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DFT modeling of strained group-IV color centers in diamond

Thijs G. I. van Wijk, Esin Aylin Melan, Rani Mary Joy, Emerick Yves Guillaume, Paulius Pobedinskas, Ken Haenen, Danny E. P. Vanpoucke

Published Jan 1, 2026• 0 citations
OpenAlex

Abstract

Diamond color centers are considered as viable candidates for solid state qubits and single photon sources for quantum technological applications ranging from quantum sensing to quantum information processing [1]. Color centers are created through ion beam implantation or incorporation during chemical vapor deposition. This way most elements of the periodic table have been considered at some point in the past, even lanthanides like Eu, due to their sharp spectral properties [2]. However, in recent years, group-IV color centers have been gaining attention due to their excellent Debye-Waller factor, making them very suitable for optically based quantum applications. In such applications, a sharp and robust zero-phonon line (ZPL) are prime qualities sought after. Unfortunately, practical diamond based devices contain several sources of strain, originating from the ion beam implantation and annealing during device fabrication. This strain results in a shifting of the ZPL depending on the type of strain and magnitude experienced by the color center [3,4,5]. Using density functional theory (DFT) calculations, the impact of isotropic and anisotropic strain on the GeV and SnV centers in diamond is investigated, with the aim of understanding the experimentally observed distributions of ZPL positions. By using defect concentrations of 1.5% down to 0.1% (64-1000 atom conventional cells) we show that it is possible to extrapolate to experimentally relevant concentrations [3,4,5]. The calculated ZPL position and strain-induced shifts are presented for both neutral and negatively charged color centers. For the GeV 0 color center, both red and blue shifts are obtained for isotropic strain, while anisotropic strain only gives rise to a redshift. In case of the latter, the absolute magnitude of the shift is also significantly larger [3]. In case of the SnV 0 and SnV-, the position of the ZPL shows a smaller dependence on the color center concentration. In contrast, the ZPL shift for SnV centers is larger than the one obtained for the GeV 0 color center [4,5]. We also note that the impact of the charge state is rather non-trivial. The calculated results are discussed within the context of the experimental observation of distributions of ZPL positions for the SnV and GeV centers [3,4]. We highlight some of the pitfalls when comparing calculated and experimental results, and indicate how further experimental-theoretical studies can provide insights into the black box of experimentally doped samples [4,5].

Related papers

Straining Group-IV Vacancy Color Centers in Diamond: A DFT study of the ZPL position and shift

Thijs G. I. van Wijk, Esin Aylin Melan, Rani Mary Joy +4 more

Color centers play an important role in the development of diamond based devices, both for quantum technological applications as well as sensing applications. 1 Most elements of the periodic table have been considered as color center in diamond at some point in the past, even lanthanides like Eu, due to their sharp spectral properties. 2 Group-IV color centers have more recently gained attention due to their excellent Debye-Waller factor, making them very suitable for optically based quantum applications. However, practical diamond based devices contain several sources of strain, which result in a shifting of the zero-phonon line depending on the type of strain and magnitude experienced by the color center. 3,4 Using density functional theory calculations, we investigate the impact of isotropic and anisotropic strain on the GeV and SnV centers in diamond, with the aim of understanding the experimentally observed distributions of ZPL positions. Using defect concentrations of 1.5% down to 0.1% (64-1000 atom conventional cells) we show that it is possible to extrapolate to experimentally relevant concentrations. 3,4 The calculated ZPL position and strain-induced shifts are presented for both neutral and negatively charged color centers. For the GeV 0 color center, both red and blue shifts are obtained for isotropic strain, while anisotropic strain only gives rise to a redshift. In case of the latter, the absolute magnitude of the shift is also significantly larger. 3 In case of the SnV 0 and SnV-, the position of the ZPL shows a smaller dependence on the color center concentration. In contrast, the ZPL shift is larger than is obtained for the GeV 0 color center. We also note that the impact of the charge state is rather non-trivial. The calculated results are discussed within the context of the experimental observation of distributions of ZPL positions for the SnV and GeV centers. We highlight some of the pitfalls when comparing calculated and experimental results, and indicate how further experimental-theoretical studies can provide insights into the black box of experimentally doped samples.

