Large Negative Shift Research Articles

Influences of Gate Bias and Light Stresses on Device Characteristics of High-Energy Electron-Beam-Irradiated Indium Gallium Zinc Oxide Based Thin Film Transistors

Under white light illumination, amorphous indium–gallium–zinc oxide (a-IGZO)-based thin-film transistors (TFTs) showed a large negative shift of threshold voltage of more than -15 V depending on the process conditions. We investigated the influences of both gate bias and white light illumination on device properties of IGZO-based TFTs untreated and treated with high-energy electron beam irradiation (HEEBI). The TFTs were treated with HEEBI in air at room temperature (RT), electron beam energy of 0.8 MeV, and a dose of 1×1014 electrons/cm2. The HEEBI-treated TFTs showed an improved stability under negative bias illumination stress (NBIS) and positive bias illumination stress (PBIS) compared with non-HEEBI-treated TFTs, suggesting that the acceptor-like defects might be generated by HEEBI treatment near the valence band edge.

BK potassium channel modulation by leucine-rich repeat-containing proteins

Molecular diversity of ion channel structure and function underlies variability in electrical signaling in nerve, muscle, and nonexcitable cells. Regulation by variable auxiliary subunits is a major mechanism to generate tissue- or cell-specific diversity of ion channel function. Mammalian large-conductance, voltage- and calcium-activated potassium channels (BK, K(Ca)1.1) are ubiquitously expressed with diverse functions in different tissues or cell types, consisting of the pore-forming, voltage- and Ca(2+)-sensing α-subunits (BKα), either alone or together with the tissue-specific auxiliary β-subunits (β1-β4). We recently identified a leucine-rich repeat (LRR)-containing membrane protein, LRRC26, as a BK channel auxiliary subunit, which causes an unprecedented large negative shift (∼140 mV) in voltage dependence of channel activation. Here we report a group of LRRC26 paralogous proteins, LRRC52, LRRC55, and LRRC38 that potentially function as LRRC26-type auxiliary subunits of BK channels. LRRC52, LRRC55, and LRRC38 produce a marked shift in the BK channel's voltage dependence of activation in the hyperpolarizing direction by ∼100 mV, 50 mV, and 20 mV, respectively, in the absence of calcium. They along with LRRC26 show distinct expression in different human tissues: LRRC26 and LRRC38 mainly in secretory glands, LRRC52 in testis, and LRRC55 in brain. LRRC26 and its paralogs are structurally and functionally distinct from the β-subunits and we designate them as a γ family of the BK channel auxiliary proteins, which potentially regulate the channel's gating properties over a spectrum of different tissues or cell types.

Experimental observation of the spin Hall effect of light on a nanometal film via weak measurements

We theorize the spin Hall effect of light (SHEL) on a nano-metal film and demonstrate it experimentally via weak measurements. A general propagation model to describe the relationship between the spin-orbit coupling and the thickness of the metal film is established. It is revealed that the spin-orbit coupling in the SHEL can be effectively modulated by adjusting the thickness of the metal film, and the transverse displacement is sensitive to the thickness of metal film in certain range for horizontal polarization light. Importantly, a large negative transverse shift can be observed as a consequence of the combined contribution of the ratio and the phase difference of Fresnel coefficients.

Oxidation of Highly Unstable <4 nm Diameter Gold Nanoparticles 850 mV Negative of the Bulk Oxidation Potential

Here we describe the oxidation of <4 nm diameter Au nanoparticles (NPs) attached to indium tin oxide-coated glass electrodes in Br(-) and Cl(-) solution. Borohydride reduction of AuCl(4)(-) in the presence of hexanethiol or trisodium citrate (15 min) led to Au NPs <4 nm in diameter. After electrochemical and ozone removal of the hexanthiolate ligands from the thiol-coated Au NPs, Au oxidation peaks appeared in the range 0-400 mV vs Ag/AgCl (1 M KCl), which is 850-450 mV negative of the bulk Au oxidation peak near 850 mV. The oxidation potential of citrate-coated Au NPs is in the 300-500 mV range and those of 4 and 12 nm diameter Au NPs in the 660-780 mV range. The large negative shift in potential agrees with theory for NPs in the 1-2 nm diameter range. The oxidation potential of Au in Cl(-) solution is positive of that in Br(-) solution, but the difference decreases dramatically as the NP size decreases, showing less dependence on the halide for smaller NPs.

