Influence of Ultrasonic Waves on Current-Voltage Characteristics and Polarization Effects of Si-N-P Radiation Receivers

The currents of n-p junctions and polarization effects caused by the capture processes of diffusion Si-receivers (detectors) of radiation exposed by ultrasound have been analyzed in this work. It was found that there are local concentrations of impurity atoms with an effective size l>6μm30μm in Si-n-p radiation receivers. They determine the behavior of the signal amplitude in different intervals of electric and temperature fields. It was found that at Е>1500V/cm and T>168K, the efficiency of collecting nonequilibrium charge carriers significantly increases and doublets of spectral α-lines and “humps” disappear at the temperature dependences of the signal amplitude. The main physical processes and mechanisms that determine the appearance of the phenomenon of "polarization" of Si-n-p-detectors were investigated. This phenomenon is caused by the existence of local gold atoms, which arise in the process of manufacturing technology of Si-n-p-receivers and act as effective trapping centers.

Effect of Point Defects on Electronic Properties and Structure of Talc (001) Surface by First Principles

The surface structure and electronic properties of Mg vacancy defects on talc (001) and impurity defects with Fe, Mn, Ni, Al, and Ca replacing Mg atoms were calculated by using density functional theory. The calculation results show that the order of impurity substitution energy is Mn < Ni < Al < Ca < Fe. This indicates that Fe impurity defects are most easily formed in talc crystals. The covalent bonding between Si atoms and reactive oxygen atoms adjacent to impurity atoms is weakened and the ionic property is enhanced. The addition of Fe, Mn, and Ni atoms makes the surface of talc change from an insulator to a semiconductor and enhances its electrical conductivity. The analysis of electron state density shows that surface states composed of impurity atoms 4S orbital appear near the Fermi level.

Спонтанный спиновый магнетизм донорных электронов проводимости гибридизированных состояний кристалла, образованных системой примесных атомов 3d-элементов низкой концентрации (<1 at.%)

The given work is devoted to the experimental proof of existing the spontaneous spin polarization of the donor electron system of 3d-transition element impurity atoms of low concentration (<1 at.%) in a mercury selenide crystal. For this purpose there have been measured the dependences of the magnetization on the magnetic field strength. As a result of the analysis of the obtained dependences, there were extracted the impurity contributions, which are described by the magnetization curves typical of the ferromagnets, and by the magnetic parameters conforming to the spontaneous magnetism of the systems under study, which are unambiguously related to the donor conduction electrons of the outer d-shells of impurity atoms. By its nature, according to the developed theoretical concepts, the spontaneous spin polarization manifests itself in exchange interaction, taking place in hybridizing the electronic states of the impurity atom and the conduction band ones of the crystal.

DFT Based Material Computations of Metal-doped and Pure Carbon Nanodots for Examining their Enhancement of Sulfur Dioxide Adsorption

Carbon nanodots, one of the last members of the nanocarbon family, show superior properties, such as low-cost production, good conductivity, and optical properties, nontoxic behavior, high biocompatibility, and eco-friendly nature. Understanding the effect of metal doping on the modification of the electronic structure of carbon nanodots is critical for enlarging its potential applications. In the present study, in terms of structural, energetic, and electronic analyses, X-doped carbon nanodot structures (X = B, N, Si, Al, Co, Au, Pd, and Pt) and their SO2 adsorption abilities were examined comprehensively by employing DFT. Results depict that embedding the heavy impurity metals (Pd, Pt) to the nanodot structures does not improve the SO2 sensing ability of carbon nanodot materials relatively. However, the doping of the low concentrated metals to the carbon nanodots may be one of the best ways for enhancing the SO2 trapping ability of the carbon nanodot materials since the calculated results having high adsorption energy values indicate SO2 gas molecule is easily adsorbed on the surface of doped carbon nanodots. This means higher adsorption capability compared to pure ones. Thus, it is suggested that the doped carbon nanodots consisting of B, Si, and N impurity atoms may be good candidates for effective SO2 sensing (adsorptions).

Quantum interference effects in multi-channel correlated tunneling structures

In multi-channel tunneling systems quantum interference effects modify tunneling conductance spectra due to Fano effect. We investigated the impact of Hubbard type Coulomb interaction on tunneling conductance spectra for the system formed by several interacting impurity atoms or quantum dots localised between the contact leads. It was shown that the Fano shape of tunneling conductance spectra strongly changes in the presence of on-site Coulomb interaction between localised electrons in the intermediate system. The main effect which determines the shape of the tunneling peaks could be not Fano interference but mostly nonequilibrium dependence of the occupation numbers on bias voltage.

Formation of complexes consisting of impurity Mn atoms and group VI elements in the crystal lattice of silicon

Formation of complexes of impurity Mn atoms with impurity atoms of group VI elements (S, Se, Te) in the silicon crystal lattice has been studied. It has been experimentally found that formation of electrically neutral molecules with an ionic-covalent bond between Mn atoms and group VI elements takes place, which possibly leads to formation of new Si2BVI++Mn binary unit cells in the silicon crystal lattice. It has been shown that in the samples Si<S, Mn>, Si<Se, Mn> and Si<Te, Mn>, an intense complex formation occurs at the temperatures 1100, 820 and 650°C, respectively.

Influence of Mg Content on Texture Development during Hot Plain-Strain Deformation of Aluminum Alloys

The study addresses the effect of magnesium and other alloying elements on rolling “β-fiber” texture formation during hot deformation of aluminum alloys. For the study, flat cast ingots from three aluminum alloys with variable magnesium content were deformed in a Gleeble testing unit with different parameters of thermomechanical treatment. Immediately after completion of deformation, the samples were quenched using an automatic cooling system and the microstructure and crystalline texture was analyzed by optical microscopy and X-ray analysis. The analysis demonstrated that an increase in alloying components, magnesium in particular, leads to an increase in brass-type texture and a decrease in S and copper-type texture. The reason was that the simulation of the deformation texture development revealed a great contribution of impurity atoms rather than the decrease in stacking fault energy.