Quantum confinement effects on optical transitions in nanodiamonds containing nitrogen vacancies

Abstract

Colored nitrogen-vacancy (NV) centers in nanosize diamonds (d∼5 nm) are promising probe materials, because their optical transitions are sensitive to mechanical, vibrational and spin changes in the surroundings. Here, a linear response time-dependent density functional theory approach is used to describe the optical transitions in several NV-doped diamond quantum dots (QDs) in order to investigate size effects on the absorption spectra. By computing the full optical spectrum up to band-to-band transitions, we analyze both the localized "pinned" mid-gap and the charge-transfer excitations for an isolated reduced NV center. Sub-band charge-transfer excitations are shown to be size dependent, involving the excitation of the dopant sp 3 electrons to the diamond conduction band. Additionally, the NV-doped systems exhibit characteristic sp 3 − sp 3 excitations whose experimental energies are reproduced well and do not depend on QD size. However, the NV position and global cluster symmetry can affect the amount of the energy splitting of the vertical excitation energies of the mid-gap transitions.

Electronic structures and spectroscopic signatures of silicon-vacancy containing nanodiamonds

“…14 Doping introduces new subband-gap levels, and it has been shown that NV centers in diamond give rise to new dopant-centered sp 3 − sp 3 mid-gap electronic transitions and charge-transfer (CT or "photoionization") excited states. 22 Similar applications in quantum information processing 23 have been shown for the negatively-charged silicon-vacancy (SiV − ) center due to its short fluorescent lifetime, narrow emission line-width, and high percentage of photons (∼70-80%) emitted through its zero-phonon line (ZPL). 24,25 This defect has also been shown to be useful as a high-resolution high-pressure sensor.…”

“…They were constructed using the bulk face-centered cubic lattice parameter 7 a 0 = 0.357 nm and hydrogen atoms were used to passivate the surface dangling bonds, according to the procedure presented in Ref. 22. The sizes of these quantum dots are similar to the smallest nano-diamonds obtainable by detonation or laser-heated diamond anvil cell synthesis.…”

“…In this paper, theoretical investigations with a finite cluster approach of both the electronic and vibrational properties are carried out using hybrid density functional theory (DFT) and linear-response time-dependent density functional theory (LR-TDDFT) for a reduced SiV − color center in nanodiamond systems of different sizes. TDDFT, combined with a cluster approach, has shown very promising results for the theoretical characterization of excited states in doped semi-conductor quantum dots (in particular, NV doped nanodiamonds) 22,[39][40][41][42][43][44][45][46][47][48] and the vibrational/dynamical properties of molecules. [49][50][51][52][53] The work presented herein focuses on the quantum confinement effects on the electronic (UV-Vis and X-ray) and vibrational (Raman) spectroscopies on several SiV-doped diamond nanoclusters.…”

Oxidation energies of shuttle molecules candidates in lithium‐ion batteries from double‐hybrid models

“…The main goal of this work is to analyze the efficiency of the recently developed functionals in the framework of double‐hybrid density functional theory (DH‐DFT), as the widely adopted models from the highest rung of DFT approximations, for predicting oxidation energies of organic compounds from different categories prone to be employed as shuttle molecules candidates. Although several works in the framework of DFT using conventional functionals, with emphasis on oxidation energies as well as other energetic and spectroscopic properties, have been carried out in recent years, it is necessary to evaluate the accuracy of the DH functionals for computational description of oxidation energies of shuttle molecules. In turn, this leads to unveiling the range of the accountability of modern DFT approximations and identifying improvement areas for design of novel DHs.…”

Theoretical Modeling of the Non-equilibrium Amorphous State in 1T-TaS2

“…Other methods deal with the polaron dynamics and include Ehrenfest dynamics [16,17], time-dependent density functional theory (TDDFT) [18], the multiconfiguration time-dependent Hartree method [19], its multilayer formulation [20] and the hierachical equations of motion [21,22]. TDDFT has been proven particularly successful in studying phenomena involved in polaron formation and dynamics, such as transient vibration energy redistribution and spectroscopy [23] and defects in nanomaterials [24,25].…”