•Jan 1, 2026•0 citations

Optimizing the Production of Single Color Centers in Diamond

Rodrick Kuate Defo, Efthimios Kaxiras, Steven L. Richardson

Experiments with the negatively charged nitrogen vacancy (N$V^-$) in diamond highlight this defect's promise for coherent storage of quantum information. They have also spurred investigations of other color centers in diamond formed by defects that consist of Group IV element (Si, Ge, Sn, Pb) and vacancies which have different atomic structure than the N$V^-$ center. To date, these other color centers have not exhibited coherence quite as impressive as that of the N$V^-$ center. Spectral diffusion and the low Debye-Waller factor are important limitations of the N$V^-$ center that make investigation of the other color centers necessary to advance the field. In this work we use density-functional theory (DFT) to study the thermodynamics and kinetics associated with the N$V$, Si$V$, Ge$V$, Sn$V$ and Pb$V$ color centers in diamond. We find agreement between our theoretical calculations and the charge state of various color centers as observed in intrinsic diamond. We determine the Fermi level values that enhance the production of isolated color centers, which may lead to longer coherence times than their present values.

arXiv:1905.10832•May 26, 2019•0 citations

Germanium-Vacancy Single Color Centers in Diamond

Takayuki Iwasaki, Fumitaka Ishibashi, Yoshiyuki Miyamoto +13 more

Atomic-sized fluorescent defects in diamond are widely recognized as a promising solid state platform for quantum cryptography and quantum information processing. For these applications, single photon sources with a high intensity and reproducible fabrication methods are required. In this study, we report a novel color center in diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV center, which has a sharp and strong photoluminescence band with a zero-phonon line at 602 nm at room temperature. We demonstrate this new color center works as a single photon source. Both ion implantation and chemical vapor deposition techniques enabled fabrication of GeV centers in diamond. A first-principles calculation revealed the atomic crystal structure and energy levels of the GeV center.

Scientific Reports•Aug 7, 2015•353 citations

Origin of structure and zero-phonon-line anomalies of XV centers in diamond (X=Si, Ge, Sn, Pb)

Chen Qiu, Hui‐Xiong Deng, Songyuan Geng +1 more

Color centers in diamonds have emerged as a promising candidate for quantum information and quantum computing applications. Compared to the well-known and widely studied nitrogen-vacancy ${\mathrm{N}}_{\mathrm{C}}\text{\ensuremath{-}}{\mathrm{V}}_{\mathrm{C}}$ (NV) color center with ${C}_{3v}$ symmetry, the group-IV vacancy color centers ${\mathrm{V}}_{\mathrm{C}}\text{\ensuremath{-}}X\text{\ensuremath{-}}{\mathrm{V}}_{\mathrm{C}}$ (XV, $X=\mathrm{Si}$, Ge, Sn, Pb), exhibit structures with the ${D}_{3d}$ symmetry, which give rise to more stable coherent optical transitions for the zero-phonon line (ZPL) due to its inversion symmetry. Moreover, it is experimentally found that the ZPL peak of XV centers increases from Si to Sn to Ge to Pb, i.e., it does not vary monotonically with the atomic numbers. So far, the physical origin of the unusual local structures and the abnormal trend of ZPL of the XV centers are not well understood. In this paper, based on density-functional theory calculations and symmetry analysis, we demonstrate that the large size of the X atoms plays a dominant role in moving the X atoms away from the substitution site to the bond-center site between the two carbon vacancies to form the ${D}_{3d}$ structure that can effectively reduce the local strain energy. Meanwhile, we find that the abnormal trends of ZPL of the XV centers derive from a competition of the $p\ensuremath{-}p$ coupling and $p\ensuremath{-}d$ coupling between X atoms and the divacancy based on the band-coupling mechanism. Our study, therefore, provides insights into the origin of the abnormal trends of ZPL and the local structure of XV centers in diamonds.

Physical review. B./Physical review. B•Jun 26, 2023•14 citations

Microscopic Insight into the Inhomogeneous Broadening of Zero-Phonon Lines of GeV– Color Centers in Chemical Vapor Deposition Diamond Films Synthesized from Gaseous Germane

Ivan Yu. Eremchev, Arthur Yu. Neliubov, Kirill N. Boldyrev +4 more

Diamonds with impurity color centers are a novel class of functional materials with potential for various photonics applications such as quantum optics, metrology, sensorics, and life sciences. When introducing defect centers, a broad range of questions arises about the nature of the photophysical processes in the new materials, in particular regarding the relationship between spectral and morphological properties. Here we present results of comprehensive spectroscopic studies on diamond films with germanium-vacancy (GeV – ) centers, synthesized by chemical vapor deposition from gaseous germane (GeH 4 ). The combination of different techniques (emission and fluorescence excitation spectroscopy, epi-microscopy, and nanoscopy up to the single-emitter level) at room and cryogenic temperatures has shed light onto the spatial distribution of the spectral properties of the GeV – centers in different microregions of the diamond crystal and its relation to local strain/stress. We demonstrate a clear correlation between inhomogeneous broadening and morphological heterogeneities of the sample. Ultranarrow (tens of MHz) stable zero-phonon lines have been observed, which are a prerequisite for various applications.

