Quadrupole Shift of Nuclear Magnetic Resonance of Donors in Silicon at Low Magnetic Field

TL;DR

This paper investigates unexpected large shifts in nuclear magnetic resonance frequencies of donors in silicon, attributing them to quadrupole interactions caused by defect-induced electric field gradients, with a quantitative model supporting the findings.

Contribution

It provides the first detailed analysis linking defect-induced electric field gradients to quadrupole shifts in donor NMR in silicon, supported by a molecular orbital theory model.

Findings

Observed NMR shifts >1 MHz for donors in silicon.

Attribution of shifts to electric field gradients from implantation defects.

Quantitative modeling aligns with experimental data.

Abstract

Shifts from the expected nuclear magnetic resonance frequencies of antimony and bismuth donors in silicon of greater than a megahertz are observed in electrically detected magnetic resonance spectra. Defects created by ion implantation of the donors are discussed as the source of effective electric field gradients generating these shifts via quadrupole interaction with the nuclear spins. The experimental results are modeled quantitatively by molecular orbital theory for a coupled pair consisting of a donor and a spin-dependent recombination readout center.