Polarity control of carrier injection at ferroelectric/metal interfaces for electrically switchable diode and photovoltaic effects

We investigated a switchable ferroelectric diode effect and its physical mechanism in Pt/BiFeO3/SrRuO3 thin-film capacitors. Our results of electrical measurements support that, near the Pt/BiFeO3 interface of as-grown samples, a defective layer (possibly, an oxygen-vacancy-rich layer) becomes formed and disturbs carrier injection. We therefore used an electrical training process to obtain ferroelectric control of the diode polarity where, by changing the polarization direction using an external bias, we could switch the transport characteristics between forward and reverse diodes. Our system is characterized with a rectangular polarization hysteresis loop, with which we confirmed that the diode polarity switching occurred at the ferroelectric coercive voltage. Moreover, we observed a simultaneous switching of the diode polarity and the associated photovoltaic response dependent on the ferroelectric domain configurations. Our detailed study suggests that the polarization charge can affect the Schottky barrier at the ferroelectric/metal interfaces, resulting in a modulation of the interfacial carrier injection. The amount of polarization-modulated carrier injection can affect the transition voltage value at which a space-charge-limited bulk current-voltage (J-V) behavior is changed from Ohmic (i.e., J ~ V) to nonlinear (i.e., J ~ V^n with n \geq 2). This combination of bulk conduction and polarization-modulated carrier injection explains the detailed physical mechanism underlying the switchable diode effect in ferroelectric capacitors.Comment: Accepted for publication in Phys. Rev.

Non-Fermi liquid behavior and scaling of low frequency suppression in optical conductivity spectra of CaRuO3_3

Optical conductivity spectra $\sigma_1(\omega)$ of paramagnetic CaRuO$_3$ are investigated at various temperatures. At T=10 K, it shows a non-Fermi liquid behavior of $\sigma_1(\omega)\sim 1/{\omega}^{\frac 12}$, similar to the case of a ferromagnet SrRuO$_3$. As the temperature ($T$) is increased, on the other hand, $\sigma_1(\omega)$ in the low frequency region is progressively suppressed, deviating from the 1/{\omega}^{\frac 12%}-dependence. Interestingly, the suppression of $\sigma_1(\omega)$ is found to scale with $\omega /T$ at all temperatures. The origin of the $$ scaling behavior coupled with the non-Fermi liquid behavior is discussed.Comment: 4 pages, 3 figure

Scaling of the anomalous Hall effect in Sr1−x_{1-x}Cax_xRuO3_3

The anomalous Hall effect (AHE) of ferromagnetic thin films of Sr$_{1-x}$Ca$_{x}$RuO$_3$ (0 $\leq x \leq$ 0.4) is studied as a function of $x$ and temperature $T$. As $x$ increases, both the transition temperature $T_c$ and the magnetization $M$ are reduced and vanish near $x \sim$ 0.7. For all compositions, the transverse resistivity $\rho_{H}$ varies non-monotonously with $T$, and even changes sign, thus violating the conventional expression $\rho_{H}=R_o B + 4\pi R_s M(T)$ ($B$ is the magnetic induction, while $R_o$ and $R_s$ are the ordinary and anomalous Hall coefficients). From the rather complicated data of $\rho_H$, we find a scaling behavior of the transverse conductivity $\sigma_{xy}$ with $M(T)$, which is well reproduced by the first-principles band calculation assuming the intrinsic origin of the AHE.Comment: REVTeX 4 style; 5 pages, 3 figures; revised 23/2 and accepted for publicatio

The impact of near-term climate policy choices on technology and emission transition pathways

This paper explores the implications of delays (to 2030) in implementing optimal policies for long-term transition pathways to limit climate forcing to 450 ppm CO2e on the basis of the AMPERE Work Package 2 model comparison study. The paper highlights the critical importance of the period 2030-2050 for ambitious mitigation strategies. In this period, the most rapid shift to low greenhouse gas emitting technology occurs. In the delayed response emission mitigation scenarios, an even faster transition rate in this period is required to compensate for the additional emissions before 2030. Our physical deployment measures indicate that the availability of CCS technology could play a critical role in facilitating the attainment of ambitious mitigation goals. Without CCS, deployment of other mitigation technologies would become extremely high in the 2030-2050 period. Yet the presence of CCS greatly alleviates the challenges to the transition particularly after the delayed climate policies, lowering the risk that the long-term goal becomes unattainable. The results also highlight the important role of bioenergy with CO2 capture and storage (BECCS), which facilitates energy production with negative carbon emissions. If BECCS is available, transition pathways exceed the emission budget in the mid-term, removing the excess with BECCS in the long term. Excluding either BE or CCS from the technology portfolio implies that emission reductions need to take place much earlier

