Microwave field mapping for EPR-on-a-chip experiments

Area of Science:

• Physics
• Chemistry
• Materials Science

Background:

• Electron paramagnetic resonance-on-a-chip (EPRoC) devices utilize voltage-controlled oscillators (VCOs) for EPR signal excitation and detection.
• EPRoC technology offers access to novel sample environments, overcoming limitations of traditional resonator-based EPR.
• Previous EPRoC applications have shown high-resolution spectra across various frequencies (7-360 GHz) and spin centers.

Purpose of the Study:

• To enable quantitative measurements with EPRoC devices, this study aimed to determine the spatial distribution of the B1 field generated by VCOs.
• Characterize the B1 field distribution of a 12-coil VCO array EPRoC operating at 14 GHz.
• Determine the sensitive volume of the EPRoC array for precise EPR analysis.

Main Methods:

• Investigated frequency modulation-recorded EPR spectra of point-like and thin-film samples.
• Varied sample positions in three dimensions relative to the EPRoC device.
• Compared experimental EPR spectra with COMSOL simulations of B1-field intensity.

Main Results:

• The spatial distribution of the B1 field from a 12-coil VCO array EPRoC was mapped.
• Experimental data correlated well with COMSOL simulations of B1-field intensity.
• The sensitive volume of the EPRoC array was quantified at approximately 19 nanoliters.

Conclusions:

• Accurate knowledge of B1 field distribution is crucial for quantitative EPRoC measurements.
• The characterized EPRoC device demonstrates potential for precise analytical applications.
• Further implications for diverse EPR applications are discussed based on these findings.