Bhatia, Pia; Shin, Trey T.; Kavetsky, Kyril; Sailors, Benjamin N.; Siokos, George; Uy-Tioco, Alexandra Sofia; Keneipp, Rachael N.; Gusdorff, Jordan A.; Bassett, Lee C.; Drndić, Marija
In: Micron, vol. 189, pp. 103747, 2024.
@article{Bhatia2024,
title = {A tale of two transfers: characterizing polydimethylsiloxane viscoelastic stamping and heated poly bis-A carbonate transfer of hexagonal boron nitride},
author = {Pia Bhatia and Trey T. Shin and Kyril Kavetsky and Benjamin N. Sailors and George Siokos and Alexandra Sofia Uy-Tioco and Rachael N. Keneipp and Jordan A. Gusdorff and Lee C. Bassett and Marija Drndić},
url = {https://www.sciencedirect.com/science/article/pii/S0968432824001641#sec0080},
doi = {10.1016/j.micron.2024.103747},
year = {2024},
date = {2024-11-26},
urldate = {2024-11-26},
journal = {Micron},
volume = {189},
pages = {103747},
abstract = {Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.
Gusdorff, Jordan A.; Bhatia, Pia; Shin, Trey T.; Uy-Tioco, Alexandra Sofia; Sailors, Benjamin N.; Keneipp, Rachael N.; Drndić, Marija; Bassett, Lee C.
Correlated Structural and Optical Characterization of Hexagonal Boron Nitride Journal Article Forthcoming
In: arXiv:2411.14408, Forthcoming.
@article{Gusdorff2024,
title = {Correlated Structural and Optical Characterization of Hexagonal Boron Nitride},
author = {Jordan A. Gusdorff and Pia Bhatia and Trey T. Shin and Alexandra Sofia Uy-Tioco and Benjamin N. Sailors and Rachael N. Keneipp and Marija Drndić and Lee C. Bassett},
url = {https://arxiv.org/abs/2411.14408},
doi = {10.48550/arXiv.2411.14408},
year = {2024},
date = {2024-11-21},
urldate = {2024-11-21},
journal = {arXiv:2411.14408},
abstract = {Hexagonal boron nitride (hBN) hosts quantum emitters that exhibit single-photon emission and spin-dependent fluorescence at room temperature. These features make hBN a promising platform for quantum sensing and photonics. Despite many investigations of their optical properties, the emitters' chemical structure remains unclear, as does the role of contamination at surfaces and interfaces in forming the emitters or modifying their properties. We prepare hBN samples that are compatible with both confocal photoluminescence microscopy (PL) and transmission electron microscopy (TEM), and we use those techniques to investigate correlations between fluorescent emission, flake morphology, and surface residue. We find that the microscopy techniques themselves induce changes in hBN's optical activity and residue morphology: PL measurements induce photobleaching, whereas TEM measurements alter surface residue and emission characteristics. We also study the effects of common treatments — annealing and oxygen plasma cleaning — on the structure and optical activity of hBN. The results illustrate the power and importance of correlative studies to elucidate aspects of microscopic mechanisms that influence hBN's functionality as a host for quantum emitters and spin defects.},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
Hexagonal boron nitride (hBN) hosts quantum emitters that exhibit single-photon emission and spin-dependent fluorescence at room temperature. These features make hBN a promising platform for quantum sensing and photonics. Despite many investigations of their optical properties, the emitters' chemical structure remains unclear, as does the role of contamination at surfaces and interfaces in forming the emitters or modifying their properties. We prepare hBN samples that are compatible with both confocal photoluminescence microscopy (PL) and transmission electron microscopy (TEM), and we use those techniques to investigate correlations between fluorescent emission, flake morphology, and surface residue. We find that the microscopy techniques themselves induce changes in hBN's optical activity and residue morphology: PL measurements induce photobleaching, whereas TEM measurements alter surface residue and emission characteristics. We also study the effects of common treatments — annealing and oxygen plasma cleaning — on the structure and optical activity of hBN. The results illustrate the power and importance of correlative studies to elucidate aspects of microscopic mechanisms that influence hBN's functionality as a host for quantum emitters and spin defects.
Patel, Raj N.; Fishman, Rebecca E. K.; Huang, Tzu-Yung; Gusdorff, Jordan A.; Fehr, David A.; Hopper, David A.; Breitweiser, S. Alex; Porat, Benjamin; Flatté, Michael E.; Bassett, Lee C.
