Theoretical investigation of preparation pathways that enhance the equilibrium yield of negatively ionized tin-vacancy centers in N-doped diamond

The elucidation of the mechanism of SnV− formation in diamond is especially important as the SnV− color center has the potential to be a superior single-photon emitter when compared to the NV and to other Group IV impurity-vacancy color centers in diamond. The typical formation of SnV involves placing Sn in diamond by ion implantation, but the formation of a charged SnV species requires an additional complication. This complication is related to the energy cost associated with electronic transitions within the host diamond. Effectively, producing the SnV− charge state using an electron obtained from a band edge of the host diamond is less energetically favorable than having the SnV− receive an electron from a neighboring donor dopant. Among donor dopants, substitutional N (NC) is always present in even the purest synthetic or natural diamond sample. The mechanism of electron donation by NC has been proposed by Collins for charging the NV in diamond and it has been used to interpret many experimental results. Therefore, in this paper, we use density functional theory (DFT) to explore the pathways for the formation of the SnV− charge state due to electron donation arising from the presence of NC in the host diamond. Explicitly, defect concentrations are calculated in equilibrium in each of the explored pathways to determine the yield of the SnV− throughout each of the pathways. The importance of our work is to suggest experimental ways of enhancing the yield of charged states like the SnV− in diamond for transformative applications in optoelectronics and quantum information.