Does the global stratigraphic reproducibility of δ13C in Neoproterozoic carbonates require a marine origin? A Pliocene–Pleistocene comparison

The large and systematic negative shifts in the δ 13 C values (>12‰) of carbonate-dominated rocks that preceded Neoproterozoic glacial successions have been interpreted to record a dramatic series of global environmental and evolutionary events. These values are widely considered to be marine rather than diagenetic in origin because stratigraphic patterns of change are systematic and reproducible from basin to basin, distinct in magnitude, and associated with recognizable stratigraphic markers such as glacial deposits. In contrast, diagenetic systems are commonly considered to have a more local and stochastic influence on δ 13 C values. Cores taken in Quaternary carbonate platform sediments, however, reveal a curious similarity in magnitude, thickness, and core to core reproducibility where diagenetic alteration has occurred in response to sea-level fall. Sea-level changes produced similar δ 13 C and δ 18 O stratigraphic records at globally disparate locations, which are unrelated to the global marine δ 13 C signal and bear no relation to the global carbon cycle. By analogy with the Pliocene–Pleistocene, we propose that spatial reproducibility of δ 13 C in some Neoproterozoic successions might be attributed to causes other than secular variation of the global carbon cycle, including diagenesis. This observation does not negate the stratigraphic utility of the carbon isotopic values, only the origin of the signal.

BK Channel Modulation by Leucine-Rich Repeat Containing Proteins

Molecular diversity of ion channel structure and function underlies variability in electrical signaling in nerve, muscle, and non-excitable cells. Regulation by variable auxiliary subunits is a major mechanism to generate tissue- or cell-specific diversity of ion channel function.Mammalian large-conductance, voltage and calcium-activated potassium (BK, KCa1.1) channels are ubiquitously expressed with diverse functions in different tissues or cell types, consisting of the pore-forming, voltage- and Ca2+-sensing α-subunits (BKα), or together with the tissue-specific auxiliary subunits, previously known as four β-subunits (β1 - β4). We previously identified a leucine-rich repeat (LRR) containing protein, LRRC26, as a new type of BK channel auxiliary subunit, which causes an unprecedented large negative shift in voltage dependence of channel activation. Here we report a group of LRRC26 paralogous proteins LRRC52, LRRC55 and LRRC38 that potentially function as LRRC26-type auxiliary subunits of BK channels. LRRC52, LRRC55 and LRRC38 produce marked shifts in the BK channel's voltage dependence of activation in hyperpolarization direction to different extents. They together with LRRC26 show distinct expression in different human tissues and may have a broad influence of the BK channel function in different tissues or cell types.

β-detected NMR Study of Semi-Insulating GaAs

Abstract A beta-detected NMR experiment is carried out on a semi-insulating GaAs crystal using a low energy spin polarized 8 Li + beam to investigate the magnetic properties as a function of temperature and depth. The range of depths probed, from ∼137 nm down to ∼17 nm, coincides with the region of electronic band-bending due to the surface. We find a resonance broadened by the host nuclear dipoles, consistent with an earlier report[6], but using a pulsed radio frequency scheme, we are able to make higher resolution measurements. We find a small negative shift of the resonance (relative to an MgO reference) at room temperature that is independent of depth. Remarkably, as the temperature is reduced below about 150 K, the resonance shifts negatively and becomes depth dependent, with a larger negative shift deeper into the sample. This shift saturates below 10 K, i.e. it does not follow a Curie's law that might be expected for dilute magnetic impurities. Possible origins are discussed.

Intermolecular Hydrogen-Bond Networks and Physical Properties of BF4– and TCNQ•– Salts of Three-Fold Symmetric Tris(alkylamino)phenalenyliums

Synthesis, redox properties, and crystal structures of tris(alkylamino)phenalenyliums (TAP) having alkyl groups (n-Pr, i-Pr, t-Bu) and their charge-transfer salts with tetracyanoquinodimethane radical anion (TCNQ•–) were investigated. The electrochemical measurements revealed that TAP exhibits two irreversible reduction processes to neutral radical and anion species. The introduction of an alkylamino group caused a large negative shift of the first reduction potential and a significant decrease of the on-site Coulomb repulsion because of the electron-donating nature of amino groups and the extension of the π-electronic system. In the crystal structures of the BF4– salts, the TAP skeleton possesses a nearly 3-fold symmetric molecular plane indicating the delocalization of positive charge. The face-to-face stack of TAP formed π-dimer or columnar structures, which were connected through intermolecular N–H···F hydrogen bonds with BF4– to construct multidimensional network structures. The TCNQ•– salts prepared by the metathesis method were characterized as fully ionic salts with a 1:1 component ratio. In the crystal structures, both TAP and TCNQ•– molecules formed π-dimers, and the intermolecular hydrogen bonds between TAP and TCNQ•– constructed a two-dimensional sheet.

