KU Leuven

PhD in Physics at KU Leuven on “Quantum Color Centers in Diamond: Unraveling the Link Between the Atomic-scale Structure and Functionality”

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KU Leuven is an autonomous university. It was founded in 1425. It was born of and has grown within the Catholic tradition.

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(ref. BAP-2022-312)

You will be part of the division for Quantum Solid-State Physics (QSP) at the department of Physics and Astronomy of the KU Leuven (https://fys.kuleuven.be/qsp). KU Leuven, established in 1425, ranks number 42 on the Times Higher Education list. Moreover, according to the Reuters ranking, it is the seventh most innovative university worldwide (number one in Europe, after six American universities). You will join several other postdoctoral researchers, PhD students, master students and staff carrying out experimental research on condensed matter physics. Besides working in the state-of-the-art laboratories in Leuven, you will perform radiotracer experiments at the ISOLDE facility in CERN, Geneva. This PhD research will be performed in close collaboration with the University of Lisbon (PT), the University of Turin (IT) and the University of Hasselt (BE).

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During the last two decades, point defects in diamond – also referred to as color centers– have arisen as excellent building blocks for a wide variety of solid-state quantum devices and quantum technologies. Indeed, it has been shown that various defects can be introduced, which show bright single-photon emission at room temperature. So far, the negatively charged NV- defect, consisting of a single nitrogen impurity neighbored by a vacancy, has been the most widely studied candidate. Despite a number of particular advantages of the NV- center, the long fluorescent lifetime and a weak emission of theNV- into the zero-phonon line (ZPL) set an upper limit to the achievable photon rates of the quantum devices.

As a result, there has recently been a major effort in identifying alternative color centers and investigating their optical properties for applications where high photon counts are required. A specific class of centers that show very promising properties are the so-called group IV defects, i.e., the silicon-vacancy (SiV), germanium-vacancy (GeV), tin-vacancy (SnV) andlead-vacancy (PbV). Unlike the NV centers, they exhibit strong, narrow band emission into the ZPL and limited spectral diffusion, which has been assigned to the D3d symmetric configuration of the defect structure.

In nearly all cases, ion implantation is the key methodology either to introduce the impurity ina very controlled way, or to activate existing impurities via the introduction of vacancies. The advantages of implantation are multiple, e.g., excellent control of the impurity position and of the concentration, fully compatible with technological processing, etc. At the same time, the collision cascade resulting from the implantation process delivers the required vacancies to form the color centers. Whereas the NV center consists of a substitutional nitrogen atom with a neighboring carbon vacancy, the group IV vacancy centers are generally believed to exhibit a “split-vacancy” configuration, where the impurity resides at the middle of two C positions (bond-centered site), with the vacancy “split” over the two adjacent C sites. This configuration was initially suggested from abinitio calculations and confirmed indirectly from (magneto-)optical spectroscopic measurements, although thus far not experimentally proven. 

Our unique approach based on emission channeling (alattice location technique of unprecedented sensitivity) combined with photoluminescence enables us to unambiguously identify the atomic defect structure and provide a direct link to specific PLlines via radio tracer photoluminescence experiments. The lattice location studies will be performed at the ISOLDE facility at CERN, making use of radioactive probe atoms. On the one hand, based on the an isotropic emission of b particles upon decay of these implanted radioactive isotopes, we can identify and quantify the lattice site, even for extremely low fluences. Using this approach, we recently demonstrated a proof-of-principle of identifying and quantifying the split-vacancy SnV configuration in diamond. On the other hand, during the decay, the specific isotope transforms to a daughter nucleus. Consequently, the decay or growth of the corresponding PL lines enables to distinguish between luminescence originating from specific elements or specific defect configurations. These experiments using radioactive isotopes will be complemented with detailed investigations on stable isotopes, using the ion implantation and PL setups in Leuven.

Based on the outcome of this PhD project, we expect to be able to provide the fundamental understanding in these color centers, required to further enhance their efficiency.

Specifically, the aim of this PhD research is to:

  • Determine the exact lattice site(s) of a series of impurities (group IV and others) in diamond, both after implantation and upon thermal annealing. Using emission channeling, you will be able to investigate the low concentration regime that is relevant for single photon emission.
  • Investigate the photo luminescence (position, intensity, line width…) of the color centers,both on stable ions and on radio tracers.
  • Intimately link the specific PL lines to the respective configurations, and study how these can be tuned by optimizing the implantation and annealing conditions. This will allow you to unravel the formation efficiency of color centers in diamond, as well as the conditions required for narrow line emission.
  • Investigate correlations between particular defect configurations and the spin dephasing and decoherence time, using Ramsey and Hahn echo pulse sequencing.


  • We are looking for a highly driven candidate, motivated to work in an international research team.
  • Candidates must hold a Master’s degree in Physics, Engineering or Nanotechnology, with a strong background in solid-state physics and quantum physics.
  • Proficiency in the English language is also required, as well as good communication skills, both oral and written.


We offer a full-time, 4-year PhD student position, in a dynamic scientific environment, ata top international university.


For more information please contact Prof. dr. André Vantomme, tel.: +32 16 32 75 14, mail: andre.vantomme@kuleuven.be

You can apply for this job no later than June 16, 2022 via the online application tool

KU Leuven seeks to foster an environment where all talents can flourish, regardless of gender, age, cultural background, nationality or impairments. If you have any questions relating to accessibility or support, please contact us at diversiteit.HR@kuleuven.be.

Informatie over de vacature

PhD in Physics at KU Leuven on “Quantum Color Centers in Diamond: Unraveling the Link Between the Atomic-scale Structure and Functionality”
Oude Markt 13 Leuven, België
Uiterste sollicitatiedatum
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Over de werkgever

KU Leuven is an autonomous university. It was founded in 1425. It was born of and has grown within the Catholic tradition.

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