The role of aluminum oxide buffer layer in organic spin-valves performance

Abstract

The electronic structures of the 8-hydroxyquinoline-aluminum (Alq(3))/Al2O3/Co interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduction in the electron injection barrier. The x-ray photoelectron spectroscopy spectra further indicate that the Al2O3 buffer layer prevents the chemical interaction between Alq(3) molecules and Co atoms. X-ray magnetic circular dichroism results demonstrate that a Co layer deposited on an Al2O3 buffered Alq(3) layer shows better magnetic ordering in the interface region than directly deposited Co, which suggests a better performance of spin valves with such a buffer layer. This is consistent with the recent results from [Dediu , Phys. Rev. B 78, 115203 (2008)].<p>Original Publication:Yiqiang Zhan, Xianjie Liu, Elin Carlegrim, Fenghong Li, I Bergenti, P Graziosi, V Dediu and Mats Fahlman, The role of aluminum oxide buffer layer in organic spin-valves performance, 2009, APPLIED PHYSICS LETTERS, (94), 5, 053301.http://dx.doi.org/10.1063/1.3078274Copyright: American Institute of Physicshttp://www.aip.org/</p

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

“…In fact, a cross-section TEM image verified this conclusion. In general, Dediu and co-workers reached the same conclusions, although they found evidence for some Co diffusion into the Alq 3 layer [26,27]. Recently the electronic and magnetic properties of Co doped Alq 3 complex has been investigated by DFT calculations [28].…”

“…There is a debate within the community about whether spin is transported via electrons in the LUMO or holes in the HOMO, and this is still an open question. Some authors claim that spin transport in OSCs is via electrons [23,27,58]. The main argument for electron transport appears to be that in Alq3 hole transport is significantly worse than electron transport [51].…”

“…The interfaces between the FM and the organic layer are not likely to be Ohmic. For example the vacuum level offset at a Co/Alq 3 interface has been found to be 1.4 eV [2]. Hence, one must first consider tunneling as the primary mechanism for charge/spin transfer across such interfaces.…”

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

“…On the other hand, the magnetic property of the FM is also influenced by the contacting OSC. 21,[23][24][25] This reactive modification effect of organic molecules on the magnetic property of FM metals is likely to play a significant role in the property of organic spin valve device as well. Therefore, the design and study of spinterfaces should take all of these points into consideration simultaneously, i.e., the energy level alignment, possible spin-polarization of the interface OSC and possible modification of the interface FM magnetic properties.…”

Of interfaces and spin transport across nanoscale layers

“…Such barriers are applied likewise in spintronics devices based upon graphene [185]. In organic spintronics, where the semiconductors are composed of organic molecules, an insulating barrier has the additional advantage of preventing that pin holes in the organic layers become detrimental for the device's performance [186].…”