Energy level alignment and injection barriers at spin injection contacts between La0.7Sr0.3MnO3 and organic semiconductors

Grobosch, M.; Dörr, K.; Gangineni, R. B.; Knupfer, M.

doi:10.1063/1.2829391

Cited by 23 publications

(23 citation statements)

References 45 publications

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“…Strong electrical dipoles are present at many OSC/metal interfaces and these interfacial dipoles can significantly alter the non-interacting equilibrium energy levels 11,13,14,[22][23][24][25][26][27][28] . Thus far, little is experimentally known about the role of these vacuum level shifts on spin injection and extraction.…”

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confidence: 99%

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

et al. 2010

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Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves 1 to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as another degree of freedom in semiconductor devices has been slower to take off. One future avenue that may expand the spintronic technology base is to take advantage of the flexibility intrinsic to organic semiconductors (OSCs), where it is possible to engineer and control their electronic properties and tailor them to obtain new device concepts 2 . Here we show that we can control the spin polarization of extracted charge carriers from an OSC by the inclusion of a thin interfacial layer of polar material. The electric dipole moment brought about by this layer shifts the OSC highest occupied molecular orbital with respect to the Fermi energy of the ferromagnetic contact. This approach allows us full control of the spin band appropriate for charge-carrier extraction, opening up new spintronic device concepts for future exploitation.The development and understanding of new hybrid organic/inorganic interfaces will enable considerable progress in organic spintronics for technological purposes, including processing elements, sensors, memories and conceptually different future applications. In addition to the 'standard' spintronic applications, newly developed interfaces could bring spintronic effects to the field of organic light-emitting diodes (OLEDs), as well as in the fast progressing field of organic field-effect transistors. For example, the injection of carriers with a controlled spin state could enable the amplification of either singlet or triplet exciton states 2 leading to a significant increase in the efficiency of the electroluminescence in OLEDs. Although these considerations are conceptually straightforward, no efficiency amplification has yet been reported in the literature, despite several attempts 3 . The failure of those approaches was caused by the simple reason that light emission can be detected starting from an applied voltage of a few volts, whereas state-of-the-art spin injection in organic materials persists to a maximum of around 1 V (refs 4-6). As yet, this is unexplained. Further complications arise from the fact that various reports on working devices show a wide spread of performances for apparently similar structures, highlighting the issue of reproducibility [7][8][9] . The poor reproducibility is mainly due to the unknown interplay between processing and spin transfer performance and there is little deterministic control of the interface properties. However, it has recently been demonstrated that the insertion of a barrier

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confidence: 99%

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

et al. 2010

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“…5 4.0-4.2 eV is the WF of LSMO exposed to ambient atmosphere and ultrasonically cleaned in acetone and isopropanol prior to putting into the vacuum chamber for the measurement of UPS because of the contaminants on surface. 17,18 In order to remove organic contaminants and increase oxygen stoichiometry on LSMO surface, we used a different ex situ cleaning procedure, i.e., after ultrasonic treatment in organic solvents, LSMO is heated in the solution so-called TL1 ͑Ref. 19͒ ͑5H 2 O, 1NH 4 OH, and 1H 2 O 2 ͒ at 85°C for 5-10 min.…”

Section: Methodsmentioning

confidence: 99%

Electronic structure and molecular orientation of pentacene thin films on ferromagneticLa0.7Sr0.3MnO3

Graziosi

Tang

et al. 2010

Phys. Rev. B

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Pentacene thin films deposited on a ferromagnetic electrode, La 0.7 Sr 0.3 MnO 3 ͑LSMO͒, have been studied using near-edge x-ray absorption fine structure ͑NEXAFS͒, ultraviolet photoemission spectroscopy ͑UPS͒, and atomic force microscopy ͑AFM͒. Here we present electronic structure and molecular orientation of pentacene thin film on LSMO. No evidence related to covalent bonding or significant charge transfer between pentacene and LSMO has been found in the NEXAFS or UPS results. UPS measurements suggest that the vertical ionization potential of pentacene on LSMO is 4.9 eV. Our results extracted from NEXAFS indicate that molecular long axis of pentacene stands on the LSMO substrate surface with a tilt angle of about 22°Ϯ 2°b etween the main molecular axis and the substrate surface normal. AFM images show the terracelike crystalline grain formed by stacking pentacene crystalline layers and a rough crystal-layer spacing of 14-15 Å. Findings deduced from UPS, NEXAFS, and AFM consistently demonstrate that pentacene stands on LSMO with a tilt angle.

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“…Magnetic semiconductors (MSCs) have attracted considerable interest recently due to the active control and manipulation of the charge and spin degrees of freedom of electrons or holes,1 which integrates semiconductor and ferromagnetic functionality of electrons in the same materials and thus creates new functionalities beyond conventional semiconductors that are ideal for spintronic devices 2. Furthermore, MSC materials allow highly efficient spin injection, ideal for new spin field‐effect transistor devices and spin light‐emitting diodes (LEDs) 3.…”

Section: Introductionmentioning

confidence: 99%

Room‐Temperature Ferromagnetic Silver Vanadium Oxide (Ag_1.2V₃O₈): A Magnetic Semiconductor Nanoring Structure

Zhu

Dai

et al. 2010

Adv Funct Materials

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Magnetic nanoring structures are attractive for spintronic devices due to their unique attributes of well‐defined and reproducible magnetic states originating from their characteristic geometry. Almost all previous magnetic nanorings have been exclusively limited to traditional ferromagnetic materials, and a magnetic semiconductor (MSC) nanoring structure has been reported rarely during the past decades. Here, it is demonstrated that room‐temperature ferromagnetic Ag1.2V3O8 nanobelts and nanorings may be achieved by controlled oxidation of the V4+ precursors in an Ag+‐containing aqueous solution. The polarization‐induced self‐coiling of in situ formed Ag1.2V3O8 nanobelts is responsible for the formation of the perfectly circular nanoring geometry. The NEXAFS spectra and the density functional calculations clearly reveal that the electron transfer originates from the hybridization of the doped Ag+ and V4+ atoms, causing ordering of the magnetic moments that give rise to the intrinsic ferromagnetism of the Ag1.2V3O8 structure.

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Energy level alignment and injection barriers at spin injection contacts between La0.7Sr0.3MnO3 and organic semiconductors

Cited by 23 publications

References 45 publications

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Electronic structure and molecular orientation of pentacene thin films on ferromagneticLa0.7Sr0.3MnO3

Room‐Temperature Ferromagnetic Silver Vanadium Oxide (Ag_1.2V₃O₈): A Magnetic Semiconductor Nanoring Structure

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Energy level alignment and injection barriers at spin injection contacts between La0.7Sr0.3MnO3 and organic semiconductors

Cited by 23 publications

References 45 publications

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Electronic structure and molecular orientation of pentacene thin films on ferromagneticLa0.7Sr0.3MnO3

Room‐Temperature Ferromagnetic Silver Vanadium Oxide (Ag1.2V3O8): A Magnetic Semiconductor Nanoring Structure

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Room‐Temperature Ferromagnetic Silver Vanadium Oxide (Ag_1.2V₃O₈): A Magnetic Semiconductor Nanoring Structure