Room Temperature Dynamics of an Optically Addressable Single Spin in Hexagonal Boron Nitride Journal Article
In: Nano Letters, vol. 24, iss. 25, pp. 7623-7628, 2024.
@article{Patel2024,
title = {Room Temperature Dynamics of an Optically Addressable Single Spin in Hexagonal Boron Nitride},
author = {Raj N. Patel and Rebecca E. K. Fishman and Tzu-Yung Huang and Jordan A. Gusdorff and David A. Fehr and David A. Hopper and S. Alex Breitweiser and Benjamin Porat and Michael E. Flatté and Lee C. Bassett},
url = {https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.4c01333},
doi = {10.1021/acs.nanolett.4c01333},
year = {2024},
date = {2024-06-11},
urldate = {2024-06-11},
journal = {Nano Letters},
volume = {24},
issue = {25},
pages = {7623-7628},
abstract = {Hexagonal boron nitride (h-BN) hosts pure single-photon emitters that have shown evidence of optically detected electronic spin dynamics. However, the electrical and chemical structures of these optically addressable spins are unknown, and the nature of their spin-optical interactions remains mysterious. Here, we use time-domain optical and microwave experiments to characterize a single emitter in h-BN exhibiting room temperature optically detected magnetic resonance. Using dynamical simulations, we constrain and quantify transition rates in the model, and we design optical control protocols that optimize the signal-to-noise ratio for spin readout. This constitutes a necessary step toward quantum control of spin states in h-BN.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN) hosts pure single-photon emitters that have shown evidence of optically detected electronic spin dynamics. However, the electrical and chemical structures of these optically addressable spins are unknown, and the nature of their spin-optical interactions remains mysterious. Here, we use time-domain optical and microwave experiments to characterize a single emitter in h-BN exhibiting room temperature optically detected magnetic resonance. Using dynamical simulations, we constrain and quantify transition rates in the model, and we design optical control protocols that optimize the signal-to-noise ratio for spin readout. This constitutes a necessary step toward quantum control of spin states in h-BN.
Keneipp, Rachael N.; Gusdorff, Jordan A.; Bhatia, Pia; Shin, Trey T.; Bassett, Lee C.; Drndić, Marija
Nanoscale Sculpting of Hexagonal Boron Nitride with an Electron Beam Journal Article
In: Journal of Physical Chemistry C, vol. 128, no. 21, pp. 8741–8749, 2024.
@article{Keneipp2024,
title = {Nanoscale Sculpting of Hexagonal Boron Nitride with an Electron Beam},
author = {Rachael N. Keneipp and Jordan A. Gusdorff and Pia Bhatia and Trey T. Shin and Lee C. Bassett and Marija Drndić},
url = {https://pubs.acs.org/doi/full/10.1021/acs.jpcc.4c02038},
doi = {10.1021/acs.jpcc.4c02038},
year = {2024},
date = {2024-05-17},
journal = {Journal of Physical Chemistry C},
volume = {128},
number = {21},
pages = {8741–8749},
abstract = {Creating sub- to few-nanometer defects and nanopores in hexagonal boron nitride (hBN) opens opportunities for engineering quantum emitters and for nanofluidic and sensing applications. Using the electron beam in the aberration-corrected scanning transmission electron microscope, we demonstrate modification, thinning, and drilling of features in few-layer hBN membranes (∼5 to 20 nm-thick). The atomic composition is monitored with electron energy loss spectroscopy, which also facilitates drift correction. We report effects of electron beam energy and exposure times on defect size and structure. While previous studies focused on beam energies of ≤80 keV to avoid material damage, we show that drilling is favorable at a higher beam energy of 200 keV. The drilling rate at 200 keV is about 10 times larger than at 80 keV (∼1.2 vs 0.1 nm/min), and smaller pores are achievable with minimized damage to the surrounding material. Thinned hBN nanoscale features demonstrate enhanced emission via photoluminescence spectroscopy.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Creating sub- to few-nanometer defects and nanopores in hexagonal boron nitride (hBN) opens opportunities for engineering quantum emitters and for nanofluidic and sensing applications. Using the electron beam in the aberration-corrected scanning transmission electron microscope, we demonstrate modification, thinning, and drilling of features in few-layer hBN membranes (∼5 to 20 nm-thick). The atomic composition is monitored with electron energy loss spectroscopy, which also facilitates drift correction. We report effects of electron beam energy and exposure times on defect size and structure. While previous studies focused on beam energies of ≤80 keV to avoid material damage, we show that drilling is favorable at a higher beam energy of 200 keV. The drilling rate at 200 keV is about 10 times larger than at 80 keV (∼1.2 vs 0.1 nm/min), and smaller pores are achievable with minimized damage to the surrounding material. Thinned hBN nanoscale features demonstrate enhanced emission via photoluminescence spectroscopy.
