Identifying impurities in a silicon substrate by using a superconducting flux qubit

TL;DR

This study demonstrates a superconducting flux qubit-based magnetometer's ability to detect and analyze impurities in silicon substrates, revealing multiple spin sources and surface dangling bonds with high sensitivity.

Contribution

It introduces a novel application of superconducting flux qubits for impurity detection in silicon, identifying specific spin sources and estimating high spin sensitivity.

Findings

Detected multiple spin sources in silicon substrate

Identified dangling bonds as a spin 1/2 system

Estimated magnetometer sensitivity as 12 spins/√Hz

Abstract

A bismuth-doped silicon substrate was analyzed by using a magnetometer based on a superconducting flux qubit. The temperature dependence of the magnetization indicates that the silicon substrate contains at least two signal sources, intentionally doped bismuth spins and a spin 1/2 system with a ratio of 0.873 to 0.127. In combination with a conventional electron spin resonance spectrometer, a candidate origin of the spin 1/2 system was identified as a dangling bond on the silicon surface. In addition, the spin sensitivity of the magnetometer was also estimated to be 12 spins/$\sqrt{\mathrm{Hz}}$ by using optimized dispersive readout.