Bright room temperature single photon source at telecom range in cubic silicon carbide

Single photon emitters (SPEs) play an important role in a number of quantum information tasks such as quantum key distributions. In these protocols, telecom wavelength photons are desired due to their low transmission loss in optical fibers. In this paper, we present a study of bright single-photon emitters in cubic silicon carbide (3C-SiC) emitting in the telecom range. We find that these emitters are photostable and bright at room temperature with a count rate of ~ MHz. Together with the fact that SiC is a growth and fabrication-friendly material, our result may pave the way for its future application in quantum communication technology applications.Comment: Accepted by Nature Communication

Surface acoustic wave driven ferromagnetic resonance in (Ga,Mn)(As,P) epilayers

Interdigitated transducers were used to generate and detect surface acoustic waves on a thin layer of (Ga,Mn)(As,P). The out-of-plane uniaxial magnetic anisotropy of this dilute magnetic semiconductor is very sensitive to the strain of the layer, making it an ideal test material for the dynamic control of magnetization via magneto-striction. The time-domain measurement of the amplitude and phase of the transmitted SAW during magnetic field sweeps indicated a clear resonant behavior at a field close to the one calculated to give a precession frequency equal to the SAW frequency. A resonance was observed from 5K to 85K, just below the Curie temperature of the layer. A full analytical treatment of the coupled magnetization/acoustic dynamics showed that the magneto-strictive coupling modifies the elastic constants of the material and accordingly the wave-vector solution to the elastic wave equation. The shape and position of the resonance were well reproduced by the calculations, in particular the fact that velocity (phase) variations resonated at lower fields than the acoustic attenuation variations

Irreversible magnetization switching using surface acoustic waves

An analytical and numerical approach is developped to pinpoint the optimal experimental conditions to irreversibly switch magnetization using surface acoustic waves (SAWs). The layers are magnetized perpendicular to the plane and two switching mechanisms are considered. In precessional switching, a small in-plane field initially tilts the magnetization and the passage of the SAW modifies the magnetic anisotropy parameters through inverse magneto-striction, which triggers precession, and eventually reversal. Using the micromagnetic parameters of a fully characterized layer of the magnetic semiconductor (Ga,Mn)(As,P), we then show that there is a large window of accessible experimental conditions (SAW amplitude/wave-vector, field amplitude/orientation) allowing irreversible switching. As this is a resonant process, the influence of the detuning of the SAW frequency to the magnetic system's eigenfrequency is also explored. Finally, another - non-resonant - switching mechanism is briefly contemplated, and found to be applicable to (Ga,Mn)(As,P): SAW-assisted domain nucleation. In this case, a small perpendicular field is applied opposite the initial magnetization and the passage of the SAW lowers the domain nucleation barrier.Comment: 11 pages, 4 figure

Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [001] to in-plane [100] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam

Structural, EPR and optical properties of Zn

ZnO nanopowders with different 3d transition metal (TM) doping (TM = Mn, Fe, Co, Ni) were synthesized by a new protocol based on slow hydrolyse of zinc acetate dissolved in methanol and supercritical drying in ethyl alcohol. The prepared Zn1−xTMxO (x = 0.25) nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical absorption and electron paramagnetic resonance spectroscopy (EPR). The results demonstrated that the TM dopant significantly affects the structural and magnetic properties of the samples. From the XRD spectra, the lattice parameters, average crystallite size and microstrain values were obtained. All ZnTMO nanoparticles show an expansion of the lattice parameters compared those of the bulk samples. Unit cell volume was minimized with Fe doping and increased as the atomic number of the dopant moved away from Fe. The XRD pattern indicates the formation of hexagonal wurtzite phase of ZnO for all the TM dopants. Electron microscopy characterization showed that the size of the Zn1−xTMxO particles is about 25 nm did not change significantly for the different dopants. Optical absorption measurements show that band gap energies of the TM-doped ZnO nanoparticles are around 3.2 eV. The Urbach energy of the ZnTMO nanopowders varies with the TM dopant. From magnetic measurements we observed the presence of room temperature ferromagnetic order in our TM-doped ZnO samples. EPR spectra confirm that TM ions were mainly incorporated as TM2+, occupying the Zn2+ sites in the wurtzite structure of ZnO. Room temperature ferromagnetic order was observed only in Ni- and Co-doped ZnO samples, whereas Mn- and Fe-doped powders showed only antiferromagnetic and paramagnetic interactions, respectively. The correlation between the structural and magnetic properties as a function of the TM dopant is discussed

Magnetic resonance of semiconductors and their nanostructures: basic and advanced applications

This book explains different magnetic resonance (MR) techniques and uses different combinations of these techniques to analyze defects in semiconductors and nanostructures. It also introduces novelties such as single defects MR and electron-paramagnetic-resonance-based methods: electron spin echo, electrically detected magnetic resonance, optically detected magnetic resonance and electron-nuclear double resonance – the designated tools for investigating the structural and spin properties of condensed systems, living matter, nanostructures and nanobiotechnology objects. Further, the authors address problems existing in semiconductor and nanotechnology sciences that can be resolved using MR, and discuss past, current and future applications of MR, with a focus on advances in MR methods. The book is intended for researchers in MR studies of semiconductors and nanostructures wanting a comprehensive review of what has been done in their own and related fields of study, as well as future perspectives

Systematic study of the spin stiffness dependence on Phosphorus alloying in (Ga,Mn)As ferromagnetic semiconductor

We study the dependence of the spin stiffness constant on the phosphorus concentration in the ferromagnetic semiconductor (Ga,Mn)(As,P) with the aim of determining whether alloying with phosphorus is detrimental, neutral or advantageous to increase the spin stiffness. Time resolved magneto-optical experiments are carried out in thin epilayers. Laser pulses excite two perpendicular standing spin wave modes which are exchange related. We show that the first mode is spatially uniform across the layer corresponding to a $k\approx$0 wavevector. From the two frequencies and k-vector spacings we obtain the spin stiffness constant for different phosphorus concentrations using weak surface pinning conditions. The mode assessment is checked by comparison with the spin stiffness obtained from domain pattern analysis for samples with out-of-plane magnetization and with ferromagnetic resonance experiments when more than one spin wave mode is observed. The spin stiffness is found to exhibit little variation with phosphorus concentration in contradiction with ab-initio predictions

High domain wall velocities in in-plane magnetized (Ga,Mn)(As,P) layers

International audienceField-induced domain wall (DW) propagation was evidenced in unpatterned layers of in-plane magnetized Ga1−xMnxAs1−yPy using Kerr microscopy. Both stationary and precessional regimes were observed, and domain wall velocities of up to 500 m s −1 were measured, of the order of magnitude of those observed on in-plane magnetized metals. Taking advantage of the strain-dependent magneto-crystalline anisotropy in this dilute magnetic semiconductor, both out-of-plane and in-plane anisotropies were adjusted by varying the manganese and phosphorus concentrations. We demonstrate that these anisotropies are a critical parameter to obtain large velocities. These results are interpreted in the framework of the one-dimensional model for domain wall propagation