Влияние ионов неодима (III) на фотолюминесценцию сульфидов кадмия и цинка в полиакрилатной матрице

Nanoscale particles ZnS:Nd3+, CdS:Nd3+ and (Zn,Cd)S:Nd3+ were synthesized and doped in a polymerizing methyl methacrylate medium during the production of optically transparent polyacrylate composites of the composition PMMA/ZnS:Nd3+, PMMA/CdS:Nd3+ and PMMA/(Zn,Cd)S:Nd3+. The excitation of photoluminescence (FL) and FL of semiconductor structures in composites is associated with the transition of electrons from the valence band to the conduction band and to the levels of structural defects of semiconductor particles, followed by recombination at these levels. Based on changes in the excitation spectra of FL and FL composites, assumptions are made about the structure of particles, the distribution of Nd3+ ions in it and their effect on photoluminescence.

Optically Controlled Supercapacitors: Functional Active Carbon Electrodes with Semiconductor Particles

Supercapacitors, S-C—capacitors that take advantage of the large capacitance at the interface between an electrode and an electrolyte—have found many short-term energy applications. The parallel plate cells were made of two transparent electrodes (ITO), each covered with a semiconductor-embedded, active carbon (A-C) layer. While A-C appears black, it is not an ideal blackbody absorber that absorbs all spectral light indiscriminately. In addition to a relatively flat optical absorption background, A-C exhibits two distinct absorption bands: in the near-infrared (near-IR and in the blue. The first may be attributed to absorption by the OH− group and the latter, by scattering, possibly through surface plasmons at the pore/electrolyte interface. Here, optical and thermal effects of sub-μm SiC particles that are embedded in A-C electrodes, are presented. Similar to nano-Si particles, SiC exhibits blue band absorption, but it is less likely to oxidize. Using Charge-Discharge (CD) experiments, the relative optically related capacitance increase may be as large as ~34% (68% when the illuminated area is taken into account). Capacitance increase was noted as the illuminated samples became hotter. This thermal effect amounts to <20% of the overall relative capacitance change using CD experiments. The thermal effect was quite large when the SiC particles were replaced by CdSe/ZnS quantum dots; for the latter, the thermal effect was 35% compared to 10% for the optical effect. When analyzing the optical effect one may consider two processes: ionization of the semiconductor particles and charge displacement under the cell’s terminals—a dipole effect. A model suggests that the capacitance increase is related to an optically induced dipole effect.

Semiconductor Quantum Dots

Semiconductor particles in the range of 2-10 nm are known as quantum dots (QDs) and nano-crystals where in all the three spatial dimensions, excitons are confined. Because of very small size and special electronic properties, QDs are expected to be building blocks of many electronic and optoelectronic devices. These particles possess tunable quantum efficiency, continuous absorption spectra, narrow emission and long term photostability. These are important for various biomedical applications. In this chapter definition of semiconductor QDs, their methods of preparation and characterization along with their properties and applications have been discussed.

Фотолюминесценция низкоразмерных композитных структур полиметилметакрилат/(Zn,Cd,Mn,Eu)S

A colloidal technology for the synthesis and doping of low-dimensional structures based on zinc and cadmium sulfides directly in the medium of an acrylic monomer is implemented in the process of obtaining optically transparent compositions of polymethylmethacrylate/(Zn,Cd,Mn,Eu)S. It is shown that the photoluminescence of the compositions is associated with a system of levels of structural defects of semiconductor particles located in its band gap, which are formed during successive doping of ZnS and CdS layers with Mn2+ and Eu3+ ions, and with intraband 5D0 → 7F1,2,4 transitions of 4f-electrons of Eu3+ ions. Photoluminescence excitation it occurs as a result of the transition of electrons from the valence band of a semiconductor to the levels of defects in its structure and partial energy transfer to the excited energy levels of Eu3+ ions.

