Removal of ${}^{210}$Pb by Etch of Crystalline Detector Sidewalls

A potential source of dominant backgrounds for many rare-event searches or screening detectors is from radon daughters, specifically ${}^{210}$Pb, deposited on detector surfaces, often during detector fabrication. Performing a late-stage etch is challenging because it may damage the detector. This paper describes a late-stage etching technique that reduces surface ${}^{210}$Pb and ${}^{210}$Po by $>99\times$ at 90% C.L.