Blinking and single-photon emission can be tailored in CdSe/CdS core/shell colloidal dot-in-rods. By increasing the shell thickness it is possible to obtain almost non-blinking nanocrystals, while the shell length can be used to control single-photon emission probability.

Blinking effect and multi-excitonic emission can be independently addressed by tuning both core and shell dimension. By confocal techniques measurement, we show dot-in-rods as blinking-free sources of single photon on demand at room temperature.

We study the hole-spin relaxation in p-doped InAs quantum dots. Two relaxation mechanisms are evidenced, at low magnetic field ($0\ensuremath{\le}B\ensuremath{\le}2T$) and low temperature ($2\ensuremath{\le}T\ensuremath{\le}50K$), by using a pump-probe configuration and a recent experimental technique working in the frequency domain. At $T=2K$, the coupling to nuclear spins and the hole wave-function inhomogeneity fix the hole-spin relaxation rate value, ${\ensuremath{\Gamma}}_{1}^{h}\ensuremath{\approx}1\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}{\mathrm{s}}^{\ensuremath{-}1}$. It decreases with increasing magnetic field and reaches a plateau at 0.4 $\ensuremath{\mu}{\mathrm{s}}^{\ensuremath{-}1}$. At $T\ensuremath{\ge}7K$, two-phonon spin-orbit process dominates and leads to a quadratic temperature dependence of ${\ensuremath{\Gamma}}_{1}^{h}$, in good agreement with theory.

We study, at low temperature and zero magnetic field, the hole-spin dynamics in InAs/GaAs quantum dots. We measure the hole-spin relaxation time at a time scale longer than the dephasing time (about ten nanoseconds), imposed by the hole-nuclear hyperfine coupling. We use a pump-probe configuration and compare two experimental techniques based on differential absorption. The first one works in the time domain, and the second one is a new experimental method, the dark-bright time-scanning spectroscopy (DTS), working in the frequency domain. The measured hole-spin relaxation times, using these two techniques, are very similar, in the order of ${T}_{N}^{h}\ensuremath{\approx}$1 \ensuremath{\mu}s. It is mainly imposed by the inhomogeneous hole hyperfine coupling in the hole localization volume. The DTS technique allows us also to measure the hole-spin initialization time ${\ensuremath{\tau}}_{i}$. The hole spin is initialized by a periodic train of circularly polarized pulses at 76 MHz; we have observed that ${\ensuremath{\tau}}_{i}$ decreases as the power density increases, and we have measured a minimum value of ${\ensuremath{\tau}}_{i}\ensuremath{\approx}$100 ns in good agreement with a simple model [see B. Eble, P. Desfonds, F. Fras, F. Bernardot, C. Testelin, M. Chamarro, A. Miard, and A. Lema\^{\i}tre, Phys. Rev. B 81, 045322 (2010)].

We have performed pump-probe experiments in $p$-doped InAs/GaAs quantum dots leading to the all-optical initialization and readout of hole spins. In order to describe these experiments, we have modelized the interconnected dynamics of the photoelectron spin and the resident hole spin, triggered through the optical excitation by a train of short pulses. A complete description of this spin dynamics is obtained by including the hyperfine coupling as the common decoherence mechanism for the electron and hole spins. Periodic excitation conditions for arbitrary values of the pump power and the external magnetic field are also included in the model. In particular, a good agreement concerning the temporal behavior of the photoinduced circular dichroism is obtained for zero or low magnetic fields. When the applied magnetic field screens the hole-hyperfine interaction, we show that the agreement between the experimental and calculated time-dependent curves requires an additional relaxation mechanism for holes with a characteristic time in the microsecond range.

The spin dynamics of a resident carrier, hole or electron, in singly charged InAs/GaAs quantum dots has been measured by pump-probe experiments. The relative strength of the hole to the electron hyperfine couplings with nuclei is obtained by studying the magnetic-field dependence of the resident-carrier spin polarization. We find, in good agreement with recent theoretical studies, that the hole hyperfine coupling is ten times smaller than the electron one.

We model pump-probe experiments leading to the all-optical initialization of the hole spin of a p-doped InAs/GaAs quantum dots ensemble. We consider selection rules of mixed hole states and include periodic excitation conditions. Hyperfine interaction is taken into account as the common decoherence mechanism for the spins of electrons and holes. We show that the degree of hole spin polarization can be maximized by quenching the action of the hole hyperfine interaction with a small applied magnetic field. However additional hole spin relaxation mechanisms, in the microsecond time range, determine the absolute value of this maximum.

We have measured the carrier spin dynamics in p-doped InAs/GaAs quantum dots by pump-probe and time-resolved photoluminescence experiments. We obtained experimental evidence of the hyperfine interaction between hole and nuclear spins. In the absence of an external magnetic field, our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei lead to a hole-spin dephasing time for an ensemble of dots of 14 ns, in close agreement with experiments.

Fe 1.5 Ti 0.5 O 3 ± δ epitaxial thin films have been grown on α-Al2O3 (0001) substrates by pulsed laser deposition technique. The samples are both ferrimagnetic and semiconducting beyond room temperature. Oxygen pressure (PO2) during the deposition appears to be a critical parameter in promoting high temperature long range magnetic order and semiconducting properties. For all oxygen pressures, Fe1.5Ti0.5O3±δ thin films are single phase with twin epitaxy. High dc conductivity and low magnetization are obtained at low PO2, whereas high saturation magnetization and low conductivity stand for high PO2. Oxygen vacancies and∕or change of iron valence state are pointed out to be responsible of these properties. Superexchange mechanism via oxygen bonds seems rather to dominate the magnetic properties especially for high PO2, whereas for low PO2 a double exchange mechanism might occur. Fe1.5Ti0.5O3±δ appears thus to be an interesting material for high temperature spintronics applications.

In n-type diamond doped with phosphorus, exciton properties have been investigated by cathodoluminescence as a function of the phosphorus concentration and the temperature. The homoepitaxial diamond layers were grown by microwave plasma-assisted chemical vapor deposition and doped using a liquid organic precursor of phosphorus (tertiarybutylphosphine). The phosphorus concentration ranges from 5.2×1016 to 3.3×1018 cm−3 as measured by secondary ion mass spectrometry. It is shown that the ratio between the luminescence intensities of the neutral phosphorus-bound exciton and the free exciton follows the dopant concentration. Calibration graphs are presented to determine the phosphorus contents in diamond using cathodoluminescence spectroscopy.