Search results for "Ambipolar diffusion"
showing 10 items of 22 documents
Injected 1+ ion beam as a diagnostics tool of charge breeder ECR ion source plasmas
2015
International audience; Charge breeder electron cyclotron resonance ion sources (CB-ECRIS) are used as 1+ →n+ charge multiplication devices of post-accelerated radioactive ion beams. The charge breeding process involves thermalization of the injected 1+ ions with the plasma ions in ion–ion collisions, subsequent ionization by electron impact and extraction of the n+ ions. Charge breeding experiments of 85Rb and 133Cs ion beams with the 14.5 GHz PHOENIX CB-ECRIS operating with oxygen gas demonstrate the plasma diagnostics capabilities of the 1+ injection method. Two populations can be distinguished in the m/q-spectrum of the extracted ion beams, the low (1+ and 2+) charge states repres…
Electrochemical polymerization of ambipolar carbonyl-functionalized indenofluorene with memristive properties
2019
Abstract Carbonyl-functionalized indenofluorene was electropolymerized with a high faradaic efficiency of 85% and the solid state properties of the resulting polymeric thin films were investigated. They displayed modular optical properties depending on their oxidation state. The approach used for inorganic semiconductors was applied to polyindeonofluorene derivative. Mott-Schottky analysis evidenced a switching from p-type to n-type electrical conduction, suggesting an ambipolar behaviour of the polymer. As an application, flexible organic memristors were fabricated and resistive switching properties were observed.
Unravelling substitution effects on charge transfer characteristics in cocrystals of pyrene based donors and 3,5-dinitrobenzoic acid
2019
Here we report charge-transfer cocrystals composed of pyrene and amino/bromopyrene as π-donors (D) and 3,5-dinitrobenzoic acid (A) as a π-acceptor. The 1 : 1 cocrystals of pyrene/1-aminopyrene adopt a ⋯DADADA⋯ mixed stack arrangement whereas the 2 : 1 cocrystal of 1-bromopyrene and 3,5-dinitrobenzoic acid shows ⋯DDADDA⋯ stacking. Crystallographic, spectral and theoretical studies reveal that the frontier molecular orbital energy level rather than the π-donor strength plays the governing role in predicting charge transfer. In addition, a theoretical study demonstrates that the ambipolar semiconductor nature in cocrystals of the pyrene/aminopyrene donor and the p-type nature of bromopyrene wi…
H-2, H-3(+) and the age of molecular clouds and prestellar cores
2012
Measuring the age of molecular clouds and prestellar cores is a difficult task that has not yet been successfully accomplished although the information is of paramount importance to help in understanding and discriminating between different formation scenarios. Most chemical clocks suffer from unknown initial conditions and are therefore difficult to use. We propose a new approach based on a subset of deuterium chemistry that takes place in the gas phase and for which initial conditions are relatively well known. It relies primarily on the conversion of H 3 + into H 2D + to initiate deuterium enrichment of the molecular gas. This conversion is controlled by the ortho/para ratio of H2 that i…
Tuning Of Organic Heterojunction Conductivity By The Substituents' Electronic Effects In Phthalocyanines For Ambipolar Gas Sensors
2021
Abstract Exploiting organic heterojunction effects in electrical devices are an important strategy to improve the electrical conductivity, which can be utilized into improving the conductometric gas sensors performances. In this endeavor, the present article reports fabrication of organic heterostructures in a bilayer device configuration incorporating octa-substituted nickel phthalocyanines (NiPc) and radical lutetium bis-phthalocyanine (LuPc2) and investigates their sensing properties towards NH3 vapor. NiPc having hexyl sulfanyl, hexyl sulfonyl and p-carboxyphenoxy moieties are synthesized, which electronic effects are electron donating, accepting and moderate accepting, respectively, al…
Acoustic manipulation of electron-hole pairs in GaAs at room temperature
2004
We demonstrate the optically detected long-range (>100 μm) ambipolar transport of photogenerated electrons and holes at room temperature by surface acoustic waves (SAWs) in (In,Ga)As-based quantum well structures coupled to an optical microcavity. We also show the control of the propagation direction of the carriers by a switch composed of orthogonal SAW beams, which can be used as a basic control gate for information processing based on ambipolar transport.
Two-Step Solution-Processed Two-Component Bilayer Phthalocyaninato Copper-Based Heterojunctions with Interesting Ambipolar Organic Transiting and Eth…
2016
International audience; The two-component phthalocyaninato copper-based heterojunctions fabricated from n-type CuPc(COOC8H17)(8) and p-type CuPc(OC8H17)(8) by a facile two-step solution-processing quasi-Langmuir-Shafer method with both n/p- and p/n-bilayer structures are revealed to exhibit typical ambipolar air-stable organic thin-film transistor (OTFT) performance. The p/n-bilayer devices constructed by depositing CuPc(COOC8H17)(8) film on CuPc(OC8H17)(8) sub-layer show superior OTFT performance with hole and electron mobility of 0.11 and 0.02 cm(2) V-1 s(-1), respectively, over the ones with n/p-bilayer heterojunction structure with the hole and electron mobility of 0.03 and 0.016 cm(2) …
On the interest of ambipolar materials for gas sensing
2017
International audience; Based on the electrochemical properties of a series of metallophthalocyanines this article shows that the phthalocyanine bearing four alkoxy groups and twelve fluorine atoms behaves approximately as those with eight fluorine atoms. This indicates that the electron-donating effect of one alkoxy group balances the electro-withdrawing effect of one fluorine atom. We engaged three metallophthalocyanines, namely the octafluoro copper phthalocyanine, Cu(F8Pc), an octaester metallophthalocyanine and a phthalocyanine bearing four alkoxy groups and twelve fluorine atoms, Zn(T4F12Pc), in building original conductometric transducers that are Molecular Semiconductor – Doped Insu…
Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE
2016
A family of new branched phosphine derivatives {Ph2N-(C6H4)n-}3P → E (E = O 1-3, n = 1-3; E = S 4-6, n = 1-3; E = Se 7-9, n = 1-3; E = AuC6F5 4-6, n = 1-3), which are the donor-acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λem = 403-483 nm in CH2Cl2 solution, λem = 400-469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge -(C6H4)n-. The pyramidal geometry of central R3P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer form…
Magnetic Properties of Quinoidal Oligothiophenes: More Than Good Candidates for Ambipolar Organic Semiconductors?
2006
A series of quinoidal oligothiophenes have been investigated by means of solid-state Fourier-transform (FT)-Raman and electron spin resonance (ESR) spectroscopies complemented with density functional theory calculations. FT-Raman spectra recorded as a function of temperature show that, upon laser irradiation, the molecules undergo a reversible structural evolution from a quinoid-type pattern at low temperature to an aromatic-type pattern at high temperature. Moreover, ESR spectra show that a portion of these compounds exists in a biradical state at room temperature. These seemingly disconnected findings and others, such as conformational isomerism, are consistently explained by the consider…