Structure-Properties Correlation of Lead Selenide-Lead Selenite Composite

The main areas of work are related to the synthesis of a two-phase composite (1-x)PbSe·xPbSeO3 in the form of a powder, faceted single crystal, film and compacted material with the possibility of changing the fraction (x) of the PbSeO3 phase from 0 to 1 by oxidation of PbSe in a dry atmosphere in the temperature range 20-550 °С and the study of its physicochemical properties. All initial samples are obtained by the original method from Pb1-ySey powder, in which the composition corresponds to the maximum melting temperature of the compound and is defined as ysmax=0.500025±0.000025 at. Se. The powder is crushed, after which homogenizing annealing is performed at a constant temperature (~750 °C) in a dynamic vacuum in order to achieve the minimum general pressure condition. The noted precursor-related technological procedures are necessary to achieve congruent evaporation conditions in all types of samples and help minimize the concentration of inherent defects and inclusions in phase two. Depending on application, it is possible to form crystalline powders with a given ratio of volumetric phases PbSe and PbSeO3 in a separate grain. For all cases, the "shell" for semiconductor particles PbSe is the dielectric phase PbSeO3. The principal possibility of forming the smallest (up to nanometer) grains of lead selenide in the dielectric matrix of lead selenite is shown. According to the proposed method, the synthesis of lead selenite by oxidation of lead selenide is possible.

Fabrication of Hybrid Membranes Containing Nylon-11 and Organic Semiconductor Particles with Potential Applications in Molecular Electronics

Chemical degradation is a major disadvantage in the development of organic semiconductors. This work proposes the manufacture and characterization of organic semiconductor membranes in order to prevent semiconductor properties decreasing. Semiconductor membranes consisting of Nylon-11 and particles of π-conjugated molecular semiconductors were manufactured by high-vacuum evaporation followed by thermal relaxation. Initially, and with the aim of obtaining semiconductor particles, bulk heterojunction (BHJ) was carried out using green chemistry techniques between the zinc phthalocyanine (ZnPc) and the zinc hexadecafluoro-phthalocyanine (F16ZnPc) as n-type molecular semiconductors with the p-type molecular semiconductor dibenzotetrathiafulvalene (DBTTF). Consequently, the π-conjugated semiconductors particles were embedded in a Nylon-11 matrix and characterized, both structurally and considering their optical and electrical properties. Thin films of these materials were manufactured in order to comparatively study the membranes and precursor semiconductor particles. The membranes presented bandgap (Eg) values that were lower than those obtained in the films, which is an indicator of an improvement in their semiconductor capacity. Finally, the membranes were subjected to accelerated lighting conditions, to determine the stability of the polymer and the operating capacity of the membrane. After fatigue conditions, the electrical behavior of the proposed semiconductor membranes remained practically unaltered; therefore, they could have potential applications in molecular electronics. The chemical stability of membranes, which did not degrade in their polymer compound, nor in the semiconductor, was monitored by IR spectroscopy.

Development of electrical enhanced photocatalysis polishing slurry for silicon carbide wafer

Single-crystal silicon carbide, as one of the most promising next-generation semiconductor materials, should be polished with atomically smooth and damage-free surface to meet the requirements of semiconductor applications. The research presented in this paper aims to develop an electrical enhanced photocatalysis polishing method for atomic smoothing of Si-face (0001) 4H-SiC wafer based on the powerful oxidability of UV photo-excited hydroxyl radical on nano semiconductor particles. The research identifies the influences of photocatalyst, electron capturer, UV light, voltage and pH value by designing the orthogonal fading experiments of methyl orange and thus develops several slurries for electrical enhanced photocatalysis polishing accordingly. It also demonstrates that photocatalyst, UV light, electron capturer, and acid environment being necessaries for the electrical enhanced photocatalysis polishing process. Electricity can effectively prevent the recombination of electrons and holes generated on the surface of semiconductor particles and therefore enhance the polishing efficiency. Five photocatalysts including 5 nm TiO2, P25, ZnO, CeO2 and ZrO2 have envious selectivity to the UV light. The slurry with P25 as the photocatalyst and H2O2 as electron capturer presents best polishing performance among, which provides a material removal rate of about 1.18 µm/h and a surface roughness of about Ra 0.0527 nm in an area of 1.0 × 1.0 µm. Furthermore, it also discusses how the UV light irradiation and electricity promotes the chemical oxidation of hydroxyl radical with SiC by forming “Si-C-O”, “Si-O” and “C-O” on SiC surface. The paper concludes that the proposed electrical enhanced photocatalysis polishing is an effective and clean manufacturing method for SiC wafer without rendering toxic chemical effect on environment and human health.