Room-temperature air-stable spin transport in bathocuproine-based spin valves

Abstract

Organic semiconductors, characterized by weak spin-scattering mechanisms, are attractive materials for those spintronic applications in which the spin information needs to be retained for long times. Prototypical spin-valve devices employing organic interlayers sandwiched between ferromagnetic materials possess a figure of merit (magnetoresistance (MR)) comparable to their fully inorganic counterparts. However, these results are a matter of debate as the conductivity of the devices does not show the expected temperature dependence. Here we show spin valves with an interlayer of bathocuproine in which the transport takes place unambiguously through the organic layer and where the electron spin coherence is maintained over large distances (460 nm) at room temperature. Additionally, the devices show excellent air stability, with MR values almost unaltered after 70 days of storage under ambient conditions, making bathocuproine an interesting material for future spintronic applications.

Active Morphology Control for Concomitant Long Distance Spin Transport and Photoresponse in a Single Organic Device

“…[ 5,15,16 ] However, to develop new physical properties in organic spin valves, the (spin) charge carrier transport should really occur in and be dominated by the organic semiconductor (via hopping) rather than by metallic fi laments or the injection barrier. [ 14 ] From the molecular side, an obvious choice for improving spin charge carrier injection would be a compound whose energy level responsible for electronic transport matches well the Fermi level of the ferromagnetic electrodes used.…”

“…[ 2,21 ] Besides, F 16 CuPc is an air-stable organic semiconductor, [ 25 ] being this property crucial for any application of organic spintronic devices. [ 5,27 ] Our vertical OSV devices have a typical vertical cross-bar structure with the following layers: Co (11 nm)/AlO x (1.5 nm)/ F 16 CuPc (15-180 nm)/Ni 80 Fe 20 (NiFe, 11 nm) (see Figure 1 ). Co and NiFe electrodes act as the source and detector of the spinpolarized transport in the F 16 CuPc spacer.…”

Spin current relaxation time in thermally evaporated pentacene films

“…3 Until now, the spin transport properties of some molecular materials have been investigated. [4][5][6][7][8][9] We have focused on pentacene molecular films prepared by thermal evaporation as one candidate material for the spin transport, in terms of the good crystallinity even in the thermally evaporated films, and the high electrical conductivity without any dopants. 10 Moreover, pentacene shows the photo-conductivity for visible light, 11 where the spin transport properties of pentacene can be controlled through visible light irradiation.…”

Recent progress in organic spintronics

“…For some systems, MR is observed in the tunneling regime while it is absent in the thermally activated transport regime [58], supporting the view that MR in organic spin valves may generally be associated with tunneling effects. On the other hand, other systems have been reported that do exhibit significant MR in combination with a strong temperature dependence of the conductivity [59,60]. In addition, strong isotope effects have been reported in organic spin valves based on deuterated and hydrogenated versions of the same conjugated polymer [28], supporting the idea that spin-polarized transport in the organic layer plays a dominant role.…”

“…This strongly limits the freedom for tuning injection barrier heights. A recent study on Co/AlOx/bathocuproine(BCP)/Ni 80 Fe 20 spin valves [59], where the properties of the AlOx barriers were varied and different barrier heights were found, suggests that this might nevertheless be of considerable importance. For a BCP thickness up to 60 nm, room-temperature MR of a few percent, in combination with a strongly temperature dependent conductivity consistent with thermally activated hopping, was observed for devices with low injection-barrier heights (determined from ln(I/V 2 )…”