Double and single peaks in nuclear magnetic resonance spectra of natural and ²⁹Si-enriched single-crystal silicon

We report the nuclear magnetic resonance (NMR) spectra of phosphorus-doped single-crystal silicon, enriched to 97% ²⁹Si, which display double as well as single peaks as the sample is rotated with respect to the static magnetic field. It is shown that the shape and the width of the NMR lines are predominantly due to nuclear dipolar interactions. We provide a theoretical model to determine the strength of the weaker scalar coupling between neighboring ²⁹Si nuclei. For naturally abundant single-crystal silicon (4.7% ²⁹Si), the anisotropic dipolar interaction is visible as well in the NMR spectra. We have observed small side peaks for particular orientations of the crystal axes and we show that the intensity of the side peaks contains information on the distribution of ²⁹Si atoms in the ²⁸Si matrix.