Single chip microsystems for electron spin resonance spectroscopy and inductive proximity sensing

Electron spin resonance spectroscopy is a non-invasive technique to explore paramagnetic systems. ESR spectrometers operate in a wide range of frequencies from 1 MHz to 1 THz, and at temperatures from 1000 K to mK. Boero's group pioneered a novel approach for ESR spectroscopy by integrating sensitive components in a single chip. They achieved a 2 orders of magnitude improvement in sensitivity for nL samples compared to commercial spectrometers with spin sensitivities of 10^10 spins/Hz^(1/2) for uL samples. To enhance sensitivity further, research focused on increasing excitation frequency, optimizing microcoil size for the target volume, and operating at cryogenic temperatures. These advancements led to substantial improvements, as recent studies report single chip CW-ESR detectors capable of achieving spin sensitivities of 10^6 spins/Hz^(1/2). Pulsed techniques have been widely integrated into single-chip NMR systems, while their implementation in single-chip pulsed ESR microsystems remains challenging due t