Recessive Loss-of-Function Mutation in the Pacemaker HCN2 Channel Causing Increased Neuronal Excitability in a Patient with Idiopathic Generalized Epilepsy

The hyperpolarization-activated I(h) current, coded for by hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, controls synaptic integration and intrinsic excitability in many brain areas. Because of their role in pacemaker function, defective HCN channels are natural candidates for contributing to epileptogenesis. Indeed, I(h) is pathologically altered after experimentally induced seizures, and several independent data indicate a link between dysfunctional HCN channels and different forms of epilepsy. However, direct evidence for functional changes of defective HCN channels correlating with the disease in human patients is still elusive. By screening families with epilepsy for mutations in Hcn1 and Hcn2 genes, we found a recessive loss-of-function point mutation in the gene coding for the HCN2 channel in a patient with sporadic idiopathic generalized epilepsy. Of 17 screened members of the same family, the proband was the only one affected and homozygous for the mutation. The mutation (E515K) is located in the C-linker, a region known to affect channel gating. Functional analysis revealed that homomeric mutant, but not heteromeric wild-type/mutant channels, have a strongly inhibited function caused by a large negative shift of activation range and slowed activation kinetics, effectively abolishing the HCN2 contribution to activity. After transfection into acutely isolated newborn rat cortical neurons, homomeric mutant, but not heteromeric wild type/mutant channels, lowered the threshold of action potential firing and strongly increased cell excitability and firing frequency when compared with wild-type channels. This is the first evidence in humans for a single-point, homozygous loss-of-function mutation in HCN2 potentially associated with generalized epilepsy with recessive inheritance.

Fe porphyrins Revisited: Synthesis, Characterization and the Effects of Ortho and Meta Fe(III) N-Alkylpyridylporphyrins Upon the Growth of E. Coli in the Presence and Absence of Ascorbate

Fe porphyrins Revisited: Synthesis, Characterization and the Effects of Ortho and Meta Fe(III) NAlkylpyridylporphyrins Upon the Growth of E. Coli in the Presence and Absence of Ascorbate Artak Tovmasyan, Tin Weitner, Ivan Spasojevic, Zrinka Rajic, Ludmil Benov, and Ines Batinic-Haberle Duke University Medical Center, USA, Faculty of Medicine, Kuwait School of Medicine, Kuwait Earlier studies indicated that at concentrations where Mn porphyrins (MnPs) are protective to SOD-deficient E. coli, Fe porphyrins (FePs) were toxic. Given the possible release of iron from FeP, and subsequent Fenton chemistry-directed OH radical production, over years we concentrated on MnPs only. However recent intriguing data tempted us to revisit FePs. Series of ortho and meta Fe(III) N-alkylpyridylporphyrins (alkyl = methyl, ethyl, butyl, hexyl, octyl) were synthesized and characterized. Metalcentered reduction potentials of ortho isomers, E1/2 are more positive than of their respective meta analogs. Similar “ortho” effect, already observed for analogous MnPs was attributed to stronger electron-withdrawing properties of the pyridyl nitrogens situated closer to the metal center. Large negative shift of E1/2 upon the increase of pH from 2 to 7.8 was observed for all complexes, and is associated with the predominance of FeP(OH) complexes in neutral solutions. Electrochemical data allow us to calculate the size of the ionic cavity formed by FePs where reactions of interest occur. the kcat (O2), obtained at pH 7.8, are higher with both ortho and meta FePs than with isomeric MnPs. Under same conditions, E1/2 values are somewhat lower for ortho FePs, but nearly twice higher for meta FePs, when compared to analogous MnPs. Consequently, the difference in kcat between ortho and meta FePs is smaller than between isomeric MnPs. the relationship between E1/2 for the FeP/FeP redox couple and kcat shows a behavior different from the one established for MnPs and is related to the differences in the type of axial ligands; at pH 7.8 there is hydroxo ligand at the Fe site and aqua ligand at the Mn site. FeP(OH) lacks positive charge at the metal site, but trans-effect makes it more reactive than MnP(H2O). With MnPs, the kcat decreases from methyl to butyl (as the steric hindrance of O2 approach increases), and increases beyond butyl as the continuous increase in E1/2 outbalances the unfavorable steric effects. With FePs though, kcat continuously decreases as the alkyl chains lengthen; the increase in E1/2 from butyl to hexyl is too small to overcome the unfavorable hindrance exerted by long alkyl chains. the results show that the differences in the axial coordination of the metal site play critical role in the thermodynamics and kinetics of O2 catalysis. Preliminary E. coli data show an intriguing behavior of FePs. Their toxicity to wild type and SOD-deficient strains is reverted in the presence of ascorbate; under identical conditions, ascorbate makes MnPs toxic. This effect may be also attributed to the differences in the Fe and Mn coordination chemistry. Studies are in progress to evaluate the therapeutic potential of FePs.