Patel, Raj N.; Hopper, David A.; Gusdorff, Jordan A.; Turiansky, Mark E.; Huang, Tzu-Yung; Fishman, Rebecca E. K.; Porat, Benjamin; de Walle, Chris G. Van; Bassett, Lee C.
Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride Journal Article
In: PRX Quantum, vol. 3, no. 3, pp. 030331, 2022.
@article{Patel2022,
title = {Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride},
author = {Raj N. Patel and David A. Hopper and Jordan A. Gusdorff and Mark E. Turiansky and Tzu-Yung Huang and Rebecca E. K. Fishman and Benjamin Porat and Chris G. Van de Walle and Lee C. Bassett},
url = {https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.3.030331},
doi = {10.1103/PRXQuantum.3.030331},
year = {2022},
date = {2022-09-01},
journal = {PRX Quantum},
volume = {3},
number = {3},
pages = {030331},
abstract = {Hexagonal boron nitride is a van der Waals material that hosts visible-wavelength quantum emitters at room temperature. However, experimental identification of the quantum emitters’ electronic structure is lacking, and key details of their charge and spin properties remain unknown. Here, we probe the optical dynamics of quantum emitters in hexagonal boron nitride using photon emission correlation spectroscopy. Several quantum emitters exhibit ideal single-photon emission with noise-limited photon antibunching, g(2)(0)=0. The photoluminescence emission lineshapes are consistent with individual vibronic transitions. However, polarization-resolved excitation and emission suggests the role of multiple optical transitions, and photon emission correlation spectroscopy reveals complicated optical dynamics associated with excitation and relaxation through multiple electronic excited states. We compare the experimental results to quantitative optical dynamics simulations, develop electronic structure models that are consistent with the observations, and discuss the results in the context of ab initio theoretical calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride is a van der Waals material that hosts visible-wavelength quantum emitters at room temperature. However, experimental identification of the quantum emitters’ electronic structure is lacking, and key details of their charge and spin properties remain unknown. Here, we probe the optical dynamics of quantum emitters in hexagonal boron nitride using photon emission correlation spectroscopy. Several quantum emitters exhibit ideal single-photon emission with noise-limited photon antibunching, g(2)(0)=0. The photoluminescence emission lineshapes are consistent with individual vibronic transitions. However, polarization-resolved excitation and emission suggests the role of multiple optical transitions, and photon emission correlation spectroscopy reveals complicated optical dynamics associated with excitation and relaxation through multiple electronic excited states. We compare the experimental results to quantitative optical dynamics simulations, develop electronic structure models that are consistent with the observations, and discuss the results in the context of ab initio theoretical calculations.
Turiansky, M E; Alkauskas, A; Bassett, L C; de Walle, Van C G
Dangling bonds in hexagonal boron nitride as single-photon emitters Journal Article
In: Physical Review Letters, vol. 123, no. 12, pp. 127401, 2019, ISSN: 1079-7114.