Metabolic control of tobacco pollination by sugars and invertases

Pollination in flowering plants is initiated by germination of pollen grains on stigmas followed by fast growth of pollen tubes representing highly energy-consuming processes. The symplastic isolation of pollen grains and tubes requires import of Suc available in the apoplast. We show that the functional coupling of Suc cleavage by invertases and uptake of the released hexoses by monosaccharide transporters are critical for pollination in tobacco (Nicotiana tabacum). Transcript profiling, in situ hybridization, and immunolocalization of extracellular invertases and two monosaccharide transporters in vitro and in vivo support the functional coupling in supplying carbohydrates for pollen germination and tube growth evidenced by spatiotemporally coordinated expression. Detection of vacuolar invertases in maternal tissues by these approaches revealed metabolic cross talk between male and female tissues and supported the requirement for carbohydrate supply in transmitting tissue during pollination. Tissue-specific expression of an invertase inhibitor and addition of the chemical invertase inhibitor miglitol strongly reduced extracellular invertase activity and impaired pollen germination. Measurements of (competitive) uptake of labeled sugars identified two import pathways for exogenously available Suc into the germinating pollen operating in parallel: direct Suc uptake and via the hexoses after cleavage by extracellular invertase. Reduction of extracellular invertase activity in pollen decreases Suc uptake and severely compromises pollen germination. We further demonstrate that Glc as sole carbon source is sufficient for pollen germination, whereas Suc is supporting tube growth, revealing an important regulatory role of both the invertase substrate and products contributing to a potential metabolic and signaling-based multilayer regulation of pollination by carbohydrates.Peer Reviewe

Magnetotransport in manganite trilayer junctions grown by 90° off-axis sputtering

We report magnetotransport studies on La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3 trilayer junctions, fabricated using 90° off-axis sputtering. Films were grown on both (001) (LaAlO3)0.3–(Sr2AlTaO6)0.7(LaAlO3)0.3–(Sr2AlTaO6)0.7 and (110) NdGaO3NdGaO3 substrates. The sputtered trilayers show improved junction resistance uniformity over those made using pulsed laser deposition. Cross-sectional transmission electron microscopy and atomic force microscopy studies confirm smooth interfaces and a uniform barrier. Magnetoresistances up to ∼100% are observed for junctions on (001) (LaAlO3)0.3–(Sr2AlTaO6)0.7(LaAlO3)0.3–(Sr2AlTaO6)0.7 with a 30 Å barrier at 13 K and around 100 Oe. Junction magnetoresistance versus magnetic field behavior is more stable, indicating improved transport and magnetic homogeneity across the junction. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70148/2/APPLAB-79-2-233-1.pd

Автоматизация создания перехватчиков событий в системе управления проектами Team Foundation Server с помощью Rest API для Visual Studio Team Services и Team Foundation Server

В данной статье рассмотрен метод автоматизации процесса создания перехватчиков событий для проектов в системе управления проектами Team Foundation Server с помощью REST API для Visual Studio Team Services и Team Foundation Server. В качестве примера рассмотрено создание перехватчика событий для проектов, работающий с системами контроля версий TFVC. This article describes the method of automation of the service hook setting process for projects in the Project Management System Team Foundation Server using the REST API for Visual Studio Team Services and Team Foundation Server. By way of example, the creation of the service hook for projects operating with TFVC version control systems is considered

Phase Dependent Thermopower in Andreev Interferometers

We report measurements of the thermopower S of mesoscopic Andreev interferometers, which are hybrid loops with one arm fabricated from a superconductor (Al), and one arm from a normal metal (Au). S depends on the phase of electrons in the interferometer, oscillating as a function of magnetic flux with a period of one flux quantum (= h/2e). The magnitude of S increases as the temperature T is lowered, reaching a maximum around T = 0.14 K, and decreases at lower temperatures. The symmetry of S oscillations with respect to magnetic flux depends on the topology of the sample.Comment: 4 pages, 4 figure