Integration of the sensitivity-relevant electronics of nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectrometers on a single chip is a promising approach to improve the limit of detection, especially for samples in the nanoliter and subnanoliter range. Here, we demonstrate the cointegration on a single silicon chip of the front-end electronics of NMR and ESR detectors. The excitation/detection planar spiral microcoils of the NMR and ESR detectors are concentric and interrogate the same sample volume. This combination of sensors allows one to perform dynamic nuclear polarization (DNP) experiments using a single-chip-integrated microsystem having an area of about 2 mm2. In particular, we report 1H DNP-enhanced NMR experiments on liquid samples having a volume of about 1 nL performed at 10.7 GHz­(ESR)/16 MHz­(NMR). NMR enhancements as large as 50 are achieved on TEMPOL/H2O solutions at room temperature. The use of state-of-the-art submicrometer integrated circuit technologies should allow the future extension of the single-chip DNP microsystem approach proposed here up the THz­(ESR)/GHz­(NMR) region, corresponding to the strongest static magnetic fields currently available. Particularly interesting is the possibility to create arrays of such sensors for parallel DNP-enhanced NMR spectroscopy of nanoliter and subnanoliter samples.

High-electron-mobility transistors (HEMTs) based on 2-D electron gases (2DEGs) in III-V heterostructures have superior mobility compared with the transistors of silicon-based complementary metal-oxide-semiconductor technologies. The large mobility makes them attractive not only for low-noise and high-power microwave applications but also for low-power applications down to deep cryogenic temperatures. Here, we report on the design and characterization of a low-power HEMT LC Colpitts oscillator operating at 11 GHz whose minimum power consumption is 90 µW at 300 K and 4 µW at 1.4 K. The fully integrated oscillator is based on a single HEMT transistor having a gate length of 70 nm and realized using a 2DEG in In 0.7 Ga 0.3 As. The power consumption of the realized oscillator is the lowest reported in the literature so far for an LC oscillator operating in the same frequency range. In order to investigate the behavior of the oscillator, we also performed a detailed characterization of a stand-alone HEMT transistor from 1.4 to 300 K with a static magnetic field from 0 to 8 T. From the extracted values of the transistor parameters, we estimate and compare the minimum power necessary to start-up oscillations for two different Colpitts topologies.

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