Electric Current and Noise in Long GaN Nanowires in the Space-Charge Limited Transport Regime

We studied electric current and noise in planar GaN nanowires (NWs). The results obtained at low voltages provide us with estimates of the depletion effects in the NWs. For larger voltages, we observed the space-charge limited current (SCLC) effect. The onset of the effect clearly correlates with the NW width. For narrow NWs the mature SCLC regime was achieved. This effect has great impact on fluctuation characteristics of studied NWs. At low voltages, we found that the normalized noise level increases with decreasing NW width. In the SCLC regime, a further increase in the normalized noise intensity (up to 1E4 times) was observed, as well as a change in the shape of the spectra with a tendency towards slope -3/2. We suggest that the features of the electric current and noise found in the NWs are of a general character and will have an impact on the development of NW-based devices.Comment: 12 pages, 4 figures in Fluctuation and Noise Letters (2017

Noise and Transport Characterization of Single Molecular Break Junctions with Individual Molecule

We studied the noise spectra of molecule-free and molecule-containing mechanically controllable break junctions. Both types of junctions revealed typical 1/ f noise characteristics at different distances between the contacts with square dependence of current noise power spectral density on current. Additional Lorentzian-shape (1/ f 2) noise components were recorded only when nanoelectrodes were bridged by individual 1,4 benzenediamine molecule. The characteristic frequency of the revealed 1/ f 2 noise related to a single bridging molecule correlates with the lock-in current amplitudes. The recorded behavior of Lorentzian-shape noise component as a function of current is interpreted as the manifestation of a dynamic reconfiguration of molecular coupling to the metal electrodes. We propose a phenomenological model that correlates the charge transport via a single molecule with the reconfiguration of its coupling to the metal electrodes. Experimentally obtained results are in good agreement with theoretical ones and indicate that coupling between the molecule metal electrodes is important aspect that should be taken into account.Comment: 15 pages, 7 figure

Mushrooms Red Book of Ukraine in Culture. 1. Patterns of Growth Hericium coralloides

На території НПП «Гуцульщина» виявлено лише три локалітети Hericium coralloides – гриба, занесеного до Червоної книги України. У результаті проведених досліджень виділено в чисту культуру аборигенний штам К01. Як для виділення, так і для підтримки та забезпечення життєздатності гриба в культурі картопельно-глюкозний агар виявився оптимальним серед апробованих середовищ. Індивідуальні особливості росту H. coralloides К01 вказують на вузькі трофічні можливості цього штаму при поверхневому культивуванні, оскільки з п’яти апробованих середовищ придатними для росту виявилися лише два. Цей штам гриба вважаємо перспективним для використання як інокулянта відповідних субстратів у природному середовищі, оскільки для нього характерні високі показники радіального росту, короткий період log-фази та утворення в чистій культурі стадії телеоморфи. The national park «Hutsulshchyna» found only three localities of Hericium coralloides − mushroom Red Book of Ukraine. The result of the research was to obtain in a pure culture of the native strain K01. As for the release, and to support and ensure the viability of the fungus in culture potato - glucose agar was the best among the tested environments. Individual features of the growth of H. coralloides K01 indicate the narrow trophic features of this strain at cultivation because from five tested media suitable for growth were only two. This strain K01 H. coralloides may be considered promising for use as an inoculant respective substrates in the environment , because it is characterized by high rates of radial growth , a short period of log- phase and ability to form stage teleomorfy in pure culture.Роботу виконано у НПП «Гуцульщина», ННЦ «Інститут біології» КНУ ім. Т. Шевченк

Hacia un nuevo socialismo

Nos encontramos ante el testamento político de uno de los líderes norteamericanos del socialismo democrático. M. Harrington murió en agosto de 1989 poco después de haber aparecido este libro. Intuyendo su próximo final hace Un balance histórico del movimiento socialista y apunta hacia su potencial futuro. Es el testamento de un militante y un intelectual que reflexiona sobre lo que es el socialismo desde Estados Unidos, la sociedad occidental del capitalismo más desarrollada y más refractaria a la tradición socialista.Peer reviewe

Dynamic redistribution of the electric field of the channel in AlGaN/GaN high electron mobility transistor with nanometer-scale gate length

Transport peculiarities and the physical origin of noise properties in AlGaN/GaN-based high electron mobility transistors (HEMTs) with a large ratio of channel length to gate length were investigated. Dependence of deviations of low-frequency noise spectra from the 1/f law on applied gate voltages was studied in an extended range of frequencies. The behavior is explained in terms of a model based on the dynamic redistribution of the electric field along the two-dimensional channel of the HEMT. The results show that the main contribution to the noise originates from the region under the gate and adjacent to the gate channel regions. (C) 2005 American Institute of Physics

Low-frequency Noise in Individual Carbon Nanotube Field-Effect Transistors with Top, Side and Back Gate Configurations: Effect of Gamma Irradiation

We report on the influence of low gamma irradiation (10^4 Gy) on the noise properties of individual carbon nanotube (CNT) field-effect transistors (FETs) with different gate configurations and two different dielectric layers, SiO2 and Al2O3. Before treatment, strong generation-recombination (GR) noise components are observed. These data are used to identify several charge traps related to dielectric layers of the FETs by determining their activation energy. Investigation of samples with a single SiO2 dielectric layer as well as with two dielectric layers allows us to separate traps for each of the two dielectric layers. We reveal that each charge trap level observed in the side gate operation splits into two levels in top gate operation due to a different potential profile along the CNT channel. After gamma irradiation, only reduced flicker noise is registered in the noise spectra, which indicates a decrease of the number of charge traps. The mobility, which is estimated to be larger than 2x10^4 cm2V-1s-1 at room temperature, decreases only slightly after radiation treatment demonstrating high radiation hardness of the CNTs. Finally, we study the influence of Schottky barriers at the metal-nanotube interface on the transport properties of FETs analyzing the behavior of the flicker noise component.Comment: 19 pages, 9 figures, 1 table, accepted for publication in "Nanotechnology" journa

Thermal, dielectrical and mechanical response of α and β-poly(vinilydene fluoride)/Co-MgO nanocomposites

Nanocomposites of the self-forming core-shell Co-MgO nanoparticles, which were of approximately 100 nm in diameter, and poly(vinylidene fluoride) (PVDF) polymer have been prepared. When the polymer is crystallized in the α-phase, the introduction of the nanoparticles leads to nucleation of the γ-phase of PVDF, increasing also the melting temperature of the polymer. With the introduction of the Co-MgO particles, the dielectric constant of the material slightly increases and the storage modulus decreases with respect to the values obtained for the pure polymer