon substrates using chemical vapor deposition from a melamine source. Scanning electron microscopy and X-ray diffraction studies revealed that such films with a smooth surface and good crystalline quality as thick as up to 1.2 mu m can be formed at a synthesis temperature of 550-625 degrees C. They are transparent in the visible range and demonstrate intense photoluminescence (PL) at room temperature. It was found that the band gap of the obtained material and its PL spectral range are shifting to the lower energies at high synthesis temperatures. Oriented g-C3N4 layered thin films deposited on flat solid substrates are promising for integrated electronics and optoelectronics.

State-of-the-art technologies of fabrication of monolayers of transition metal dichalcogenides like MeX2, where Me = Mo, W; X = S, Se, Te, and their based heterostructures are considered. Results of theoretical modeling are analyzed and possibilities of band gap engineering by means of strains, impurities, vacancies, various layer stacking and combination of different materials are presented. Vacancies and impurities in the positions of metal atoms are shown to drastically change the band gap, even leading to an appearance of metallic properties, whereas a substitution of chalcogen atoms by isovalent atoms changes the properties not so dramatically. Possible applications of heterostuctures with tunable band gaps in transistors, light-emitting diodes, photoelectrochemical cells or photovoltaic devices are proposed and their advantages in comparison with commonly used analogues are discussed. (c) 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conferences & Exhibition on Nanotechnologies, Organic Electronics & Nanomedicine - NANOTEXNOLOGY 2020.

By means of ab-initio techniques we have investigated changes in the structure and electronic properties of alkaline-earth metal silicide (Ca2Si, Mg2Si and MgCaSi) nanotubes caused by the curvature-induced effects. It is revealed that the curvature-induced effects can: 1) stabilize Mg2Si nanotubes in a phase, which is metastable for the parent 2D Mg2Si; 2) lead to an energy gain as a result of 2D to nanotube structural transformation in the case of ternary MgCaSi nanotubes; 3) modify the band dispersion and band gaps for nanotubes with the diameters less than 30 angstrom. In addition, Mg2Si and MgCaSi nanotubes are found to be direct band-gap (0.5-1.2 eV) materials with appreciable oscillator strength of the first direct transitions.

We have found one step synthesized g-C3N4/ZnO/ZnS composite to be promising for engineering of white-light sources. The composite was fabricated by simultaneous pyrolytic decomposition of thiourea and zinc acetate with a consequent in situ polymerization of the products at 550-625 degrees C and characterized by SEM, XRD, EDX and low temperature PL spectroscopy. The composite synthesized at 550 degrees C demonstrates blue PL with a peak at 2.74 eV while higher temperatures of the synthesis result in a broad spectra with a maximum at 2.22 eV and comprise of the bands of g-C3N4 and mixed ZnO/ZnS as they have been resolved by low temperature PL. The proper selection of the synthesis temperature allows an extension of light emitting spectra of g-C3N4/ZnO/ZnS composites from blue to white light range. The results obtained show ternary systems containing g-C3N4 and wide band-gap semiconductors are suitable for white-light emitting and optoelectronic devices.

The possibilities and conditions for modifying the band gap and the behavior of interband transitions under compressive and tensile strains in the crystal lattice of a molybdenum disulfide monolayer have been determined by theoretical modeling. It is shown that depending on the value and direction of the strains the compound may be a direct-gap or indirect-gap semiconductor, and the conditions for such transformations are determined. The results demonstrate a potential use of the molybdenum disulfide monolayer in nanoelectronic devices of new generation in which controlled transport of charge carriers is possible