577 research outputs found
Frequency shifts of photoassociative spectra of ultracold metastable Helium atoms : a new measurement of the s-wave scattering length
We observe light-induced frequency shifts in one-color photoassociative
spectra of magnetically trapped He atoms in the metastable
state. A pair of ultracold spin-polarized helium atoms is excited into
a molecular bound state in the purely long range potential connected to
the asymptote. The shift arises from the optical coupling of
the molecular excited bound state with the scattering states and the bound
states of two colliding atoms. We measure the frequency-shifts for
several ro-vibrational levels in the potential and find a linear
dependence on the photoassociation laser intensity. Comparison with a
theoretical analysis provides a good indication for the s-wave scattering
length of the quintet () potential, nm, which
is significantly lower than most previous results obtained by non-spectroscopic
methods.Comment: 7 pages, 4 figure
Accurate determination of the scattering length of metastable Helium atoms using dark resonances between atoms and exotic molecules
We present a new measurement of the s-wave scattering length a of
spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon
photoassociation spectroscopy and dark resonances we measure the energy
E_{v=14}= -91.35 +/- 0.06 MHz of the least bound state v=14 in the interaction
potential of the two atoms. We deduce a value of a = 7.512 +/- 0.005 nm, which
is at least one hundred times more precise than the best previous
determinations and is in disagreement with some of them. This experiment also
demonstrates the possibility to create exotic molecules binding two metastable
atoms with a lifetime of the order of 1 microsecond.Comment: 4 pages, 4 figure
Influence of Thermal Treatment on The Electronic Properties of ITO Thin Films Obtained by RF Cathodic Pulverization. Study of Solar Cells Based on Silicon/(RF Sputtered) ITO Junctions
ITO (Indium Tin Oxide) thin films obtained by R.F cathodic sputtering have been studied. The influence
of thermal treatment on the electronic properties of the films has been particularly investigated. Electrical
measurements were performed between 95 and 600 K. Free carriers concentration in the film were
measured by Hall effect coefficient. Optical indices were determined by computer drawing of charts
allowing to simplify Manifacier method
Carrier drift velocity and edge magnetoplasmons in graphene
We investigate electron dynamics at the graphene edge by studying the
propagation of collective edge magnetoplasmon (EMP) excitations. By timing the
travel of narrow wave-packets on picosecond time scales around exfoliated
samples, we find chiral propagation with low attenuation at a velocity which is
quantized on Hall plateaus. We extract the carrier drift contribution from the
EMP propagation and find it to be slightly less than the Fermi velocity, as
expected for an abrupt edge. We also extract the characteristic length for
Coulomb interaction at the edge and find it to be smaller than for soft,
depletion edge systems.Comment: 5 pages, 3 figures of main text and 6 pages, 6 figures of
supplemental materia
Resistive switching and charge transport mechanisms in ITO/ZnO/p-Si devices
[EN] The resistive switching properties of ITO/ZnO/p-Si devices have been studied, which present well-defined resistance states with more than five orders of magnitude difference in current. Both the high resistance state (HRS) and the low resistance state (LRS) were induced by either sweeping or pulsing the voltage, observing some differences in the HRS. Finally, the charge transport mechanisms dominating the pristine, HRS, and LRS states have been analyzed in depth, and the obtained structural parameters suggest a partial re-oxidation of the conductive nanofilaments and a reduction of the effective conductive area.This work was financially supported by the Spanish Ministry of Economy and Competitiveness (Project Nos. TEC2012-38540-C02-01 and TEC2016-76849-C2-1-R). O.B. also acknowledges the subprogram "Ayudas para Contratos Predoctorales para la Formacion de Doctores" of the Spanish Ministry of Economy and Competitiveness for economical support. X.P., C.L., and C.G. are grateful to C. Frilay for his expertise in the maintenance of the sputtering kit used for the growth of the ZnO films.Blázquez, O.; Frieiro, J.; López-Vidrier, J.; Guillaume, C.; Portier, X.; Labbé, C.; Sanchis Kilders, P.... (2018). Resistive switching and charge transport mechanisms in ITO/ZnO/p-Si devices. Applied Physics Letters. 