@article{Turiansky2019,
title = {Dangling bonds in hexagonal boron nitride as single-photon emitters},
author = {M E Turiansky and A Alkauskas and L C Bassett and Van C G de Walle},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.127401},
doi = {10.1103},
issn = {1079-7114},
year = {2019},
date = {2019-09-16},
journal = {Physical Review Letters},
volume = {123},
number = {12},
pages = {127401},
abstract = {Hexagonal boron nitride has been found to host color centers that exhibit single-photon emission, but the microscopic origin of these emitters is unknown. We propose boron dangling bonds as the likely source of the observed single-photon emission around 2 eV. An optical transition where an electron is excited from a doubly occupied boron dangling bond to a localized B pz state gives rise to a zero-phonon line of 2.06 eV and emission with a Huang-Rhys factor of 2.3. This transition is linearly polarized with the absorptive and emissive dipole aligned. Because of the energetic position of the states within the band gap, indirect excitation through the conduction band will occur for sufficiently large excitation energies, leading to the misalignment of the absorptive and emissive dipoles seen in experiment. Our calculations predict a singlet ground state and the existence of a metastable triplet state, in agreement with experiment.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride has been found to host color centers that exhibit single-photon emission, but the microscopic origin of these emitters is unknown. We propose boron dangling bonds as the likely source of the observed single-photon emission around 2 eV. An optical transition where an electron is excited from a doubly occupied boron dangling bond to a localized B pz state gives rise to a zero-phonon line of 2.06 eV and emission with a Huang-Rhys factor of 2.3. This transition is linearly polarized with the absorptive and emissive dipole aligned. Because of the energetic position of the states within the band gap, indirect excitation through the conduction band will occur for sufficiently large excitation energies, leading to the misalignment of the absorptive and emissive dipoles seen in experiment. Our calculations predict a singlet ground state and the existence of a metastable triplet state, in agreement with experiment.
Exarhos, A L; Hopper, D A; Patel, R N; Doherty, M W; Bassett, L C
Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature Journal Article
In: Nature Communications, vol. 10, no. 222, 2019.
@article{Exarhos2019,
title = {Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature},
author = {A L Exarhos and D A Hopper and R N Patel and M W Doherty and L C Bassett},
url = {https://www.nature.com/articles/s41467-018-08185-8
https://www.nature.com/collections/rcdhyvxytb
https://spectrum.ieee.org/tech-talk/semiconductors/nanotechnology/qubits-and-nanosensors-in-a-2d-material
https://medium.com/penn-engineering/penn-engineers-develop-room-temperature-two-dimensional-platform-for-quantum-technology-cae3a5c0d8f9},
year = {2019},
date = {2019-01-15},
journal = {Nature Communications},
volume = {10},
number = {222},
abstract = {Selected as Editor's Highlight (linked)
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Selected as Editor's Highlight (linked)
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.
Exarhos, A L; Hopper, D A; Grote, R R; Alkauskas, A; Bassett, L C
Optical signatures of quantum emitters in suspended hexagonal boron nitride Journal Article
In: ACS Nano, vol. 11, pp. 3328-3336, 2017.
@article{Exarhos2017,
title = {Optical signatures of quantum emitters in suspended hexagonal boron nitride},
author = {A L Exarhos and D A Hopper and R R Grote and A Alkauskas and L C Bassett},
url = {https://pubs.acs.org/doi/abs/10.1021/acsnano.7b00665},
year = {2017},
date = {2017-03-07},
journal = {ACS Nano},
volume = {11},
pages = {3328-3336},
abstract = {Hexagonal boron nitride (h-BN) is rapidly emerging as an attractive material for solid-state quantum engineering. Analogously to three-dimensional wide-band-gap semiconductors such as diamond, h-BN hosts isolated defects exhibiting visible fluorescence at room temperature, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications is an understanding of the physics underlying h-BN’s quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects’ optical emission. Theoretical analysis of the defects’ spectra reveals similarities in vibronic coupling to h-BN phonon modes despite widely varying fluorescence wavelengths, and a statistical analysis of the polarized emission from many emitters throughout the same single-crystal flake uncovers a weak correlation between the optical dipole orientations of some defects and h-BN’s primitive crystallographic axes, despite a clear misalignment for other dipoles. These measurements constrain possible defect models and, moreover, suggest that several classes of emitters can exist simultaneously throughout free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN) is rapidly emerging as an attractive material for solid-state quantum engineering. Analogously to three-dimensional wide-band-gap semiconductors such as diamond, h-BN hosts isolated defects exhibiting visible fluorescence at room temperature, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications is an understanding of the physics underlying h-BN’s quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects’ optical emission. Theoretical analysis of the defects’ spectra reveals similarities in vibronic coupling to h-BN phonon modes despite widely varying fluorescence wavelengths, and a statistical analysis of the polarized emission from many emitters throughout the same single-crystal flake uncovers a weak correlation between the optical dipole orientations of some defects and h-BN’s primitive crystallographic axes, despite a clear misalignment for other dipoles. These measurements constrain possible defect models and, moreover, suggest that several classes of emitters can exist simultaneously throughout free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.
