Efficiency Optimization of Ge‐V Quantum Emitters in Single‐Crystal Diamond upon Ion Implantation and HPHT Annealing

Abstract

The authors report on the characterization at the single‐defect level of germanium‐vacancy (GeV) centers in diamond produced upon Ge− ion implantation and different subsequent annealing processes, with a specific focus on the effect of high‐pressure‐high‐temperature (HPHT) processing on their quantum‐optical properties. Different post‐implantation annealing conditions are explored for the optimal activation of GeV centers, namely, 900 °C 2 h, 1000 °C 10 h, 1500 °C 1 h under high vacuum, and 2000 °C 15 min at 6 GPa pressure. A systematic analysis of the relevant emission properties, including the emission intensity in saturation regime and the excited state radiative lifetime, is performed on the basis of a set of ion‐implanted samples, with the scope of identifying the most suitable conditions for the creation of GeV centers with optimal quantum‐optical emission properties. The main performance parameter adopted here to describe the excitation efficiency of GeV centers as single‐photon emitters is the ratio between the saturation optical excitation power and the emission intensity at saturation. The results show an up to eightfold emission efficiency increase in HPHT‐treated samples with respect to conventional annealing in vacuum conditions, suggesting a suitable thermodynamic pathway toward the repeatable fabrication of ultra‐bright GeV centers for single‐photon generation purposes.

Structural formation yield of GeV centers from implanted Ge in diamond

“…However, while it cannot be ruled out that this might initially increase the amount of GeV centers, the problem remains that a subsequent annealing step, which is required to achieve the optical properties, most likely converts the majority of them to substitutional Ge s . Recently, encouraging results were published regarding the enhancement of optical properties of GeV centers, in particular optical excitation power to reach saturation emission, created by means of ion implantation and high-pressure-high-temperature processing (HPHT, 15 min at 2000 • C and 6 GPa) [65]. However, this study did not assess the efficiency of formation of the optically active GeV − centers.…”

Solid-State Color Centers for Single-Photon Generation

“…The main strength of these classes of color centers lies in their room-temperature operation, although there are unavoidable limitations in the degree of indistinguishability, and in their high photon emission rates (above 10 6 photons/s for several classes of defects [23,39,48]). Moreover, diamond color centers can be straightforwardly fabricated by means of the incorporation of selected impurities by ion implantation due to the relative simplicity of their defective structure, although their formation efficiency heavily depends on post-implantation activation processes [41,[49][50][51][52]. Furthermore, laser writing has recently disclosed a novel approach in diamond-defect engineering for device fabrication, unlocking in-plane-high-spatial accuracy in the controlled placement of single emitters [51] and new perspectives for their integration in diamond chips [53].…”

“…The fabrication by means of ion implantation has been amply demonstrated for several classes of diamond color centers. Diamond is currently the only material for which an extensive scientific literature is available on the optimization of the formation yield of color centers by several approaches, spanning from surface chemical functionalization [213] to co-doping [49] and post-implantation processes [52].…”