53 research outputs found
Photophysics of single nitrogen-vacancy centers in diamond nanocrystals
A study of the photophysical properties of nitrogen-vacancy (NV) color
centers in diamond nanocrystals of size of 50~nm or below is carried out by
means of second-order time-intensity photon correlation and cross-correlation
measurements as a function of the excitation power for both pure charge states,
neutral and negatively charged, as well as for the photochromic state, where
the center switches between both states at any power. A dedicated three-level
model implying a shelving level is developed to extract the relevant
photophysical parameters coupling all three levels. Our analysis confirms the
very existence of the shelving level for the neutral NV center. It is found
that it plays a negligible role on the photophysics of this center, whereas it
is responsible for an increasing photon bunching behavior of the negative NV
center with increasing power. From the photophysical parameters, we infer a
quantum efficiency for both centers, showing that it remains close to unity for
the neutral center over the entire power range, whereas it drops with
increasing power from near unity to approximately 0.5 for the negative center.
The photophysics of the photochromic center reveals a rich phenomenology that
is to a large extent dominated by that of the negative state, in agreement with
the excess charge release of the negative center being much slower than the
photon emission process
Switchable ErSc2N rotor within a C80 fullerene cage: An EPR and photoluminescence excitation study
Systems exhibiting both spin and orbital degrees of freedom, of which Er3+ is
one, can offer mechanisms for manipulating and measuring spin states via
optical excitations. Motivated by the possibility of observing
photoluminescence and electron paramagnetic resonance from the same species
located within a fullerene molecule, we initiated an EPR study of Er3+ in
ErSc2N@C80. Two orientations of the ErSc2N rotor within the C80 fullerene are
observed in EPR, consistent with earlier studies using photoluminescence
excitation (PLE) spectroscopy. For some crystal field orientations, electron
spin relaxation is driven by an Orbach process via the first excited electronic
state of the 4I_15/2 multiplet. We observe a change in the relative populations
of the two ErSc2N configurations upon the application of 532 nm illuminations,
and are thus able to switch the majority cage symmetry. This
photoisomerisation, observable by both EPR and PLE, is metastable, lasting many
hours at 20 K.Comment: 4 pages, 4 figure
Spin relaxometry of single nitrogen-vacancy defects in diamond nanocrystals for magnetic noise sensing
We report an experimental study of the longitudinal relaxation time ()
of the electron spin associated with single nitrogen-vacancy (NV) defects
hosted in nanodiamonds (ND). We first show that decreases over three
orders of magnitude when the ND size is reduced from 100 to 10 nm owing to the
interaction of the NV electron spin with a bath of paramagnetic centers lying
on the ND surface. We next tune the magnetic environment by decorating the ND
surface with Gd ions and observe an efficient -quenching, which
demonstrates magnetic noise sensing with a single electron spin. We estimate a
sensitivity down to electron spins detected within 10 s, using a
single NV defect hosted in a 10-nm-size ND. These results pave the way towards
-based nanoscale imaging of the spin density in biological samples.Comment: Main text with 4 figures together with supplemental informatio
Nanoscale magnetic field mapping with a single spin scanning probe magnetometer
We demonstrate quantitative magnetic field mapping with nanoscale resolution,
by applying a lock-in technique on the electron spin resonance frequency of a
single nitrogen-vacancy defect placed at the apex of an atomic force microscope
tip. In addition, we report an all-optical magnetic imaging technique which is
sensitive to large off-axis magnetic fields, thus extending the operation range
of diamond-based magnetometry. Both techniques are illustrated by using a
magnetic hard disk as a test sample. Owing to the non-perturbing and
quantitative nature of the magnetic probe, this work should open up numerous
perspectives in nanomagnetism and spintronics
Surface-induced charge state conversion of nitrogen-vacancy defects in nanodiamonds
We present a study of the charge state conversion of single nitrogen-vacancy
(NV) defects hosted in nanodiamonds (NDs). We first show that the proportion of
negatively-charged NV defects, with respect to its neutral counterpart
NV, decreases with the size of the ND. We then propose a simple model
based on a layer of electron traps located at the ND surface which is in good
agreement with the recorded statistics. By using thermal oxidation to remove
the shell of amorphous carbon around the NDs, we demonstrate a significant
increase of the proportion of NV defects in 10-nm NDs. These results are
invaluable for further understanding, control and use of the unique properties
of negatively-charged NV defects in diamondComment: 6 pages, 4 figure
Luminescence of a titanate compound under europium ion implantation
The ability to incorporate europium ions in a near-surface layer of a nonlinear optical material KTiOPO4 by ion implantation is reported here. Europium diffusion as well as surface modification were characterized after annealing using RBS. The photoluminescence of the as-implanted samples indicates that the creation of defects gives rise to green visible emission centered about 550 nm. Annealing up to 1000 °C does not allow the oxidation to the 3+ valence state of the europium ion. However it is shown that annealing up to such high temperature gives rise to an intense near infra-red photoluminescence in the range 800-1100 nm in implanted samples at an optimal fluence of 2 × 1013 europium ions/cm2
Switchable ErSc2N rotor within a C80 fullerene cage: An electron paramagnetic resonance and photoluminescence excitation study
Motivated by the possibility of observing photoluminescence and electron paramagnetic resonance from the same species located within a fullerene molecule, we initiated an EPR study of Er3+ in ErSc2N@C80. Two orientations of the ErSc2N rotor within the C80 fullerene are observed in EPR, consistent with earlier studies using photoluminescence excitation (PLE) spectroscopy. For some crystal field orientations, electron spin relaxation is driven by an Orbach process via the first excited electronic state of the 4I15/2 multiplet. We observe a change in the relative populations of the two ErSc2N configurations upon the application of 532 nm illumination, and are thus able to switch the majority cage symmetry. This photoisomerization, observable by both EPR and PLE, is metastable, lasting many hours at 20 K. © 2008 The American Physical Society
Temperature-dependent photoluminescence study of ErSC2N@C-80 and Er2ScN@C-80 fullerenes
The photoluminescence study of the Er3+ ion in ErSc 2N@C80 and Er2ScN@C80 fullerenes in the temperature range of 5 K to 80 K is presented. New emission peaks are observed for both fullerenes above 20 K. These peaks arise from thermally populated crystal-field levels of the excited state. An anomalous behaviour of the PL peak area is observed with an increasing temperature which reveals an internal rearrangement of the cluster ErSc2N in ErSc 2N@C80. © 2008 Wiley-VCH Verlag GmbH and Co. KGaA
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