Electron transport and spin phenomena in hybrid organic/inorganic systems


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Naber, Wouter Johannes Marinus (2010) Electron transport and spin phenomena in hybrid organic/inorganic systems. thesis.

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Abstract:This thesis describes several experiments in hybrid organic/inorganic systems, in which electron transport and/or spin behavior is studied.

The basic concepts of organic electronics and spintronics are given, to understand the described spin-valve experiments. The problems and obstacles for injecting a spin-polarized current into organic materials and the potential of using organic single-crystals in spintronic devices are discussed.

Different methods for fabricating organic single-crystal FET devices with FM electrodes are explained. First, the growth of organic single-crystals is discussed. Then, the fabrication of FM electrodes with shadow masks, photo- and e-beam lithography is explained.

The interface of fabricated FM electrodes and organic materials is investigated. UV photoemission spectroscopy and X-ray photoelectron spectroscopy are performed to study the energy level alignment. The effect of the lithography processes on the spin injection properties of the FM electrode and a cleaning step applied to the interfaces are investigated.

Measurements on rubrene single-crystal FETs with FM/tunnel barrier electrodes are discussed. The critical spin-valve properties of these devices are investigated and it is shown that this FET has the potential of being used as a spin valve. The current flowing through the device can be fitted to a back-to-back Schottky model, which show that electrons are injected via a well-defined tunnel barrier fabricated on top of the FM electrodes.

Transferring Au electrodes to organic single-crystals by soft elastomeric stamps, with and without the facilitation of organic molecules, is investigated. Measurements in the space-charged-limited-current regime and on FET devices are presented and discussed.

FM nanoparticles (NPs), capped with organic ligands, are discussed. A systematic study of the annealing of these NPs in solution at relative low temperatures is described. The annealing is needed to obtain high magnetocrystalline anisotropy. The low-temperature annealing leaves the organic ligands intact, which can be used for patterning.

Experiments are performed on two-dimensional organic spin systems to study the interaction of the spins with their environment. The system consists of a thin Au film covered with a monolayer of molecules containing an unpaired spin. The signature of the Kondo effect, a local resistance minimum as a function of temperature, is observed under certain conditions. The behavior of this effect in the presence of a magnetic field is also investigated.
Item Type:Thesis
Faculty:
Electrical Engineering, Mathematics and Computer Science (EEMCS)
Research Group:
Link to this item:http://purl.utwente.nl/publications/70123
Official URL:http://dx.doi.org/10.3990/1.9789036529884
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