A static and “magic-angle” sample-spinning nuclear magnetic resonance spectroscopic study of 11B in Si[B]. An analysis of spin—spin and spin—lattice relaxation behavior in the metallic state

Abstract

We have investigated the signal intensity, lineshape, spin—lattice and spin—spin (spin-echo decay) relaxation behavior of 11B nuclei in a Si[B] extrinsic semiconductor in the metallic state, as a function of magnetic field strength and temperature. We find that essentially all boron spins are in a highly symmetric environment, characterized by a mean nuclear quadrupole coupling constant ( e 2 qQ/ h) of ≈ 12 kHz. The spin—lattice relaxation is Korringa like, with a T 1 T ≈ 550 s K, at both 5 and 300 K, indicating a mean Knight shift of ≈ 70 ppm. The spin—spin relaxation time, T 2E, is 25 ms at 8.45 T, independent of temperature, or magnetic field strength in the range 2.35 to 11.7 T, at 300 K. The T 2E value is in good agreement with the predictions of a model of homonuclear dipolar interactions within metallic Si[B] clusters.