Effects of low-temperature ozone annealing on operation characteristics of amorphous In–Ga–Zn–O thin-film transistors

Effects of low-temperature annealing were examined for amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). In a previous study, we reported that O2 annealing is effective to improve performances of a-IGZO TFTs when annealed at ≥300°C, but causes large negative threshold voltage shift when annealed at ≤ 200°C. Here, we examined effects of ozone (O3) annealing on physical properties and TFT characteristics of a-IGZO in comparison with conventional O2 annealing. We found little differences in chemical composition, band gap and photoemission spectra between the O2 and the O3 annealed films. On the other hand, free electron density was suppressed well by the O3 annealing even at low temperatures ≤200°C. Moreover, even at 150°C, the TFTs characteristics were improved to the subthreshold voltage swing of 217mV/decade, the saturation mobility of ~11.4cm2(Vs)−1 and the threshold voltage of 0.1V by the O3 annealing. It was also found that the effects of the O3 annealing is more effective for thicker channel TFTs, which would be due to stronger oxidation power and the larger diffusion constant of oxygen atoms produced from O3 molecules than those of O2. These results substantiate that the O3 annealing is more effective to improve TFT characteristics in particular for low-temperature processes at ≤200°C.

Insights into the cut edge corrosion of 55% Al–Zn metal coating on steel from simultaneous electrochemical polarization and localised pH sensing experiments

Band microelectrode arrays were used to model the cut edge corrosion behaviour of 55% Al–Zn (Galvalume/Zincalume) and Zn coated steels in chloride and sulfate electrolytes. Simultaneous electrochemical polarization experiments revealed increased cathodic current on the steel during anodic dissolution of neighbouring Al–Zn alloy electrodes. The increased cathodic current on the steel was shown to be a result of pH buffering by Al3+, enhancing the rate of hydrogen evolution. A large negative shift of the corrosion potential of the Al–Zn alloy electrodes was observed during cathodic polarization on neighbouring steel electrodes and was attributed to alkaline pH generated from cathodic processes.

Anomalous Threshold Voltage Shift and Surface Passivation of Transparent Indium–Zinc–Oxide Electric-Double-Layer TFTs

Threshold voltage ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) instability and surface passivation effect of transparent indium-zinc-oxide electric-double-layer thin-film transistors (TFTs) are investigated. Unpassivated devices show a large negative threshold voltage shift of 0.68 V in the beginning of light-illuminated negative gate bias stress. Under longer time stress, anomalous positive <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> shifts are observed for both unpassivated and passivated TFTs, which is due to the mobile ions drifting in the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based solid-electrolyte gate dielectric. After surface passivation, the devices show neglectable negative <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> shifts of less than 0.1 V due to the protection of channel against the photodesorption of adsorbed oxygen ions.

Large negative lateral shifts due to negative refraction

When a thin structure in which negative refraction occurs (a metallo-dielectric structure or a photonic crystal) is illuminated by a beam, the reflected and transmitted beam can undergo a large negative lateral shift. This phenomenon can be seen as an interferential enhancement of the geometrical shift and can be considered a signature of negative refraction.

Function of Interfacial Dipole Monolayer in Organic Field Effect Transistors

The effect of interfacial dipole monolayer on carrier injection property of pentacene OFET was studied to understand the origin of contact resistance, which was evaluated from a modified transmission line model. The results showed the contact resistance of pentacene OFET with the dipole monolayer is much higher. This large discrepancy was found due to a small potential drop difference at the interface generated by the dipole monolayer. In addition, the strong local electric field confirmed the reason for the large negative threshold voltage shift. These studies show the importance of local electric field at pentacene–SiO2 interface generated by the dipole monolayer.