The Journal of Physical Chemistry C•Jul 30, 2021•18 citations

New insight into the spin-conserving excitation of the negatively charged nitrogen-vacancy center in diamond

Bei Deng, R. Q. Zhang, Xingqiang Shi

The negatively charged nitrogen-vacancy (N-V(-)) color center in diamond is an important solid-state single photon source for applications to quantum communication and distributed quantum computation. Its full usefulness relies on sufficient radiative emission of the optical photons which requires realizable control to enhance emission into the zero-phonon line (ZPL) but until now is still a challenge. Detailed understanding of the associated excitation process would be of essential importance for such objective. Here we report a theoretical work that probes the spin-conserving optical excitation of the N-V(-) center. Using density-functional-theory (DFT) calculations, we find that the ZPL and the phonon-side band (PSB) depend sensitively on the axial strain of the system. Besides, we find a relatively small PSB appearing at about 100 GPa in the emission spectrum at low temperatures, which provides a means to enhance the coherent emission of the N-V(-) center in quantum optical networks.

Scientific Reports•Jun 3, 2014•16 citations
Diamond color centers are considered as viable candidates for solid state qubits and single photon sources for quantum technological applications ranging from quantum sensing to quantum information processing [1]. Color centers are created through ion beam implantation or incorporation during chemical vapor deposition. This way most elements of the periodic table have been considered at some point in the past, even lanthanides like Eu, due to their sharp spectral properties [2]. However, in recent years, group-IV color centers have been gaining attention due to their excellent Debye-Waller factor, making them very suitable for optically based quantum applications. In such applications, a sharp and robust zero-phonon line (ZPL) are prime qualities sought after. Unfortunately, practical diamond based devices contain several sources of strain, originating from the ion beam implantation and annealing during device fabrication. This strain results in a shifting of the ZPL depending on the type of strain and magnitude experienced by the color center [3,4,5]. Using density functional theory (DFT) calculations, the impact of isotropic and anisotropic strain on the GeV and SnV centers in diamond is investigated, with the aim of understanding the experimentally observed distributions of ZPL positions. By using defect concentrations of 1.5% down to 0.1% (64-1000 atom conventional cells) we show that it is possible to extrapolate to experimentally relevant concentrations [3,4,5]. The calculated ZPL position and strain-induced shifts are presented for both neutral and negatively charged color centers. For the GeV 0 color center, both red and blue shifts are obtained for isotropic strain, while anisotropic strain only gives rise to a redshift. In case of the latter, the absolute magnitude of the shift is also significantly larger [3]. In case of the SnV 0 and SnV-, the position of the ZPL shows a smaller dependence on the color center concentration. In contrast, the ZPL shift for SnV centers is larger than the one obtained for the GeV 0 color center [4,5]. We also note that the impact of the charge state is rather non-trivial. The calculated results are discussed within the context of the experimental observation of distributions of ZPL positions for the SnV and GeV centers [3,4]. We highlight some of the pitfalls when comparing calculated and experimental results, and indicate how further experimental-theoretical studies can provide insights into the black box of experimentally doped samples [4,5].
Color centers play an important role in the development of diamond based devices, both for quantum technological applications as well as sensing applications. 1 Most elements of the periodic table have been considered as color center in diamond at some point in the past, even lanthanides like Eu, due to their sharp spectral properties. 2 Group-IV color centers have more recently gained attention due to their excellent Debye-Waller factor, making them very suitable for optically based quantum applications. However, practical diamond based devices contain several sources of strain, which result in a shifting of the zero-phonon line depending on the type of strain and magnitude experienced by the color center. 3,4 Using density functional theory calculations, we investigate the impact of isotropic and anisotropic strain on the GeV and SnV centers in diamond, with the aim of understanding the experimentally observed distributions of ZPL positions. Using defect concentrations of 1.5% down to 0.1% (64-1000 atom conventional cells) we show that it is possible to extrapolate to experimentally relevant concentrations. 3,4 The calculated ZPL position and strain-induced shifts are presented for both neutral and negatively charged color centers. For the GeV 0 color center, both red and blue shifts are obtained for isotropic strain, while anisotropic strain only gives rise to a redshift. In case of the latter, the absolute magnitude of the shift is also significantly larger. 3 In case of the SnV 0 and SnV-, the position of the ZPL shows a smaller dependence on the color center concentration. In contrast, the ZPL shift is larger than is obtained for the GeV 0 color center. We also note that the impact of the charge state is rather non-trivial. The calculated results are discussed within the context of the experimental observation of distributions of ZPL positions for the SnV and GeV centers. We highlight some of the pitfalls when comparing calculated and experimental results, and indicate how further experimental-theoretical studies can provide insights into the black box of experimentally doped samples.