2024
Bhatia, Pia; Shin, Trey T.; Kavetsky, Kyril; Sailors, Benjamin N.; Siokos, George; Uy-Tioco, Alexandra Sofia; Keneipp, Rachael N.; Gusdorff, Jordan A.; Bassett, Lee C.; Drndić, Marija
In: Micron, vol. 189, pp. 103747, 2024.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, Materials Physics, nanocrystals
@article{Bhatia2024,
title = {A tale of two transfers: characterizing polydimethylsiloxane viscoelastic stamping and heated poly bis-A carbonate transfer of hexagonal boron nitride},
author = {Pia Bhatia and Trey T. Shin and Kyril Kavetsky and Benjamin N. Sailors and George Siokos and Alexandra Sofia Uy-Tioco and Rachael N. Keneipp and Jordan A. Gusdorff and Lee C. Bassett and Marija Drndić},
url = {https://www.sciencedirect.com/science/article/pii/S0968432824001641#sec0080},
doi = {10.1016/j.micron.2024.103747},
year = {2024},
date = {2024-11-26},
urldate = {2024-11-26},
journal = {Micron},
volume = {189},
pages = {103747},
abstract = {Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.},
keywords = {2-dimensional systems, Materials Physics, nanocrystals},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.
Patel, Raj N.; Fishman, Rebecca E. K.; Huang, Tzu-Yung; Gusdorff, Jordan A.; Fehr, David A.; Hopper, David A.; Breitweiser, S. Alex; Porat, Benjamin; Flatté, Michael E.; Bassett, Lee C.
Room Temperature Dynamics of an Optically Addressable Single Spin in Hexagonal Boron Nitride Journal Article
In: Nano Letters, vol. 24, iss. 25, pp. 7623-7628, 2024.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, First-principles calculations, photon emission correlation spectroscopy, photon statistics, point defects
@article{Patel2024,
title = {Room Temperature Dynamics of an Optically Addressable Single Spin in Hexagonal Boron Nitride},
author = {Raj N. Patel and Rebecca E. K. Fishman and Tzu-Yung Huang and Jordan A. Gusdorff and David A. Fehr and David A. Hopper and S. Alex Breitweiser and Benjamin Porat and Michael E. Flatté and Lee C. Bassett},
url = {https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.4c01333},
doi = {10.1021/acs.nanolett.4c01333},
year = {2024},
date = {2024-06-11},
urldate = {2024-06-11},
journal = {Nano Letters},
volume = {24},
issue = {25},
pages = {7623-7628},
abstract = {Hexagonal boron nitride (h-BN) hosts pure single-photon emitters that have shown evidence of optically detected electronic spin dynamics. However, the electrical and chemical structures of these optically addressable spins are unknown, and the nature of their spin-optical interactions remains mysterious. Here, we use time-domain optical and microwave experiments to characterize a single emitter in h-BN exhibiting room temperature optically detected magnetic resonance. Using dynamical simulations, we constrain and quantify transition rates in the model, and we design optical control protocols that optimize the signal-to-noise ratio for spin readout. This constitutes a necessary step toward quantum control of spin states in h-BN.},
keywords = {2-dimensional systems, First-principles calculations, photon emission correlation spectroscopy, photon statistics, point defects},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN) hosts pure single-photon emitters that have shown evidence of optically detected electronic spin dynamics. However, the electrical and chemical structures of these optically addressable spins are unknown, and the nature of their spin-optical interactions remains mysterious. Here, we use time-domain optical and microwave experiments to characterize a single emitter in h-BN exhibiting room temperature optically detected magnetic resonance. Using dynamical simulations, we constrain and quantify transition rates in the model, and we design optical control protocols that optimize the signal-to-noise ratio for spin readout. This constitutes a necessary step toward quantum control of spin states in h-BN.
