Millimeter-Wave Band Resonator with Surface Coil for DNP–NMR Measurements

In this study, we developed a surface coil with a meanderline shape for nuclear magnetic resonance (NMR) combined with a Fabry–Perot resonator (FPR) for millimeter-wave band electron-spin resonance (ESR). Our goal was to perform both NMR and ESR measurements with high sensitivity, in particular for thin samples, such as a silicon wafer. We measured NMR signals using a variety of meanderline coil shapes and determined the optimal turn number of the meanderline as well as the clearance length between the lines. The FPR consisted of spherical and flat mirrors, where the latter was constructed of a thin gold layer with the meanderline underneath. We observed that the meanderline provided high sensitivity when the gold layer was sufficiently thin at approximately 16 nm. We also measured millimeter-wave ESR from a thin sample of phosphorous-doped silicon with the developed FPR with the meanderline.