Preprints
https://doi.org/10.5194/mr-2021-40
https://doi.org/10.5194/mr-2021-40

  03 May 2021

03 May 2021

Review status: this preprint is currently under review for the journal MR.

Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor

Silvio Künstner1, Anh Chu2, Klaus-Peter Dinse1,5, Alexander Schnegg3, Joseph E. McPeak1, Boris Naydenov1, Jens Anders2,4, and Klaus Lips1,5 Silvio Künstner et al.
  • 1Berlin Joint EPR Laboratory and EPR4Energy, Department Spins in Energy Conversion and Quantum Information Science (ASPIN), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
  • 2Institute of Smart Sensors, Universität Stuttgart, 70569 Stuttgart, Germany
  • 3EPR4Energy, Max-Planck-Institut für chemische Energiekonversion, 45470 Mülheim an der Ruhr, Germany
  • 4Center for Integrated Quantum Science and Technology (IQST), Stuttgart and Ulm, Germany
  • 5Berlin Joint EPR Laboratory, Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany

Abstract. Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species in many scientific fields, including materials science and the life sciences. Common EPR spectrometers use electromagnets and microwave (MW) resonators, limiting their application to dedicated lab environments. Here, we present an improved design of a miniaturized EPR spectrometer implemented on a silicon microchip (EPR-on-a-chip, EPRoC). In place of a microwave resonator, EPRoC uses an array of injection-locked voltage-controlled oscillators (VCOs), each incorporating a 200 µm diameter coil, as a combined microwave source and detector. The individual miniaturized VCO elements provide an excellent spin sensitivity reported to be about 4 × 109 spins/√Hz, which is extended by the array over a larger area for improved concentration sensitivity. A striking advantage of this design is the possibility to sweep the MW frequency instead of the magnetic field, which allows the use of smaller, permanent magnets instead of the bulky and power-hungry electromagnets required for field-swept EPR. Here, we report rapid scan EPR (RS-EPRoC) experiments performed by sweeping the frequency of the EPRoC VCO array. RS-EPRoC spectra demonstrate an improved SNR by approximately two orders of magnitude for similar signal acquisition times compared to continuous wave (CW-EPRoC) methods, which may improve the absolute spin and concentration sensitivity of EPR-on-a-Chip at 14 GHz to about 6 × 107 spins/√Hz and 3.6 nM/√Hz, respectively.

Silvio Künstner et al.

Status: open (until 31 May 2021)

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Silvio Künstner et al.

Silvio Künstner et al.

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Short summary
Electron paramagnetic resonance (EPR) spectroscopy is the method of choice to investigate and quantify paramagnetic species. We present the application of an unconventional EPR detection method, rapid scan EPR, to enhance the sensitivity on an improved design of a miniaturized EPR spectrometer implemented on a silicon microchip. Due to its size, it may be integrated into complex and harsh sample environments enabling in situ or operando EPR measurements that have previously been inaccessible.