Preamplified planar microcoil on GaAs substrates for microspectroscopy

In the course of the publication the design, fabrication, and experimental evaluation of a planar microcoil for nuclear magnetic resonance (NMR) spectroscopy with a 360 μm inner diameter integrated to a low-noise metal–semiconductor field-effect transistor is presented. The impedance matching of the coil and transistor was achieved by adjusted coil geometry, while an appropriate microfabrication process including air bridge contacts and a multilayer metal stack was developed for the necessary susceptibility matching of the coil metallization. The NMR spectra of experiments in an 11.75 T magnet (corresponding to 500 MHz) show the amplification of the signal by the integrated transistor. Due to previous experiments, we wanted to ensure that the whole signal emerged from the sensitive volume of the microcoil.