Effect of Negative Thermal Expansion on the Zero-Phonon Line of Implanted Silicon Vacancy Color Centers in Diamond

The charged silicon vacancy (SiV–) color center in diamond can be created by focused ion beam (FIB) implantation, allowing deterministic creation of single photon emitters. Here, we create FIB-implanted SiV– color centers in a diamond substrate spanning 8 orders of magnitude of the ion beam fluence. We show that the SiV– zero-phonon line (ZPL) brightness at 4 K is constant with increasing ion beam fluence, while exhibiting slight inhomogeneous broadening. The temperature-dependent ZPL line shift revealed a blue-shift below 70 K that we attribute to the negative thermal expansion of diamond, showing the SiV– ability as a sensitive probe of its host crystal environment. We demonstrate a versatile line shift model constructed on the basis of the Grüneisen parameter description of the thermal expansion coefficient and the electron–phonon interaction.