Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI 125Te+ donors implanted into natural Si at depths as shallow as 20~nm. We show that surface band-bending can be used to ionise such near-surface Te to spin-active Te+ state, and that optical illumination can be used further to control the Te donor charge state. We examine spin activation yield, spin linewidth, relaxation (T1) and coherence times (\ttwo) and show how a zero-field 3.5~GHz `clock transition' extends spin coherence times to over 1~ms, which is about an order of magnitude longer than other near-surface spin systems.
@article{arxiv.2108.07654,
title = {Spin coherence of near-surface ionised $^{125}$Te$^+$ donors in silicon},
author = {Mantas Šimėnas and James O'Sullivan and Oscar W. Kennedy and Sen Lin and Sarah Fearn and Christoph W. Zollitsch and Gavin Dold and Tobias Schmitt and Peter Schüffelgen and Ren-Bao Liu and John J. L. Morton},
journal= {arXiv preprint arXiv:2108.07654},
year = {2022}
}