OVERHAUSER-SHIFT MEASUREMENTS ON SI-P NEAR THE METAL-INSULATOR-TRANSITION

The interaction of both delocalized conduction electrons and localized electrons with nuclei in Si doped with P near the insulator-metal transition has been studied by the Overhauser-shift technique. By a direct method the dynamic nuclear polarization enhancement, the nuclear-spin-lattice relaxation rate, and the Overhauser shift have been determined simultaneously. The conduction-electron density \phi(0)\2 at the Si nucleus is obtained. The nuclei in the vicinity of the donor atoms are responsible for the large paramagnetic shift of the Si-29 NMR frequency. The nuclear-spin-lattice relaxation is non-monoexponential and originates from silicon nuclei both close to and distant from the donor atom.