Effect of high-pressure oxygen annealing on negative bias illumination stress-induced instability of InGaZnO thin film transistors

Negative-bias illumination stress (NBIS) of amorphous InGaZnO (IGZO) transistors can cause a large negative shift (&amp;gt;7.1 V) in threshold voltage, something frequently attributed to the trapping of photoinduced hole carriers. This work demonstrates that the deterioration of threshold voltage by NBIS can be strongly suppressed by high-pressure annealing under 10 atm O2 ambient. This improvement occurred through a reduction in oxygen vacancy defects in the IGZO film, indicating that a photoinduced transition from VO to VO2+ was responsible for the NBIS-induced instability.

Large positive and negative lateral shifts near pseudo-Brewster dip on reflection from a chiral metamaterial slab

The lateral shifts from a slab of lossy chiral metamaterial are predicted for both perpendicular and parallel components of the reflected field, when the transverse electric (TE)-polarized incident wave is applied. By introducing different chirality parameter, the lateral shifts can be large positive or negative near the pseudo-Brewster angle. It is found that the lateral shifts from the negative chiral slab are affected by the angle of incidence and the chirality parameter. In the presence of inevitable loss of the chiral slab, the enhanced lateral shifts will be decreased, and the pseudo-Brewster angle will disappear correspondingly. For the negative chiral slab with loss which is invisible for the right circularly polarized (RCP) wave, we find that the loss of the chiral slab will lead to the fluctuation of the lateral shift with respect to the thickness of the chiral slab.The validity of the stationary-phase analysis is demonstrated by numerical simulations of a Gaussian-shaped beam.

Large positive and negative lateral optical beam shift due to long-range surface plasmon resonance

In this paper, we examine theoretically the beam shift at visible wavelengths on a long-range surface plasmon (LRSP) configuration by using the stationary-phase approach. We report that the lateral beam shift at the resonance of LRSP can be two orders of magnitude greater than a wavelength. It is also found that the sign of the lateral beam shift depends on the magnitude of the intrinsic damping relative to that of the radiative damping. Negative lateral beam shift occurs when the former is larger than the latter.

Anomalous H/D Isotope Effect on 35Cl NQR Frequencies and H/D Isotope Effect on 1H MAS NMR Spectra in Pyrrolidinium p-Chlorobenzoate

Abstract An anomalous isotope effect was observed in the 35Cl NQR frequency of pyrrolidinium p-chlorobenzoate (C4H8NH2+·ClC6H4COO−) by deuterium substitution of hydrogen atoms which form two kinds of N–H···O type hydrogen bonds. Large negative frequency shifts of the 35Cl resonance lines, reaching 309 kHz at 77 K and 267 kHz at 293 K, were obtained upon deuteration, although the Cl atom in the molecule formed no hydrogen bonds in the crystal. 1H MAS NMR lines showed significant changes by the deuterium substitution, while in contrast, small shifts of 13C CP/MAS NMR signals were obtained. Our measurements of 1H NMR spin–lattice relaxation times (T1) suggested that the H/D isotope shifts detected from the 35Cl NQR frequencies and 1H NMR spectra are due to structural changes rather than molecular dynamics. Single-crystal X-ray diffraction measurements showed two remarkable H/D isotope differences in the molecular arrangements, (i) the N–H length along the crystallographic a axis became 1 pm shorter, and (ii) the dihedral angle between benzene and the pyrrolidine ring changed by 1.1(2)° upon deuteration. Using density functional theory estimations, the anomalous 35Cl NQR frequency shifts and 1H MAS NMR line-shape changes could be explained by the dihedral angle change rather than the N–H length difference.

LRRC26 auxiliary protein allows BK channel activation at resting voltage without calcium

Large-conductance, voltage- and calcium-activated potassium (BK, or K(Ca)1.1) channels are ubiquitously expressed in electrically excitable and non-excitable cells, either as alpha-subunit (BKalpha) tetramers or together with tissue specific auxiliary beta-subunits (beta1-beta4). Activation of BK channels typically requires coincident membrane depolarization and elevation in free cytosolic Ca(2+) concentration ([Ca(2+)](i)), which are not physiological conditions for most non-excitable cells. Here we present evidence that in non-excitable LNCaP prostate cancer cells, BK channels can be activated at negative voltages without rises in [Ca(2+)](i) through their complex with an auxiliary protein, leucine-rich repeat (LRR)-containing protein 26 (LRRC26). LRRC26 modulates the gating of a BK channel by enhancing the allosteric coupling between voltage-sensor activation and the channel's closed-open transition. This finding reveals a novel auxiliary protein of a voltage-gated ion channel that gives an unprecedentedly large negative shift ( approximately -140 mV) in voltage dependence and provides a molecular basis for activation of BK channels at physiological voltages and calcium levels in non-excitable cells.