  Mechanical polishing of diamond is known to be detrimental to the spin
lifetime and strain environment of near-surface defects. By utilising a
chemical mechanical polishing (CMP) process, we demonstrate that we can achieve
13C-limited spin lifetimes of shallow implanted (<34 nm) NV centres in an
industrially scalable process. We compare spin lifetimes (T2) of three diamonds
processed with CMP with one processed by inductively-coupled plasma reactive
ion etching (ICP-RIE), and observe an increased median T2 of 355 microseconds
in the CMP-processed samples for 15NV centres implanted and annealed under
identical conditions.
