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p-Type and n-type quaterthiophene based semiconductors for thin film transistors operating in air?
C. Videlot-Ackermann,J. Zhang,J. Ackermann,H. Brisset,Y. Didane,P. Raynal,A. El Kassmi,F. Fages 한국물리학회 2009 Current Applied Physics Vol.9 No.1
The solution and solid-state properties as well as the organic thin film transistor (OTFT) behavior of α,ω-perfluorohexyl-quaterthiophene (DFH-4T) are presented and compared to those of quaterthiophene (4T) and α,ω-hexyl-quaterthiophene (DH-4T). UV/visible and fluorescence data showed the same weak effect of hexyl and perfluorohexyl substitutions on the optical properties of 4T core. Growth mechanism of DFH-4T based thin films deposited by vacuum deposition on heated Si/SiO2 substrates has been investigated in details and demonstrated to be identical to that of DH-4T. The characterization in air of the charge transport properties of thin films based on DH- 4T and DFH-4T revealed a switch from p- to n-type, respectively, depending on the nature of alkyl chains. A qualitative Schottky-type charge injection barrier model, based on HOMO and LUMO energy levels estimated from cyclic voltammograms and optical absorption spectra of DFH-4T relative to those of 4T and DH-4T, was introduced to explain such change in semiconducting properties observed under ambient conditions (temperature, light, air). In an attempt to answer to the question of ‘‘are p-type and n-type quaterthiophene derivatives appropriate semiconductors for thin film transistors operating in air?” we investigated the influence of the nature of the dielectrics to obtain OTFTs operating in air and showing environmentally stable mobility. The solution and solid-state properties as well as the organic thin film transistor (OTFT) behavior of α,ω-perfluorohexyl-quaterthiophene (DFH-4T) are presented and compared to those of quaterthiophene (4T) and α,ω-hexyl-quaterthiophene (DH-4T). UV/visible and fluorescence data showed the same weak effect of hexyl and perfluorohexyl substitutions on the optical properties of 4T core. Growth mechanism of DFH-4T based thin films deposited by vacuum deposition on heated Si/SiO2 substrates has been investigated in details and demonstrated to be identical to that of DH-4T. The characterization in air of the charge transport properties of thin films based on DH- 4T and DFH-4T revealed a switch from p- to n-type, respectively, depending on the nature of alkyl chains. A qualitative Schottky-type charge injection barrier model, based on HOMO and LUMO energy levels estimated from cyclic voltammograms and optical absorption spectra of DFH-4T relative to those of 4T and DH-4T, was introduced to explain such change in semiconducting properties observed under ambient conditions (temperature, light, air). In an attempt to answer to the question of ‘‘are p-type and n-type quaterthiophene derivatives appropriate semiconductors for thin film transistors operating in air?” we investigated the influence of the nature of the dielectrics to obtain OTFTs operating in air and showing environmentally stable mobility.
Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert
Aartsen, Mark,Ackermann, Markus,Adams, Jenni,Aguilar, Juan Antonio,Ahlers, Markus,Ahrens, Maryon,Al Samarai, Imen,Altmann, David,Andeen, Karen,Anderson, Tyler,Ansseau, Isabelle,Anton, Gisela,Arguelles American Association for the Advancement of Scienc 2018 Science Vol.361 No.6398
<P><B>Neutrino emission from a flaring blazar</B></P><P>Neutrinos interact only very weakly with matter, but giant detectors have succeeded in detecting small numbers of astrophysical neutrinos. Aside from a diffuse background, only two individual sources have been identified: the Sun and a nearby supernova in 1987. A multiteam collaboration detected a high-energy neutrino event whose arrival direction was consistent with a known blazar—a type of quasar with a relativistic jet oriented directly along our line of sight. The blazar, TXS 0506+056, was found to be undergoing a gamma-ray flare, prompting an extensive multiwavelength campaign. Motivated by this discovery, the IceCube collaboration examined lower-energy neutrinos detected over the previous several years, finding an excess emission at the location of the blazar. Thus, blazars are a source of astrophysical neutrinos.</P><P><I>Science</I>, this issue p. 147, p. eaat1378</P><P>A high-energy neutrino event detected by IceCube on 22 September 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056. Prompted by this association, we investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We found an excess of high-energy neutrino events, with respect to atmospheric backgrounds, at that position between September 2014 and March 2015. Allowing for time-variable flux, this constitutes 3.5σ evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 flaring episode. This suggests that blazars are identifiable sources of the high-energy astrophysical neutrino flux.</P>
