Measurement of hyperfine coupling constants of muoniated radicals in small molecule semiconductors

L Schulz,M Willis,S Zhang,F L Pratt,C Bernhard,K Wang,L Nuccio,P Murahari,A J Drew,J S Lord,N A Morley

doi:10.1088/1742-6596/551/1/012042

Abstract

We report the hyperfine coupling constants of muoniated radicals formed in a number of organic semiconductors, via transverse field measurements taken in the Paschen Back limit, and compare the results to avoided level crossing resonances. Five muoniated radicals are found in tetracene, despite there only being three potential non-equivalent bonding sites, and we suggest that this might be down to crystal packing effects. For 6,13-bis(triisopropylsilylethynyl) pentacene and 6,13-bis(trimethlsilylethynyl)-pentacene, we demonstrate that the transverse field data supports the previously published avoided level crossing resonances.

Highlights

The investigation of organic materials (OSC) is vital for the advancement of organic electronics
The muon spin rotation/relaxation/resonance (MuSR) experiment was performed on polycrystalline samples of the organic semiconductors tetracene, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and 6,13bis(trimethlsilylethynyl)-pentacene (TMS-pentacene)
The transverse field (TF) measurements were taken in the Paschen-Back regime at a temperature of 10 K using the GPS spectometer of the Paul-Scherrer-Institute, Switzerland, and the avoided level crossing (ALC) spectra were taken on the HiFi instrument at the ISIS Pulsed Muon Source, UK

Summary

Introduction

The investigation of organic materials (OSC) is vital for the advancement of organic electronics. A more specialized technique, the low-energy muon spin rotation technique, allowed for implanting muons at buried interfaces of fully functional organic-based spintronic devices, thereby enabling the measurement of spin injection into the organic spacer layer [4]. This resulted in a better understanding of their functionality [4] and how the spintronic property of these devices can be engineered [5]. We report avoided level crossing (ALC) and transverse field (TF) measurements taken in the Paschen Back limit to determine the hyperfine coupling (HFC) constant of muoniated radicals in a number of organic semiconductors [6, 7, 8]. Practically in high TF experiment, these frequencies can be accessed either by conventional Fourier transforms or by fitting the time dependent asymmetry A0 directly to a sum of relaxed oscillations (two frequencies f12 and f34 per muonium site plus the diamagnetic fraction)

Results and Discussion

10 K 300 K

Conclusions