Keneipp, Rachael N.; Gusdorff, Jordan A.; Bhatia, Pia; Shin, Trey T.; Bassett, Lee C.; Drndić, Marija
Nanoscale Sculpting of Hexagonal Boron Nitride with an Electron Beam Journal Article
In: Journal of Physical Chemistry C, vol. 128, no. 21, pp. 8741–8749, 2024.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, color centers, photoluminescence, point defects
@article{Keneipp2024,
title = {Nanoscale Sculpting of Hexagonal Boron Nitride with an Electron Beam},
author = {Rachael N. Keneipp and Jordan A. Gusdorff and Pia Bhatia and Trey T. Shin and Lee C. Bassett and Marija Drndić},
url = {https://pubs.acs.org/doi/full/10.1021/acs.jpcc.4c02038},
doi = {10.1021/acs.jpcc.4c02038},
year = {2024},
date = {2024-05-17},
journal = {Journal of Physical Chemistry C},
volume = {128},
number = {21},
pages = {8741–8749},
abstract = {Creating sub- to few-nanometer defects and nanopores in hexagonal boron nitride (hBN) opens opportunities for engineering quantum emitters and for nanofluidic and sensing applications. Using the electron beam in the aberration-corrected scanning transmission electron microscope, we demonstrate modification, thinning, and drilling of features in few-layer hBN membranes (∼5 to 20 nm-thick). The atomic composition is monitored with electron energy loss spectroscopy, which also facilitates drift correction. We report effects of electron beam energy and exposure times on defect size and structure. While previous studies focused on beam energies of ≤80 keV to avoid material damage, we show that drilling is favorable at a higher beam energy of 200 keV. The drilling rate at 200 keV is about 10 times larger than at 80 keV (∼1.2 vs 0.1 nm/min), and smaller pores are achievable with minimized damage to the surrounding material. Thinned hBN nanoscale features demonstrate enhanced emission via photoluminescence spectroscopy.},
keywords = {2-dimensional systems, color centers, photoluminescence, point defects},
pubstate = {published},
tppubtype = {article}
}
Creating sub- to few-nanometer defects and nanopores in hexagonal boron nitride (hBN) opens opportunities for engineering quantum emitters and for nanofluidic and sensing applications. Using the electron beam in the aberration-corrected scanning transmission electron microscope, we demonstrate modification, thinning, and drilling of features in few-layer hBN membranes (∼5 to 20 nm-thick). The atomic composition is monitored with electron energy loss spectroscopy, which also facilitates drift correction. We report effects of electron beam energy and exposure times on defect size and structure. While previous studies focused on beam energies of ≤80 keV to avoid material damage, we show that drilling is favorable at a higher beam energy of 200 keV. The drilling rate at 200 keV is about 10 times larger than at 80 keV (∼1.2 vs 0.1 nm/min), and smaller pores are achievable with minimized damage to the surrounding material. Thinned hBN nanoscale features demonstrate enhanced emission via photoluminescence spectroscopy.
2022
Patel, Raj N.; Hopper, David A.; Gusdorff, Jordan A.; Turiansky, Mark E.; Huang, Tzu-Yung; Fishman, Rebecca E. K.; Porat, Benjamin; de Walle, Chris G. Van; Bassett, Lee C.
Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride Journal Article
In: PRX Quantum, vol. 3, no. 3, pp. 030331, 2022.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, color centers, photon emission correlation spectroscopy, photon statistics, point defects, quantum optics, single-photon sources
@article{Patel2022,
title = {Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride},
author = {Raj N. Patel and David A. Hopper and Jordan A. Gusdorff and Mark E. Turiansky and Tzu-Yung Huang and Rebecca E. K. Fishman and Benjamin Porat and Chris G. Van de Walle and Lee C. Bassett},
url = {https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.3.030331},
doi = {10.1103/PRXQuantum.3.030331},
year = {2022},
date = {2022-09-01},
journal = {PRX Quantum},
volume = {3},
number = {3},
pages = {030331},
abstract = {Hexagonal boron nitride is a van der Waals material that hosts visible-wavelength quantum emitters at room temperature. However, experimental identification of the quantum emitters’ electronic structure is lacking, and key details of their charge and spin properties remain unknown. Here, we probe the optical dynamics of quantum emitters in hexagonal boron nitride using photon emission correlation spectroscopy. Several quantum emitters exhibit ideal single-photon emission with noise-limited photon antibunching, g(2)(0)=0. The photoluminescence emission lineshapes are consistent with individual vibronic transitions. However, polarization-resolved excitation and emission suggests the role of multiple optical transitions, and photon emission correlation spectroscopy reveals complicated optical dynamics associated with excitation and relaxation through multiple electronic excited states. We compare the experimental results to quantitative optical dynamics simulations, develop electronic structure models that are consistent with the observations, and discuss the results in the context of ab initio theoretical calculations.},
keywords = {2-dimensional systems, color centers, photon emission correlation spectroscopy, photon statistics, point defects, quantum optics, single-photon sources},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride is a van der Waals material that hosts visible-wavelength quantum emitters at room temperature. However, experimental identification of the quantum emitters’ electronic structure is lacking, and key details of their charge and spin properties remain unknown. Here, we probe the optical dynamics of quantum emitters in hexagonal boron nitride using photon emission correlation spectroscopy. Several quantum emitters exhibit ideal single-photon emission with noise-limited photon antibunching, g(2)(0)=0. The photoluminescence emission lineshapes are consistent with individual vibronic transitions. However, polarization-resolved excitation and emission suggests the role of multiple optical transitions, and photon emission correlation spectroscopy reveals complicated optical dynamics associated with excitation and relaxation through multiple electronic excited states. We compare the experimental results to quantitative optical dynamics simulations, develop electronic structure models that are consistent with the observations, and discuss the results in the context of ab initio theoretical calculations.