Experiments with the negatively charged nitrogen vacancy (NV−V^-V−) in diamond highlight this defect's promise for coherent storage of quantum information. They have also spurred investigations of other color centers in diamond formed by defects that consist of Group IV element (Si, Ge, Sn, Pb) and vacancies which have different atomic structure than the NV−V^-V− center. To date, these other color centers have not exhibited coherence quite as impressive as that of the NV−V^-V− center. Spectral diffusion and the low Debye-Waller factor are important limitations of the NV−V^-V− center that make investigation of the other color centers necessary to advance the field. In this work we use density-functional theory (DFT) to study the thermodynamics and kinetics associated with the NVVV, SiVVV, GeVVV, SnVVV and PbVVV color centers in diamond. We find agreement between our theoretical calculations and the charge state of various color centers as observed in intrinsic diamond. We determine the Fermi level values that enhance the production of isolated color centers, which may lead to longer coherence times than their present values.
Atomic-sized fluorescent defects in diamond are widely recognized as a promising solid state platform for quantum cryptography and quantum information processing. For these applications, single photon sources with a high intensity and reproducible fabrication methods are required. In this study, we report a novel color center in diamond, composed of a germanium (Ge) and a vacancy (V) and named the GeV center, which has a sharp and strong photoluminescence band with a zero-phonon line at 602 nm at room temperature. We demonstrate this new color center works as a single photon source. Both ion implantation and chemical vapor deposition techniques enabled fabrication of GeV centers in diamond. A first-principles calculation revealed the atomic crystal structure and energy levels of the GeV center.
Color centers in diamonds have emerged as a promising candidate for quantum information and quantum computing applications. Compared to the well-known and widely studied nitrogen-vacancy ${\mathrm{N}}_{\mathrm{C}}\text{\ensuremath{-}}{\mathrm{V}}_{\mathrm{C}}$ (NV) color center with C3v{C}_{3v}C3v​ symmetry, the group-IV vacancy color centers ${\mathrm{V}}_{\mathrm{C}}\text{\ensuremath{-}}X\text{\ensuremath{-}}{\mathrm{V}}_{\mathrm{C}}$ (XV, X=SiX=\mathrm{Si}X=Si, Ge, Sn, Pb), exhibit structures with the D3d{D}_{3d}D3d​ symmetry, which give rise to more stable coherent optical transitions for the zero-phonon line (ZPL) due to its inversion symmetry. Moreover, it is experimentally found that the ZPL peak of XV centers increases from Si to Sn to Ge to Pb, i.e., it does not vary monotonically with the atomic numbers. So far, the physical origin of the unusual local structures and the abnormal trend of ZPL of the XV centers are not well understood. In this paper, based on density-functional theory calculations and symmetry analysis, we demonstrate that the large size of the X atoms plays a dominant role in moving the X atoms away from the substitution site to the bond-center site between the two carbon vacancies to form the D3d{D}_{3d}D3d​ structure that can effectively reduce the local strain energy. Meanwhile, we find that the abnormal trends of ZPL of the XV centers derive from a competition of the $p\ensuremath{-}p$ coupling and $p\ensuremath{-}d$ coupling between X atoms and the divacancy based on the band-coupling mechanism. Our study, therefore, provides insights into the origin of the abnormal trends of ZPL and the local structure of XV centers in diamonds.
Diamonds with impurity color centers are a novel class of functional materials with potential for various photonics applications such as quantum optics, metrology, sensorics, and life sciences. When introducing defect centers, a broad range of questions arises about the nature of the photophysical processes in the new materials, in particular regarding the relationship between spectral and morphological properties. Here we present results of comprehensive spectroscopic studies on diamond films with germanium-vacancy (GeV – ) centers, synthesized by chemical vapor deposition from gaseous germane (GeH 4 ). The combination of different techniques (emission and fluorescence excitation spectroscopy, epi-microscopy, and nanoscopy up to the single-emitter level) at room and cryogenic temperatures has shed light onto the spatial distribution of the spectral properties of the GeV – centers in different microregions of the diamond crystal and its relation to local strain/stress. We demonstrate a clear correlation between inhomogeneous broadening and morphological heterogeneities of the sample. Ultranarrow (tens of MHz) stable zero-phonon lines have been observed, which are a prerequisite for various applications.
The negatively charged nitrogen-vacancy (N-V(-)) color center in diamond is an important solid-state single photon source for applications to quantum communication and distributed quantum computation. Its full usefulness relies on sufficient radiative emission of the optical photons which requires realizable control to enhance emission into the zero-phonon line (ZPL) but until now is still a challenge. Detailed understanding of the associated excitation process would be of essential importance for such objective. Here we report a theoretical work that probes the spin-conserving optical excitation of the N-V(-) center. Using density-functional-theory (DFT) calculations, we find that the ZPL and the phonon-side band (PSB) depend sensitively on the axial strain of the system. Besides, we find a relatively small PSB appearing at about 100 GPa in the emission spectrum at low temperatures, which provides a means to enhance the coherent emission of the N-V(-) center in quantum optical networks.