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Thin film transistors, with channels composed of In-X-Zn oxides, IXZO, with X dopants: Ga, Sb, Be, Mg, Ag, Ca, Al, Ni, and Cu, were fabricated and their I-V characteristics were taken at selected temperatures in the 77K

Alloying of In/Zn oxides with various X atoms stabilizes the IXZO structures but generates electron traps in the compounds, degrading the electron mobility, μ. To assess whether the latter is linked to the oxygen affinity or the ionic radius, of the X element, several IXZO samples are synthesized by the sol-gel process, with a large number (14) of X elements. The IXZOs are characterized by XPS, SIMS, DRX, and UV-spectroscopy and used for fabricating thin film transistors. Channel μ and the interface defect density NST, extracted from the TFT electrical characteristics and low frequency noise, followed an increasing trend and the values of μ and NST are linked by an exponential relation. The highest μ (8.5 cm²V-1s-1) is obtained in In-Ga-Zn-O, and slightly lower value for Sb and Sn-doped IXZOs, with NST≈2×1012 eV-1 cm-2, close to that of the In-Zn-O reference TFT. This is explained by a higher electronegativity of Ga, Sb, and Sn than Zn and In, their ionic radius values being close to that of In and Zn. Consequently, Ga, Sb, and Sn induce weaker perturbations of In-O and Zn-O sequences in the sol-gel process, than the X elements having lower electronegativity and different ionic radius. The TFTs with X=Ca, Al, Ni and Cu exhibited the lowest μ and NST>1013 eV-1cm-2, most likely because of metallic or oxide clusters formation. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) suffer from limitations such as low mobility of charge carriers and high access resistance. Direct and accurate evaluation of these quantities becomes crucial for understanding the OFETs properties. We introduce the Y function method (YFM) to pentacene OFETs. This method allows us to evaluate the low-field mobility without the access or contact resistance influence. The low-field mobility is shown to be more appropriate than the currently applied field-effect mobility for the OFETs’ performance evaluation. Its unique advantage is to directly suppress the contact resistance influence in individual transistors, although such contact resistance is a constant as compared to the widely accepted variable one with respect to the gate voltage. After a comparison in detail with the transmission-line method, the YFM proved to be a fast and precise alternative method for the contact resistance evaluation. At the same time, how the contact resistance affects the effective mobility and the field-effect mobility in organic transistors is also addressed. [ABSTRACT FROM AUTHOR]

Studies the effects of electrical stress on static characteristics and power spectral density, of base current, fluctuations at low frequencies, in quasiself-aligned bipolar n-p-n junction. Generation of hot carrier-induced noise sources; Uniformity and reproducibility of the degradation process.

Studies low frequency noise in quasiself-aligned bipolar n-p-n junction transistors with varying emitter/base junction dimensions. Power spectral density; Localization of the low frequency noise sources; Application of current-to-voltage converters.

In this brief, low-frequency noise (LFN) characteristics are studied in oxide-based (\TiN/\HfOx/\Pt) resistive random access nemory cells having different dimensions. It is confirmed that, for the low resistance state (LRS), current conduction is localized without an area dependence, whereas for the high resistance state, it is a uniform leakage current throughout the whole device area. An LFN model is proposed for the filamentary LRS based on the carrier number fluctuation approach, allowing physical analysis of filament characteristics and the surrounding trap concentration. [ABSTRACT FROM AUTHOR]

A review of studies on nearest-neighbour hopping (NNH) between impurities, whose ground state (GS) is degenerate or split by the application of a uniaxial stress X or a magnetic field B is presented. The case of acceptors in Ge and Si, whose GS components have different symmetry properties, is discussed in detail. A solution of the percolation problem involving all the possible transitions between the components of the acceptor GS is provided. For Ge it was preceded by a construction of the acceptor ground state wavefunctions, possessing both a correct symmetry and a correct asymptote behaviour, indispensable for evaluating probabilities of phonon-assisted NNH. For Si the energy diagrams of the accepter GS for various configurations of X and B were obtained and subsequently used in a model calculation. In both Ge and Si the calculation accounted qualitatively for the data. [ABSTRACT FROM AUTHOR]

