Single Chip Dynamic Nuclear Polarization Microsystems

Nuclear magnetic resonance (NMR) methods are powerful tools employed in many fields, including physics, chemistry, material science, biology, and medicine. The use of NMR methodologies in an even wider range of applications is often hindered by the relatively large number of resonating spins needed to achieve a sufficiently large signal-to-noise ratio (SNR) in the available experimental time. An efficient approach to increase the SNR is hyperpolarization where the nuclear spin polarization is increased, e.g., by microwave, optical, and chemistry-based methodologies.Dynamic nuclear polarization (DNP) is one of the most powerful and versatile hyperpolarization methods. Microwave DNP employs a microwave magnetic field to excites the unpaired electrons in the sample under investigation into electron spin resonance (ESR). The ESR excitation of the electrons increases the polarization of the nearby nuclear spins well above the thermal equilibrium value, producing an increase in the SNR up to 660 for ^1H nuclei. A major drawback of DNP is the cost and complexity of the required microwave hardware, especially at high magnetic fields and low temperatures. To overcome this drawback and with the focus on the study of nanoliter and subnanoliter samples, this thesis demonstrates single chip DNP microsystems where the microwave excitation and detection are performed locally on chip without the need of external microwave generators and transmission lines. During the last two decades, the separate integration on a single chip of the front-end electronics of NMR and ESR spectrometers has been demonstrated. In this thesis, the co-integration on a single chip of the front-end electronics of NMR and ESR detectors is presented for the first time. This combination of sensors allows to perform DNP experiments using a single chip having an area of about 2 mm^2. Firstly, a DNP microsystem operating at 10.7 GHz(ESR)/16 MHz(NMR) is integrated into a single CMOS chip. The ESR detector is an oscillator that generates microwave magnetic fields B_{1e} up to 70 uT. The NMR detector is a broadband transceiver operating up to 1 GHz. ^1H DNP-enhanced NMR experiments on liquid and solid samples having a volume of about 1 nL are performed. Overhauser enhancements up to 50 are achieved on TEMPOL/H_2O solutions and solid effect enhancements up to 20 are achieved on BDPA:SEBS at room temperature.Secondly, a DNP microsystem operating at 200 GHz(ESR)/300 MHz(NMR) is integrated into a single SiGe:BiCMOS chip. The ESR detector is a voltage controlled oscillator (VCO) with a tuning range of 8 GHz which generates a B_{1e} up to a few G. The NMR detector is a broadband receiver operating up to 1 GHz. ^1H DNP experiments on BDPA:PS samples having a volume of 2 nL and 125 pL show solid effect enhancements up to 50 and 10 at 15 K and 100 K, respectively. A single chip DNP array is also demonstrated. The array has four frequency locked 200 GHz VCOs which interrogates a sample volume an order of magnitude larger compared to the single VCO. Measurements on BDPA:PS samples having a volume of 1 nL show solid effect enhancements up to 20 at 200 K.Finally, a In_{0.7}Ga_{0.3}As high electron mobility transistor (HEMT) technology is investigated for the possible integration of low power single chip DNP microsystems that might be able to operate down to 1 K and below. HEMT transistors and ultra low power oscillators operating at 11 GHz and 35 GHz are investigated down to 1.4 K.