Injection, transport and detection of spin currents in organic semiconductors

Research on spin current transport has so far been concentrated around metals, ferromagnetic insulators and inorganic semiconductors, but is still relatively scarce in organic semiconductors. Recently, there have been a few attempts at exploring spin pumping into polymers, which showed promising results. The main part of this thesis provides a detailed experimental analysis of spin pumping into an organic semiconductor PBTTT in vertical and lateral device architectures exploiting inverse spin-Hall effect as the detection method. We have discovered fundamental mistakes in previous publications on this topic and offered a way to rectify them with extended angular dependence measurements. In this way, we could distinguish spin pumping signal from other spurious effects. Our results from lateral spin pumping experiments expose drawbacks in the current device architecture and show no convincing proof of achieving spin current transport through PBTTT. Experiments with vertical spin pumping aimed at exploring the most optimal fabrication parameters that maximise the spin pumping signal and minimise spurious effects. We attempted spin pumping through trilayers using gold or undoped PBTTT as the transport layer and revealed further difficulties associated with the vertical architecture. The second part of this thesis proposes a new way to detect spin currents in organic semiconductors based on dynamic nuclear polarisation and organic magnetoresistance. It uses the spin-Hall effect as the source of spin currents and is therefore free from the numerous spurious effects that accompany the spin pumping method. We have conducted initial measurements with this new experimental method and identified ways to improve its design.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Skalski, Piotr

Advisor dc:contributor.advisor

• Sirringhaus, Henning

• spin
• spin current
• pure spin current
• FMR
• spin pumping
• spin hall effect
• inverse spin hall effect
• organic magnetoresistance
• dynamin nuclear polarisation
• organic semiconductor
• spin rectification effects

Licence

• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0003-3102-9837

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/339111