A diagnostic procedure for the contact low-frequency noise sources of staggered organic transistors is presented. Like the conventional process for channel noise, the two models of carrier number fluctuations and Hooge mobility fluctuations are concerned. Both models apply to bis(triisopropylsilylethynyl) pentacene transistors at lower and higher current densities, where the contact defect density is 1000 times higher than that in the channel and a Hooge parameter around 1 is obtained, respectively. The Hooge mobility fluctuations model well accounts for the contact noise in pentacene transistors with a Hooge parameter in the range of 0.5-3. [ABSTRACT FROM AUTHOR]

The power spectral density of low-frequency noise in contact resistance, SRsd, of organic transistors is evaluated by the transfer-line method. The obtained gate-voltage dependent SRsd is then normalized by the square of contact resistance, which is extracted from dc current-voltage (I-V) measurements. After normalization, slightly variable and nearly constant SRsd/Rsd2 with respect to gate voltage are obtained in the range 10-7–10-6 μm/Hz at 20 Hz in p-type and n-type devices, respectively. This method proves suitable to investigate separately the origin of the noise sources in channel as well as in contact region. [ABSTRACT FROM AUTHOR]

We investigate physical mechanisms of random telegraph signal (RTS) noise in reverse base current of hot carrier-degraded polysilicon emitter bipolar junction transistors. RTS noise, analyzed in the time domain, is studied as a function of reverse base-emitter bias, temperature, and additional reverse-bias stress. Two-level RTS with a relative amplitude as high as 100% is observed at room temperature. The RTS amplitude varies exponentially with the applied reverse base-emitter voltage and depends weakly on temperature. The additional hot carrier stress is observed to induce changes in RTS amplitude and mean pulse widths (independent or correlated), and a disappearance/reappearance of the RTS fluctuations. The results are interpreted by a model where the RTS noise is caused by fluctuations of generation-recombination (g-r) parameters (i.e., capture cross sections and energy position in the gap) of a stress-induced complex bistable defect (CBD) at the Si/SiO[sub 2] interface. The complex defect is assumed to be either a two-state fast interface state or an interacting pair of a fast interface state with a slow neighboring border trap. The RTS amplitude is well explained by fluctuations in a single-defect electric-field-enhanced g-r rate between a finite value and naught. The RTS amplitude-bias characteristics and their temperature dependence are satisfactorily accounted for by an expression for a phonon-assisted tunneling current via a single deep-level state. The model parameters are the g-r parameters of the defect and its spatial position in the base-emitter p-n junction. The stress-induced changes in the RTS noise are attributed to the influence of log-time trapping of hot carriers on border states laying in the vicinity of a CBD center. The charged border traps interact with a CBD, changing both its g-r parameters and the RTS switching behavior. The variations in RTS parameters are related to the microscopic nature of the interaction and are discussed f... [ABSTRACT FROM AUTHOR]

We studied electrical parallel and perpendicular transport in thin epitaxial erbium silicide films obtained by solid phase reaction and by codeposition of Er and Si on (111) Si. Resistivity measurements show that the silicide is metallic with a room-temperature resistivity of 34 μΩ cm; the dependence of the Hall coefficient on temperature can be explained by a two-band conduction model. Magnetic effects are shown to affect the low-temperature resistivity and the Hall coefficient. Perpendicular transport properties are studied by electrical [current-voltage I(V) and capacitance-voltage C(V) characteristics] and internal photoemission methods on erbium silicide/n- or p-type Si diodes. The p-type diodes have a perfect rectifying behavior with a Schottky barrier height of about 0.74 eV measured by I(V) and photoemission methods. The n-type junction is ohmic at room temperature and rectifying at low temperatures; C(V) and optical measurements yield a Schottky barrier height of about 0.28 eV. Some potential applications of erbium silicide/Si heterostructures are presented. [ABSTRACT FROM AUTHOR]

We prepared Er silicide films on (111) Si by (1) deposition of Er and contact reaction at 380 °C or (2) vacuum codeposition of Er and Si maintaining the flux ratio close to 1:2. Subsequent annealing at temperatures up to 900 °C yielded monocrystalline, continuous layers, whose properties were examined by means of low-energy electron diffraction, Auger spectroscopy (in situ) and (ex situ), x-ray and high-energy electron diffraction, and Rutherford backscattering. Method 2 was shown to give better results. The films had a hexagonal AlB2 structure with Si deficiency up to 20%, which is consistent with formerly published results on Si vacancy formation. We showed that the film structure had an additional periodicity of 15 Å along the <110> orientations of Si and of 6 Å along the <112> orientations of Si. We demonstrated a feasibility of Si reepitaxy on Er silicide deposited on (111) Si, thus fabricating a novel semiconductor/metal/semiconductor epitaxial heterostructure. [ABSTRACT FROM AUTHOR]

