Silicon spin vacuum: Isotopically enriched silicon-on-insulator28 and silicon28 from ultrahigh fluence ion implantation

Abstract

Isotopically enriched silicon (Si) can greatly enhance qubit coherence times by minimizing naturally occurring Si29 which has a nonzero nuclear spin. Ultrahigh fluence Si28 ion implantation of bulk natural Si substrates was recently demonstrated as an attractive technique to ultrahigh Si28 isotopic purity. In this work, we apply this Si28 enrichment process to produce Si28 and Si28-on-insulator (SOI) samples. Experimentally, we produced a Si28 sample on natural Si substrate with Si29 depleted to 7 ppm (limited by measurement noise floor) that is at least 100 nm thick. This is achieved with an ion energy that results in a sputter yield of less than one and an ultrahigh ion fluence, as support..