2019
Turiansky, M E; Alkauskas, A; Bassett, L C; de Walle, Van C G
Dangling bonds in hexagonal boron nitride as single-photon emitters Journal Article
In: Physical Review Letters, vol. 123, no. 12, pp. 127401, 2019, ISSN: 1079-7114.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, Condensed Matter, First-principles calculations, Optical absorption spectroscopy, Optical microcavities, optical sources, point defects, Quantum wells, Semiconductor compounds
@article{Turiansky2019,
title = {Dangling bonds in hexagonal boron nitride as single-photon emitters},
author = {M E Turiansky and A Alkauskas and L C Bassett and Van C G de Walle},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.127401},
doi = {10.1103},
issn = {1079-7114},
year = {2019},
date = {2019-09-16},
journal = {Physical Review Letters},
volume = {123},
number = {12},
pages = {127401},
abstract = {Hexagonal boron nitride has been found to host color centers that exhibit single-photon emission, but the microscopic origin of these emitters is unknown. We propose boron dangling bonds as the likely source of the observed single-photon emission around 2 eV. An optical transition where an electron is excited from a doubly occupied boron dangling bond to a localized B pz state gives rise to a zero-phonon line of 2.06 eV and emission with a Huang-Rhys factor of 2.3. This transition is linearly polarized with the absorptive and emissive dipole aligned. Because of the energetic position of the states within the band gap, indirect excitation through the conduction band will occur for sufficiently large excitation energies, leading to the misalignment of the absorptive and emissive dipoles seen in experiment. Our calculations predict a singlet ground state and the existence of a metastable triplet state, in agreement with experiment.},
keywords = {2-dimensional systems, Condensed Matter, First-principles calculations, Optical absorption spectroscopy, Optical microcavities, optical sources, point defects, Quantum wells, Semiconductor compounds},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride has been found to host color centers that exhibit single-photon emission, but the microscopic origin of these emitters is unknown. We propose boron dangling bonds as the likely source of the observed single-photon emission around 2 eV. An optical transition where an electron is excited from a doubly occupied boron dangling bond to a localized B pz state gives rise to a zero-phonon line of 2.06 eV and emission with a Huang-Rhys factor of 2.3. This transition is linearly polarized with the absorptive and emissive dipole aligned. Because of the energetic position of the states within the band gap, indirect excitation through the conduction band will occur for sufficiently large excitation energies, leading to the misalignment of the absorptive and emissive dipoles seen in experiment. Our calculations predict a singlet ground state and the existence of a metastable triplet state, in agreement with experiment.
Exarhos, A L; Hopper, D A; Patel, R N; Doherty, M W; Bassett, L C
Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature Journal Article
In: Nature Communications, vol. 10, no. 222, 2019.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, point defects
@article{Exarhos2019,
title = {Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature},
author = {A L Exarhos and D A Hopper and R N Patel and M W Doherty and L C Bassett},
url = {https://www.nature.com/articles/s41467-018-08185-8
https://www.nature.com/collections/rcdhyvxytb
https://spectrum.ieee.org/tech-talk/semiconductors/nanotechnology/qubits-and-nanosensors-in-a-2d-material
https://medium.com/penn-engineering/penn-engineers-develop-room-temperature-two-dimensional-platform-for-quantum-technology-cae3a5c0d8f9},
year = {2019},
date = {2019-01-15},
journal = {Nature Communications},
volume = {10},
number = {222},
abstract = {Selected as Editor's Highlight (linked)
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.},
keywords = {2-dimensional systems, point defects},
pubstate = {published},
tppubtype = {article}
}
Selected as Editor's Highlight (linked)
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.