Abstract: We propose a novel influenza vaccine composed of the adenovirus dodecahedron (Dd) as delivery platform carrying an internal influenza matrix protein M1. To attach the antigen to the vector we used WW domains interacting with Dd. Successful internalization of the Dd-M1WW complex was observed using biochemical and cell biology techniques. We show here that the complex of Dd with antigen is a potent activator of human myeloid dendritic cells (MDC), and that it is efficiently presented by MDC to M1-specific CD8+ T lymphocytes. These results show that proposed vaccine model is feasible and that adenovirus dodecahedron is a potent delivery platform for foreign antigens to human cells. [Copyright &y& Elsevier]

Abstract: Potyvirus RNA contains at the 5′ end a covalently linked virus-encoded protein VPg, which is required for virus infectivity. This role has been attributed to VPg interaction with the eukaryotic translation initiation factor eIF4E, a cap-binding protein. We characterized the dissociation constants for the interaction of the potato virus Y VPg with different plant eIF4Es and its isoforms and mapped the eIF(iso)4E attachment region on VPg. VPg/eIF4E interaction results in the inhibition of cell-free protein synthesis, and we show that it stems from the liberation of the cap moiety from the complex with eIF4E. Since VPg does not attach the cap, it appears that VPg induces changes in the eIF4E structure, diminishing its affinity to the cap. We show here that the initiation complex scaffold protein eIF(iso)4G increases VPg interaction with eIF(iso)4E. These data together suggest similar cap and VPg interactions with eIF4E and characterize VPg as a novel eIF4E-binding protein, which inhibits host protein synthesis at a very early stage of the initiation complex formation through the inhibition of cap attachment to the initiation factor eIF4E. [Copyright &y& Elsevier]

The sub-viral dodecahedral particle of human adenovirus type 3, composed of the viral penton base and fiber proteins, shares an important characteristic of the entire virus: it can attach to cells and penetrate them. Structure determination of the fiberless dodecahedron by cryo-electron microscopy to 9Å resolution reveals tightly bound pentamer subunits, with only minimal interfaces between penton bases stabilizing the fragile dodecahedron. The internal cavity of the dodecahedron is ∼80Å in diameter, and the interior surface is accessible to solvent through perforations of ∼20Å diameter between the pentamer towers. We observe weak density beneath pentamers that we attribute to a penton base peptide including residues 38–48. The intact amino-terminal domain appears to interfere with pentamer–pentamer interactions and its absence by mutation or proteolysis is essential for dodecamer assembly. Differences between the 9Å dodecahedron structure and the adenovirus serotype 2 (Ad2) crystallographic model correlate closely with differences in sequence. The 3D structure of the dodecahedron including fibers at 16Å resolution reveals extra density on the top of the penton base that can be attributed to the fiber N terminus. The fiber itself exhibits striations that correlate with features of the atomic structure of the partial Ad2 fiber and that represent a repeat motif present in the amino acid sequence. These new observations offer important insights into particle assembly and stability, as well as the practicality of using the dodecahedron in targeted drug delivery. The structural work provides a sound basis for manipulating the properties of this particle and thereby enhancing its value for such therapeutic use. [Copyright &y& Elsevier]

Abstract: Adenovirus penton is a non-covalent complex composed of the penton base and fiber proteins, localized at the twelve vertices of the icosahedral virus capsid. In cells infected by adenovirus serotype 3 (Ad3), penton is found not only in the virus capsid but also self-assembled in dodecahedra formed through interactions between the twelve penton bases. In this study, the intracellular trafficking of penton proteins from the cytoplasm to the nucleus has been followed, and the nuclear re-arrangement induced by viral infection has been observed by electron microscopy of ultrathin sections. The amount of dodecahedra has been assessed in relation to the number of Ad3 infectious virions produced during the Ad3 replication cycle. It appears that dodecahedra are produced in a large excess over viral infectious particles and that they are located intranuclearly along the nuclear membrane of Ad3-infected cells at late times of infection. [Copyright &y& Elsevier]

Adenovirus dodecahedron is a virus-like particle composed of only two viral proteins of human adenovirus serotype 3 that are responsible for virus attachment and internalization. We show here that this dodecameric particle, devoid of genetic information, efficiently penetrates human cells and can deliver large multimeric proteins such as immunoglobulins. [ABSTRACT FROM AUTHOR]