Screening and engineering of colour centres in diamond

Abstract

We present a high throughput and systematic method for screening of colour centres in diamond. We aim at the search and reproducible creation of new optical centres, down to the single level, potentially of interest for the wide range of diamond-based quantum applications. The screening method presented here should moreover help identifying some already indexed defects among hundreds in diamond [1] but also some promising defects of still unknown nature, such as the recently discovered ST1 centre [2,3]. We use ion implantation in a systematic manner to implant several chemical elements. Ion implantation has the advantage to address single atoms inside the bulk with defined depth and high lateral resolution, but the disadvantage of defect production such as vacancies. The sample is annealed in vacuum at different temperatures (between 600°C and 1600°C with 200°C steps) and fully characterised at each step in order to follow the evolution of the defects: formation, dissociation, diffusion, reformation and charge state, at the ensemble level and, if possible, at the single centre level. We review the unavoidable ion implantation defects (with the example of the GR1 and 3H centres), discuss ion channeling and thermal annealing and estimate the diffusion of vacancies, nitrogen and hydrogen. We use different characterisation methods best suited for our study (from widefield fluorescence down to sub-diffraction optical imaging of single centres) and discuss reproducibility issues due to diamond and defect inhomogeneities. Nitrogen is also implanted as a reference, taking advantage of the large knowledge on NV centres as a versatile sensor in order to retrieve or deduce the conditions and local environment in which the different implanted chemical elements are embedded. We show here the preliminary promising results of a long-term study and focus on the elements O, Mg, Ca, F and P, from which fluorescent centres were found.

Coulomb-driven single defect engineering for scalable qubits and spin sensors in diamond

“…Qubits in diamond based on the nitrogen-vacancy (NV) centre are widely implemented for a large range of applications like quantum information processing 1 , quantum sensing of magnetic fields 2 , electric fields 3 , or temperature 4 but also for nuclear magnetic resonance 5 or even to answer fundamental questions in physics 6,7 . The fabrication and reproducibility of scalable devices requires (and still lacks) sample homogeneity and creation yields of the qubits close to 100% 8 , but as well, the control and engineering of their environment 9 . The addressing using ion implantation provides high spatial resolution 10 , placement accuracy 11 , and even deterministic countable single ions 12–15 .…”

“…It is known that a large part of these vacancies are lost by recombination with carbon interstitials, by formation of di-vacancies or other complexes (vacancy chains, VH) or by diffusion to dislocations or to the diamond surface for the shallow ones. It was moreover shown that the proportion of vacancy complexes (with respect to isolated vacancies) increases with the atomic mass of the implanted ions 9 and that suitable thermal treatments enable the dissociation of vacancy chains 21 . Efforts were also made to increase the NV yield (for example by co-implantation of carbon 22 , post-irradiation with electrons or protons to produce additional vacancies 23,24 or more recently very efficiently by laser writing 25 ) and to understand the NV formation process 26,27 .…”

Can europium atoms form luminescent centres in diamond: A combined theoretical–experimental study

“…3,9 However, because diamond has a very large band gap this provides opportunities for the use of alternate optically active defects. [10][11][12] In this context, both the Si-and Ge-vacancy defect have received increased interest. [13][14][15][16][17] Within condensed matter science, rare-earth (RE) elements receive a lot of attention as optical dopants, as they give rise to very sharp emission lines, for a wide variety of wavelengths from UV to IR.…”

Window into NV center kinetics via repeated annealing and spatial tracking of thousands of individual NV centers

“…Both NV PL quenching as well as enhancement has been reported in the literature over a wide range of temperatures from 1100-1500 • C [38][39][40][41], with higher tem-perature quenching often attributed to NV migration to form larger complexes [41,42]. Due to short N migration length, complex formation can only explain quenching in high-N samples [25]. Our results indicate several factors may account for the observed variance in NV quenching: (1) Compositional sample variance with respect to hydrogen traps, (2) Simultaneous creation and quenching events with the specific annealing temperatures and times determining a net outcome in either direction and (3) the hydrogen content in the annealing furnace, suggested by our observed surface dependence of the depletion layer.…”