Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions

Zhan, Yiqiang; Holmström, Erik; Lizárraga, Raquel; Eriksson, Olle; Liu, Xianjie; Li, Fenghong; Carlegrim, Elin; Stafström, Sven; Fahlman, Mats

doi:10.1002/adma.200903556

Cited by 76 publications

(74 citation statements)

References 27 publications

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“…When Alq 3 was adsorbed on LSMO only a single N(1s) peak was observed, which indicated a very small perturbation of the electronic structure of Alq 3 . In contrast, a very large perturbation in the electronic structure was observed for Alq 3 adsorption on Co and Fe surfaces [24]. In the XPS spectra three peaks were observed near 400, 398.5, and 397 eV for Alq 3 adsorption on Co and Fe.…”

mentioning

confidence: 80%

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

Drew

Szulczewski

Nuccio

et al. 2011

Physica Status Solidi (b)

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Interfaces between dissimilar materials are critical to the performance of many electronic devices. In electrical devices where the active transport is through an organic semiconductor (OSC) layer there are metallic electrodes to supply and remove the charge carriers. At metal/molecule and molecule/metal interfaces the electrical contact is usually not Ohmic. As a result, in most metal-organic semiconductors-metal devices charge injection is mainly governed by tunneling across the barriers. When the metal electrodes are ferromagnetic the density of occupied and unoccupied electronic states is spindependent, which presents further subtleties to the electron transfer. In this article we summarize some of the important experimental results that have advanced our understanding of spin-polarized electron transfer across ferromagnetic metal (FM)/OSC interfaces. In particular, we highlight key spectroscopic studies that have revealed insights into the nature of the electronic structure between OSCs and FMs, in particular between Alq 3 and Co and Fe surfaces. We discuss the relationship between energy level diagrams for these systems and transport measurements made on spin-valve devices.

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mentioning

confidence: 80%

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

Drew

Szulczewski

Nuccio

et al. 2011

Physica Status Solidi (b)

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“…There are several proposed mechanisms for the formation of the interface dipole 26 . The injection barriers of holes at interfaces between Alq 3 and cobalt 15 or iron 27 were determined by photoelectron spectroscopy methods and the position of the LUMO energy level of the Alq 3 molecule was deduced from the HOMO-LUMO gap. Recently, both HOMO and LUMO energy levels at surfaces were directly determined by ballistic-electron-emission spectroscopy 28 and energy level alignments at Alq 3 /Fe and Alq 3 /Al interfaces were measured.…”

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confidence: 99%

Adsorption of tris(8-hydroxyquinoline)aluminum molecules on cobalt surfaces

Wang

Han

et al. 2012

Phys. Rev. B

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We studied the adsorption of tris(8-hydroxyquinoline)aluminum (Alq3) molecules on cobalt surfaces using density functional theory with the generalized gradient approximation. The van der Waals interaction between Alq3 molecules and cobalt surfaces was included by the dispersion correction. Magnetization of Alq3 molecules, adsorption energies and bonding energies were obtained for smooth and defective surfaces and for various molecule-surface configurations. Electronic structures were analyzed for states that are relatively stable. We found that both the permanent electric dipole of Alq3 molecules and charge redistribution near the interface contribute to the interface dipole, and the interface dipole due to charge redistribution is important to determine work function of a Co/Alq3 surface. Our calculated energy level alignment at interfaces is consistent with experimental observations.

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“…From the so-called secondary electron cutoff the work function of Fe can be determined as ~4.6 eV, corresponding to the typical value in literature. 19 Once TCNQ molecules adsorb on Fe to form the interface, an interface dipole appears, achieving a maximum value of ~0.9 eV. Consequently the work function increases to higher values and reaches a value of ~5.5 eV very quickly, when TCNQ is still a submonolayer.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…There are many reports on the interfacial spin-polarization of organic molecules adsorbed on FM films, [19][20][21][22] which is believed to arise from orbital hybridization between OSC and FM atoms. On the other hand, the magnetic property of the FM is also influenced by the contacting OSC.…”

Section: Introductionmentioning

confidence: 99%

Energy level alignment and interactive spin polarization at organic/ferromagnetic metal interfaces for organic spintronics

Sun

Zhan

Shi

et al. 2014

Organic Electronics

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ABSTRACT:Energy level alignment and spin polarization at tetracyanoquinodimethane/Fe and acridine orange base/Fe interfaces are investigated by means of photoelectron spectroscopy and X-ray magnetic circular dichroism (XMCD), respectively, to explore their potential application in organic spintronics. Interface dipoles are observed at both hybrid interfaces, and the work function of Fe is increased by 0.7 eV for the tetracyanoquinodimethane (TCNQ) case, while it is decreased by 1.2 eV for the acridine orange base (AOB) case. According to XMCD results, TCNQ molecule has little influence on the spin polarization of Fe surface. In contrast, AOB molecule reduces the interfacial spin polarization of Fe significantly. Induced spin polarization of the two organic molecules at the interfaces is not observed. The results reveal the necessity of investigating the magnetic property changes of both the OSC and the FM during the process of energy level alignment engineering.

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Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions

Cited by 76 publications

References 27 publications

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

The role of interfaces in organic spin valves revealed through spectroscopic and transport measurements

Adsorption of tris(8-hydroxyquinoline)aluminum molecules on cobalt surfaces

Energy level alignment and interactive spin polarization at organic/ferromagnetic metal interfaces for organic spintronics

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