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
Aartsen, Mark,Ackermann, Markus,Adams, Jenni,Aguilar, Juan Antonio,Ahlers, Markus,Ahrens, Maryon,Al Samarai, Imen,Altmann, David,Andeen, Karen,Anderson, Tyler,Ansseau, Isabelle,Anton, Gisela,Argü American Association for the Advancement of Scienc 2018 Science Vol.361 No.6398
<P>Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.</P>
Search for annihilating dark matter in the Sun with 3 years of IceCube data : IceCube Collaboration
Aartsen, M. G.,Ackermann, M.,Adams, J.,Aguilar, J. A.,Ahlers, M.,Ahrens, M.,Altmann, D.,Andeen, K.,Anderson, T.,Ansseau, I.,Anton, G.,Archinger, M.,Argü,elles, C.,Auffenberg, J.,Axani, S.,Bai, X. Springer-Verlag 2017 The European physical journal. C, Particles and fi Vol.77 No.3
Measurement of atmospheric tau neutrino appearance with IceCube DeepCore
Aartsen, M. G.,Ackermann, M.,Adams, J.,Aguilar, J. A.,Ahlers, M.,Ahrens, M.,Altmann, D.,Andeen, K.,Anderson, T.,Ansseau, I.,Anton, G.,Argü,elles, C.,Auffenberg, J.,Axani, S.,Backes, P.,Bagherpour, American Physical Society 2019 Physical review. D Vol.99 No.3
Search for sterile neutrino mixing using three years of IceCube DeepCore data
Aartsen, M. G.,Ackermann, M.,Adams, J.,Aguilar, J. A.,Ahlers, M.,Ahrens, M.,Al Samarai, I.,Altmann, D.,Andeen, K.,Anderson, T.,Ansseau, I.,Anton, G.,Archinger, M.,Argü,elles, C.,Auffenberg, J.,Axa American Physical Society 2017 Physical review. D Vol.95 No.11
<P>We present a search for a light sterile neutrino using three years of atmospheric neutrino data from the DeepCore detector in the energy range of approximately 10-60 GeV. DeepCore is the low-energy subarray of the IceCube Neutrino Observatory. The standard three-neutrino paradigm can be probed by adding an additional light (Delta m(41)(2) similar to 1 eV(2)) sterile neutrino. Sterile neutrinos do not interact through the standard weak interaction and, therefore, cannot be directly detected. However, their mixing with the three active neutrino states leaves an imprint on the standard atmospheric neutrino oscillations for energies below 100 GeV. A search for such mixing via muon neutrino disappearance is presented here. The data are found to be consistent with the standard three-neutrino hypothesis. Therefore, we derive limits on the mixing matrix elements at the level of vertical bar U mu(4)vertical bar(2) < 0.11 and vertical bar U-tau 4 vertical bar(2) < 0.15 (90% C. L.) for the sterile neutrino mass splitting Delta m(41)(2) = 1.0 eV(2).</P>
Search for neutrinos from decaying dark matter with IceCube : IceCube Collaboration
Aartsen, M. G.,Ackermann, M.,Adams, J.,Aguilar, J. A.,Ahlers, M.,Ahrens, M.,Samarai, I. Al,Altmann, D.,Andeen, K.,Anderson, T.,Ansseau, I.,Anton, G.,Argü,elles, C.,Auffenberg, J.,Axani, S.,Backes, Springer Berlin Heidelberg 2018 European Physical Journal C Vol.78 No.10
<P>With the observation of high-energy astrophysical neutrinos by the IceCube Neutrino Observatory, interest has risen in models of PeV-mass decaying dark matter particles to explain the observed flux. We present two dedicated experimental analyses to test this hypothesis. One analysis uses 6 years of IceCube data focusing on muon neutrino ‘track’ events from the Northern Hemisphere, while the second analysis uses 2 years of ‘cascade’ events from the full sky. Known background components and the hypothetical flux from unstable dark matter are fitted to the experimental data. Since no significant excess is observed in either analysis, lower limits on the lifetime of dark matter particles are derived: we obtain the strongest constraint to date, excluding lifetimes shorter than [FORMULA OMISSION] at 90% CL for dark matter masses above [FORMULA OMISSION].</P>