Press coverage in IEEE Spectrum and Penn Medium (linked)
Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.
2017
Exarhos, A L; Hopper, D A; Grote, R R; Alkauskas, A; Bassett, L C
Optical signatures of quantum emitters in suspended hexagonal boron nitride Journal Article
In: ACS Nano, vol. 11, pp. 3328-3336, 2017.
Abstract | Links | BibTeX | Tags: 2-dimensional systems, Condensed Matter, optical sources, point defects
@article{Exarhos2017,
title = {Optical signatures of quantum emitters in suspended hexagonal boron nitride},
author = {A L Exarhos and D A Hopper and R R Grote and A Alkauskas and L C Bassett},
url = {https://pubs.acs.org/doi/abs/10.1021/acsnano.7b00665},
year = {2017},
date = {2017-03-07},
journal = {ACS Nano},
volume = {11},
pages = {3328-3336},
abstract = {Hexagonal boron nitride (h-BN) is rapidly emerging as an attractive material for solid-state quantum engineering. Analogously to three-dimensional wide-band-gap semiconductors such as diamond, h-BN hosts isolated defects exhibiting visible fluorescence at room temperature, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications is an understanding of the physics underlying h-BN’s quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects’ optical emission. Theoretical analysis of the defects’ spectra reveals similarities in vibronic coupling to h-BN phonon modes despite widely varying fluorescence wavelengths, and a statistical analysis of the polarized emission from many emitters throughout the same single-crystal flake uncovers a weak correlation between the optical dipole orientations of some defects and h-BN’s primitive crystallographic axes, despite a clear misalignment for other dipoles. These measurements constrain possible defect models and, moreover, suggest that several classes of emitters can exist simultaneously throughout free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.},
keywords = {2-dimensional systems, Condensed Matter, optical sources, point defects},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN) is rapidly emerging as an attractive material for solid-state quantum engineering. Analogously to three-dimensional wide-band-gap semiconductors such as diamond, h-BN hosts isolated defects exhibiting visible fluorescence at room temperature, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications is an understanding of the physics underlying h-BN’s quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects’ optical emission. Theoretical analysis of the defects’ spectra reveals similarities in vibronic coupling to h-BN phonon modes despite widely varying fluorescence wavelengths, and a statistical analysis of the polarized emission from many emitters throughout the same single-crystal flake uncovers a weak correlation between the optical dipole orientations of some defects and h-BN’s primitive crystallographic axes, despite a clear misalignment for other dipoles. These measurements constrain possible defect models and, moreover, suggest that several classes of emitters can exist simultaneously throughout free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.
Select publications before 2014
- “All-optical control of a solid-state spin using coherent dark states”, C. G. Yale, B. B. Buckley, D. J. Christle, G. Burkard, F. J. Heremans, L. C. Bassett, and D. D. Awschalom, Proc. Natl. Acad. Sci. USA 110, 7595 (2013).
- “Quantum spintronics: Engineering and manipulating atom-like spins in semiconductors”, D.D. Awschalom, L.C. Bassett, A.S. Dzurak, E.L. Hu and J.R. Petta, Science 339, 1174 (2013).
Related article: “The Future of Quantum Information Processing”, J. Stajic, Science 339, 1163 (2013).
- “Engineering and quantum control of single spins in semiconductors”, D.M. Toyli, L.C. Bassett, B.B. Buckley, G. Calusine and D.D. Awschalom, MRS Bulletin 38, 139 (2013).
- “Engineering shallow spins in diamond with nitrogen delta-doping”, K. Ohno, F. J. Heremans, L. C. Bassett, B. A. Myers, D. M. Toyli, A. C. Bleszynski-Jayich, C. J. Palmstrøm, and D. D. Awschalom, Appl. Phys. Lett. 101, 082413 (2012).
- “Electrical tuning of single nitrogen-vacancy center optical transitions enhanced by photoinduced fields”, L. C. Bassett, F. J. Heremans, C. G. Yale, B. B. Buckley, and D. D. Awschalom, Phys. Rev. Lett. 107, 266403 (2011).
- “Spin-light coherence for single-spin measurement and control in diamond”, B. B. Buckley, G. D. Fuchs, L. C. Bassett, and D. D. Awschalom, Science 330, 1212 (2010).
Related article: “Quantum measurement and control of single spins in diamond”, Science 330, 1188 (2010).