Electron confinement induced by diluted hydrogen-like ad-atoms in graphene ribbons

González, Jorge Méndez; Rosales, Luis; Pacheco, M.; Ayuela, Andrés

doi:10.1039/c5cp03061g

Cited by 9 publications

(7 citation statements)

References 80 publications

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“…2 , and τ 3 are decay time values for exponential components. The decay times (τ 1 , τ 2 , and τ 3 ) with their respective percentage contributions of the different color components, viz., 375, 410, 460, 490, 530, 560, 610, 720, 780, and 850 nm, are given in Supporting Information Table1.…”

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confidence: 99%

An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

et al. 2016

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The present work describes various defects-induced tunable emission behavior of MgAl2O4 compounds obtained after annealing at different temperatures through a sol–gel combustion route. Multiple defect centers, such as F, F2, F+, and F2 2+ and different shallow and deep defects were found to be present inside the band gap, as confirmed by the lifetime and time-resolved emission spectroscopy (TRES) studies. The tunable emission characteristic at different annealing temperatures could be linked with the phase behavior of the spinel. Excitation wavelength variation suggested that a photoconversion process of F to F+ centers was involved with λex = 250 nm, followed by a trapping–de-trapping mechanism of the released electrons within different trap states. An exchange mechanism of electrons in between conduction band and shallow states was also observed at room temperature, which was absent at low temperature, as indicated by the emission profile. These observations render it to be a potential optical-based thermal sensor material. DFT-based calculations were carried out for both pure and various oxygen-vacancy-introduced spinel phases in order to characterize the different defect states inside the band gap. Finally, on the basis of theoretical and experimental results, a model has been proposed to explain the mechanisms related to emission tunability.

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An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

et al. 2016

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“…In the GF approach the TB Hamiltonian describing the SWNT lattice and hydrogen adatoms is then used to calculate the LDOS of the central QD (for details see Appendix C). Within some approximation, adatoms can be considered equivalent to vacancies, [57][58][59][60][61] and this is how they are modelled in the ED approach, setting the on-site energy at the defects to ε i = 200 eV. The full TB Hamiltonian of the isolated SWNT lattice with vacancies in the ED approach is then diagonalized numerically, 62 providing directly the eigenstate wave functions.…”

Section: B Theoretical Interpretationmentioning

confidence: 99%

Metallic carbon nanotube quantum dots with broken symmetries as a platform for tunable terahertz detection

Buchs

Margańska

González

et al. 2021

Applied Physics Reviews

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Generating and detecting radiation in the technologically relevant range of the so-called terahertz gap (0.1 − 10 THz) is challenging because of a lack of efficient sources and detectors. Quantum dots in carbon nanotubes have shown great potential to build sensitive terahertz detectors usually based on photon-assisted tunnelling. A recently reported mechanism combining resonant quantum dot transitions and tunnelling barriers asymmetries results in a narrow linewidth photocurrent response with a large signal-to-noise ratio under weak THz radiation. That device was sensitive to one frequency, corresponding to transitions between equidistant quantized states. In this work we show, using numerical together with scanning tunnelling spectroscopy studies of a defect-induced metallic zigzag single-walled carbon nanotube quantum dot that simultaneously breaking various symmetries in metallic nanotube quantum dots of arbitrary chirality strongly relaxes the selection rules in the electric dipole approximation, and removes energy degeneracies. This leads to a richer set of allowed optical transitions spanning frequencies from 1 THz to several tens of THz, for a ∼10 nm quantum dot. Based on these findings, we propose a terahertz detector device based on a metallic single-walled carbon nanotube quantum dot defined by artificial defects. Depending on its length and contacts transparency, the operating regimes range from a high-resolution gate-tunable terahertz sensor to a broadband terahertz detector. Our calculations indicate that the device is largely unaffected by temperatures up to 100 K, making carbon nanotube quantum dots with broken symmetries a promising platform to design tunable terahertz detectors that could operate at liquid nitrogen temperatures.

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“…In the GF approach the TB Hamiltonian describing the SWNT lattice and hydrogen adatoms is then used to calculate the LDOS of the central QD (for details see Appendix C 3). Within some approximation, adatoms can be considered equivalent to vacancies, [57][58][59][60][61] and this is how they are modelled in the ED approach, setting the on-site energy at the defects to ε i = 200 eV. The full TB Hamiltonian of the isolated SWNT lattice with vacancies in the ED approach is then diagonalized numerically, 62 providing directly the eigenstate wave functions.…”

Section: B Theoretical Interpretationmentioning

confidence: 99%

Metallic Carbon Nanotube Quantum Dots with Broken Symmetries as a Platform for Tunable Terahertz Detection

Buchs,

Marganska,

González

et al. 2020

Preprint

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Quantum dots (QD) in metallic single-walled carbon nanotubes (SWNT) have shown great potential to build sensitive terahertz (THz) detection devices usually based on photon-assisted tunneling. A recently reported mechanism based on a combination of resonant QD transitions and asymmetries in the tunneling barriers results in narrow linewidth photocurrent response with a large signal to noise ratio under weak THz radiation. However in such devices, due to metallic SWNTs linear dispersion relation, the detection range is intrinsically limited to allowed energy transitions between equidistant quantized states set by the QD length. Here, we show that simultaneously breaking translational, rotational and mirror symmetries in metallic SWNT QDs leads to a quantized spectrum with non-equidistant energy levels. This result stems from tight-binding and first-principle simulations of a defect-induced metallic zigzag SWNT QD and is validated experimentally by scanning tunneling spectroscopy studies. Importantly, we show that breaking symmetries in metallic SWNT QDs of arbitrary chirality strongly relaxes the selection rules in the electric dipole approximation, leading to a richer set of allowed optical transitions spanning frequencies from as low as 1 THz up to several tens of THz for a ∼10 nm QD. Such findings make metallic carbon nanotube QDs with broken symmetries a promising platform to design tunable THz detectors operating above liquid helium temperatures. In this context, we propose a device design based on a metallic SWNT QD engineered with artificially created defects.

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Electron confinement induced by diluted hydrogen-like ad-atoms in graphene ribbons

Cited by 9 publications

References 80 publications

An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

Metallic carbon nanotube quantum dots with broken symmetries as a platform for tunable terahertz detection

Metallic Carbon Nanotube Quantum Dots with Broken Symmetries as a Platform for Tunable Terahertz Detection

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Electron confinement induced by diluted hydrogen-like ad-atoms in graphene ribbons

Cited by 9 publications

References 80 publications

An Insight into the Various Defects-Induced Emission in MgAl2O4 and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

An Insight into the Various Defects-Induced Emission in MgAl2O4 and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

Metallic carbon nanotube quantum dots with broken symmetries as a platform for tunable terahertz detection

Metallic Carbon Nanotube Quantum Dots with Broken Symmetries as a Platform for Tunable Terahertz Detection

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An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

An Insight into the Various Defects-Induced Emission in MgAl₂O₄ and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach