Analysis of light-induced degradation mechanisms in α-Si:H/μc-Si:H solar photovoltaics

The photoinduced degradation of the i-α-Si:H layer in tandem photovoltaic converters based on α-Si:H/μc-Si:H structures is analyzed in terms of the “H-collision-” and “floating-bond” models and modifications of these. It is shown that the form of the degradation dependence is well described by all models under consideration. Compared with the modified models, the original “H-collision-” and “floating-bond” models yield estimates for saturated dangling-bond concentrations, which are always dependent on the intensity of the light that caused the degradation. The modified “floating-bond” model makes it possible to exclude this dependence, and the modified “H-collision” model describes the occurrence of this dependence in a certain range of illumination intensities and its absence in another range, which is in best agreement with experimental data.     

Sense standards,recognition of textual information and its compression based on knowledge of synonymy

This paper presents a method for revelation a sense standard based on a set of semantically equivalent phrases of a subject-oriented language as a foundation for text recognition and compression. It suggests using this method to organize the basic components of a software knowledge control system based on test tasks of the open form.     

Study of the mechanisms of barrier discharge development in the needle–plane system

The dielectric barrier discharge (DBD) was studied in three experimental configurations: “needle–polymer barrier–plane”, “needle–submillimeter air gap–polymer barrier–plane,” and“needle–submillimeter air gap–metal disk–polymer barrier–plane”. In the first case, only the DBD surface phase occurred (i.e., surface discharge), in the second case both surface and volume phases took place (i.e., typical DBD), and in the third case only the volume phase occurred (i.e., air–gap breakdown). A polyethylene terephthalate film 100 μm thick was used as a barrier. The discharge voltage, the discharge current pulse, the transferred charge, and the spatial distribution of the surface charge density were measured during the experiments. It was experimentally shown that the surface phase of the DBD has a substantial impact on the whole discharge process. The data indicate that the placement of a metal disk with a floating potential on the barrier surface causes the initiation of an atmospheric pressure glow discharge.     

Integral characteristics of a porous gas axial bearing

A flat axial bearing with pressurized gas supply through an annular flow valve made from anisotropic porous material is considered. The differential equation for the pressure in the lubricant layer adjacent to the porous wall is numerically solved using the Runge-Kutta method, with two boundary conditions taken into account. One of these, which is integral, has remained out of sight in the porous support analysis until recently. An algorithm for calculating the lifting force and rigidity of support as well as mass rate of gas flow through this support is presented. The optimization of support is performed, and conclusions are drawn as to its influence on different factors.     

Modification of the structure and hydrogen content of amorphous hydrogenated silicon films under conditions of femtosecond laser-induced crystallization

We have studied the Raman spectra of initially amorphous hydrogenated silicon (a-Si:H) films upon their exposure to femtosecond laser-radiation pulses with the fluence varied within 30–155 mJ/cm². The distribution of the volume fraction of a crystalline phase over the surface of processed films is determined for the first time and a correlation is established between changes in this value and the hydrogen content in a-Si:H films upon the crystallization induced by femtosecond laser radiation.     

Dielectric Properties of Oligonucleotides on the Surface of Si Nanosandwich Structures

Planar silicon nanostructures that are formed as a very narrow silicon quantum well confined by delta-barriers heavily doped with boron are used to study the dielectric properties of DNA oligonucleotides deposited onto the surface of the nanostructures. The capacitance characteristics of the silicon nanostructures with oligonucleotides deposited onto their surface are determined by recording the local tunneling current- voltage characteristics by means of scanning tunneling microscopy. The results show the possibility of identifying the local dielectric properties of DNA oligonucleotide segments consisting of repeating G–C pairs. These properties apparently give grounds to correlate the segments with polymer molecules exhibiting the properties of multiferroics.     

Heteroepitaxy of AIIIBV films on vicinal Si(001) substrates

GaAs films on Si substrates miscut from the (001) plane by 6° in the [110] direction are grown by molecular beam epitaxy (MBE). GaAs films are grown both on the Si surface terminated by arsenic atoms and on thin pseudomorphic GaP/Si layers. The condition of formation of the As sublayer and the first monolayer of GaP on the Si surface is defined as the GaAs film orientation (001) or \((00\bar 1)\) . The processes of Si surface preparation and formation of the As sublayer and GaAs and GaP epitaxial layers are monitored by means of high-energy electron diffraction reflection (RHEED). The grown structures are investigated by methods of X-ray diffraction, atomic force microscopy (ATM), high-resolution transmission electron microscopy (HRTEM), and low-temperature luminescences. It is shown that the epitaxial film orientation affects both the surface morphology and its crystalline properties. Intense photoluminescence is obtained from the In_0.17Ga_0.83As quantum well structure grown on the GaAs/Si buffer layer.     

Capacitive Characteristics of High-Speed Photovoltaic Converters at Combined Lighting

Semiconductors - p–i–n GaAs photovoltaic converters of modulated laser radiation (810–830 nm) transferring both energy (laser power) and information signal were developed. The...