113(18):1-6. https://doi.org/10.1063/1.50469111611318I. G. Baek , M. S. Lee , S. Sco , M. J. Lee , D. H. Seo , D.S. Suh , J. C. Park , S. O. Park , H. S. Kim , I. K. Yoo , U.I. Chung , and J. T. Moon , in IEDM Technical Digest. IEEE International Electron Devices Meeting, 2004 ( IEEE, 2004), pp. 587–590.Waser, R., & Aono, M. (2007). Nanoionics-based resistive switching memories. Nature Materials, 6(11), 833-840. doi:10.1038/nmat2023Kaeriyama, S., Sakamoto, T., Sunamura, H., Mizuno, M., Kawaura, H., Hasegawa, T., … Aono, M. (2005). A nonvolatile programmable solid-electrolyte nanometer switch. 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Nanoscale Memristor Device as Synapse in Neuromorphic Systems. Nano Letters, 10(4), 1297-1301. doi:10.1021/nl904092hVescio, G., Crespo-Yepes, A., Alonso, D., Claramunt, S., Porti, M., Rodriguez, R., … Aymerich, X. (2017). Inkjet Printed HfO2-Based ReRAMs: First Demonstration and Performance Characterization. IEEE Electron Device Letters, 38(4), 457-460. doi:10.1109/led.2017.2668599Valov, I. (2013). Redox-Based Resistive Switching Memories (ReRAMs): Electrochemical Systems at the Atomic Scale. ChemElectroChem, 1(1), 26-36. doi:10.1002/celc.201300165Martín, G., González, M. B., Campabadal, F., Peiró, F., Cornet, A., & Estradé, S. (2017). Transmission electron microscopy assessment of conductive-filament formation in Ni–HfO2–Si resistive-switching operational devices. Applied Physics Express, 11(1), 014101. doi:10.7567/apex.11.014101Simanjuntak, F. M., Panda, D., Wei, K.-H., & Tseng, T.-Y. (2016). Status and Prospects of ZnO-Based Resistive Switching Memory Devices. Nanoscale Research Letters, 11(1). doi:10.1186/s11671-016-1570-yKim, J., & Yong, K. (2011). Mechanism Study of ZnO Nanorod-Bundle Sensors for H2S Gas Sensing. The Journal of Physical Chemistry C, 115(15), 7218-7224. doi:10.1021/jp110129fYuan, Q., Zhao, Y.-P., Li, L., & Wang, T. (2009). Ab Initio Study of ZnO-Based Gas-Sensing Mechanisms: Surface Reconstruction and Charge Transfer. The Journal of Physical Chemistry C, 113(15), 6107-6113. doi:10.1021/jp810161jSeo, J. W., Park, J.-W., Lim, K. S., Yang, J.-H., & Kang, S. J. (2008). Transparent resistive random access memory and its characteristics for nonvolatile resistive switching. Applied Physics Letters, 93(22), 223505. doi:10.1063/1.3041643Rahaman, S. Z., Maikap, S., Chiu, H.-C., Lin, C.-H., Wu, T.-Y., Chen, Y.-S., … Tsai, M.-J. (2010). Bipolar Resistive Switching Memory Using Cu Metallic Filament in Ge[sub 0.4]Se[sub 0.6] Solid Electrolyte. Electrochemical and Solid-State Letters, 13(5), H159. doi:10.1149/1.3339449Simanjuntak, F. M., Panda, D., Tsai, T.-L., Lin, C.-A., Wei, K.-H., & Tseng, T.-Y. (2015). Enhancing the memory window of AZO/ZnO/ITO transparent resistive switching devices by modulating the oxygen vacancy concentration of the top electrode. Journal of Materials Science, 50(21), 6961-6969. doi:10.1007/s10853-015-9247-ySimanjuntak, F. M., Prasad, O. K., Panda, D., Lin, C.-A., Tsai, T.-L., Wei, K.-H., & Tseng, T.-Y. (2016). Impacts of Co doping on ZnO transparent switching memory device characteristics. Applied Physics Letters, 108(18), 183506. doi:10.1063/1.4948598Simanjuntak, F. M., Panda, D., Tsai, T.-L., Lin, C.-A., Wei, K.-H., & Tseng, T.-Y. (2015). Enhanced switching uniformity in AZO/ZnO1−x/ITO transparent resistive memory devices by bipolar double forming. Applied Physics Letters, 107(3), 033505. doi:10.1063/1.4927284Liu, Q., Guan, W., Long, S., Jia, R., Liu, M., & Chen, J. (2008). Resistive switching memory effect of ZrO[sub 2] films with Zr[sup +] implanted. Applied Physics Letters, 92(1), 012117. doi:10.1063/1.2832660Shuai, Y., Zhou, S., Bürger, D., Helm, M., & Schmidt, H. (2011). Nonvolatile bipolar resistive switching in Au/BiFeO3/Pt. Journal of Applied Physics, 109(12), 124117. doi:10.1063/1.3601113Chen, J.-Y., Hsin, C.-L., Huang, C.-W., Chiu, C.-H., Huang, Y.-T., Lin, S.-J., … Chen, L.-J. (2013). Dynamic Evolution of Conducting Nanofilament in Resistive Switching Memories. Nano Letters, 13(8), 3671-3677. doi:10.1021/nl4015638Hubbard, W. A., Kerelsky, A., Jasmin, G., White, E. R., Lodico, J., Mecklenburg, M., & Regan, B. C. (2015). Nanofilament Formation and Regeneration During Cu/Al2O3 Resistive Memory Switching. Nano Letters, 15(6), 3983-3987. doi:10.1021/acs.nanolett.5b00901Liu, Q., Sun, J., Lv, H., Long, S., Yin, K., Wan, N., … Liu, M. (2012). Real-Time Observation on Dynamic Growth/Dissolution of Conductive Filaments in Oxide-Electrolyte-Based ReRAM. Advanced Materials, 24(14), 1844-1849. doi:10.1002/adma.201104104Zhu, X., Wu, H.-Z., Qiu, D.-J., Yuan, Z., Jin, G., Kong, J., & Shen, W. (2010). Photoluminescence and resonant Raman scattering in N-doped ZnO thin films. Optics Communications, 283(13), 2695-2699. doi:10.1016/j.optcom.2010.03.006Cerqueira, M. F., Vasilevskiy, M. I., Oliveira, F., Rolo, A. G., Viseu, T., Ayres de Campos, J., … Correia, R. (2011). Resonant Raman scattering in ZnO:Mn and ZnO:Mn:Al thin films grown by RF sputtering. Journal of Physics: Condensed Matter, 23(33), 334205. doi:10.1088/0953-8984/23/33/334205Marchewka, A., Roesgen, B., Skaja, K., Du, H., Jia, C.-L., Mayer, J., … Menzel, S. (2015). Nanoionic Resistive Switching Memories: On the Physical Nature of the Dynamic Reset Process. Advanced Electronic Materials, 2(1), 1500233. doi:10.1002/aelm.201500233Krzywiecki, M., Grządziel, L., Sarfraz, A., Iqbal, D., Szwajca, A., & Erbe, A. (2015). Zinc oxide as a defect-dominated material in thin films for photovoltaic applications – experimental determination of defect levels, quantification of composition, and construction of band diagram. Physical Chemistry Chemical Physics, 17(15), 10004-10013. doi:10.1039/c5cp00112aMurgatroyd, P. N. (1970). Theory of space-charge-limited current enhanced by Frenkel effect. Journal of Physics D: Applied Physics, 3(2), 151-156. doi:10.1088/0022-3727/3/2/308Electron emission in intense electric fields. (1928). Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 119(781), 173-181. doi:10.1098/rspa.1928.0091Özgür, Ü., Alivov, Y. I., Liu, C., Teke, A., Reshchikov, M. A., Doğan, S., … Morkoç, H. (2005). A comprehensive review of ZnO materials and devices. Journal of Applied Physics, 98(4), 041301. doi:10.1063/1.1992666Kaidashev, E. M., Lorenz, M., von Wenckstern, H., Rahm, A., Semmelhack, H.-C., Han, K.-H., … Grundmann, M. (2003). 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Characterization of the proneural gene regulatory network during mouse telencephalon development
BACKGROUND: The proneural proteins Mash1 and Ngn2 are key cell autonomous regulators of neurogenesis in the mammalian central nervous system, yet little is known about the molecular pathways regulated by these transcription factors. RESULTS: Here we identify the downstream effectors of proneural genes in the telencephalon using a genomic approach to analyze the transcriptome of mice that are either lacking or overexpressing proneural genes. Novel targets of Ngn2 and/or Mash1 were identified, such as members of the Notch and Wnt pathways, and proteins involved in adhesion and signal transduction. Next, we searched the non-coding sequence surrounding the predicted proneural downstream effector genes for evolutionarily conserved transcription factor binding sites associated with newly defined consensus binding sites for Ngn2 and Mash1. This allowed us to identify potential novel co-factors and co-regulators for proneural proteins, including Creb, Tcf/Lef, Pou-domain containing transcription factors, Sox9, and Mef2a. Finally, a gene regulatory network was delineated using a novel Bayesian-based algorithm that can incorporate information from diverse datasets. CONCLUSION: Together, these data shed light on the molecular pathways regulated by proneural genes and demonstrate that the integration of experimentation with bioinformatics can guide both hypothesis testing and hypothesis generation
Transformation kinetics of alloys under non-isothermal conditions
The overall solid-to-solid phase transformation kinetics under non-isothermal
conditions has been modeled by means of a differential equation method. The
method requires provisions for expressions of the fraction of the transformed
phase in equilibrium condition and the relaxation time for transition as
functions of temperature. The thermal history is an input to the model. We have
used the method to calculate the time/temperature variation of the volume
fraction of the favored phase in the alpha-to-beta transition in a zirconium
alloy under heating and cooling, in agreement with experimental results. We
also present a formulation that accounts for both additive and non-additive
phase transformation processes. Moreover, a method based on the concept of path
integral, which considers all the possible paths in thermal histories to reach
the final state, is suggested.Comment: 16 pages, 7 figures. To appear in Modelling Simul. Mater. Sci. En
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