Light Emitting Spin Active Electronic States in Ultra-Thin Mn Doped CdSe Layered Nanosheets (original) (raw)
Related papers
2018
Manganese doped cadmium sulfide diluted Magnetic Semiconductor nanoparticles (CdS:Mn) NPs have been prepared by wet chemical precipitation method at different Mn weight percentages (0, 2, 4, 6, 8, and 10%). Mercaptoethanol is the capping agent that used to form the nanostructure and prevent the aggregations of the particles. The structure properties of the obtained nanoparticles have been studied using xray diffraction pattern. Energy dispersive x-ray carried out to specify the chemical composition of the prepared nanoparticles. The optical properties have been determined by analysis of UV-vis and PL spectra. Vibrating sample magnetometer (VSM) technique used to identify the magnetic properties of the samples. The crystal size estimated from (XRD) of the prepared NPs was around ~ (4 7) nm with cubic zinc blende structure. EDX spectroscopy was used to confirm the incorporation of Mn at CdS lattice. The energy band gap of the nanoparticles has been estimated using UV-Vis spectroscopy....
Magneto-photoluminescence studies of Cd(Mn)Se/Zn(Mn)Se diluted magnetic nanostructures
Physica E: Low-dimensional Systems and Nanostructures, 2001
We report on cw and time-resolved photoluminescence (PL) studies of Cd(Mn)Se=Zn(Mn)Se diluted magnetic semiconductor nanostructures grown by molecular beam epitaxy. Excitonic PL intensity, decay time and Zeeman splitting have been studied systematically as a function of Cd(Mn)Se nominal thickness, Mn concentration and sample design. Wave function mapping has been performed, evidencing the formation of semi-magnetic quantum disk islands in the samples with thick enough Cd(Mn)Se insertions.
Iron substitution in CdSe nanoparticles: Magnetic and optical properties
Physical Review B, 2009
Chemically synthesized, thiol capped undoped, and Fe doped CdSe nanoparticles ͑NPs͒ have been investigated using a variety of physicochemical techniques. The electron spin resonance spectra exhibit two distinct signals at g ϳ 4 and g ϳ 2 characteristic of Fe 3+ ions occupying highly asymmetric and nearly symmetric lattice sites, respectively. The room temperature Mössbauer studies show a broad asymmetric doublet with isomer shift ϳ0.35 mm/ sec, quadrupole splitting ϳ0.76 mm/ sec characteristic of high spin ferric ions occupying the Cd 2+ sites with associated changes in local lattice environment. The room temperature photoluminescence spectra show transition from excited state Fe 3+ ͑ 4 T 1 , 4 T 2 , and 4 E͒ to the ground-state Fe 3+ ͑ 6 A 1 ͒ and also suggest that photoexcited electrons are preferentially transferred to iron ion induced trapping centers in CdSe nanoparticles. Room-temperature ferromagnetism is also observed in thiol capped Fe doped CdSe nanoparticles. Significant changes in saturation magnetization value with increasing iron concentration have been observed. The origin of room temperature ferromagnetism and significant change in M s value are discussed in terms of F-center exchange mechanism ͑bound magnetic polarons͒.
Inducing ferromagnetism in surface stabilised intrinsic CdSe nanoparticles by a simple process
Materials Science and Technology, 2020
In this letter, we report a simple process to derive in situ surface stabilised intrinsic CdSe nanoparticles (NPs) showing room temperature ferromagnetism (RTFM). The observed RTFM is primarily attributed to the lattice strain () in the NPs supported by an effective core (CdSe)-shell (surface layer) charge transfer mechanism. The synthesis method allows precise control over particle morphology and dispersity, and is highly convenient in tuning the magnetic properties for pertinent applications. Highlights • Magnetic CdSe nanoparticles were synthesized by a facile process. • In situ formed graphitic-carbon layer on the surface stabilises the nanoparticles. • The process permits precise control over particle morphology and dispersity. • The technique is also convenient in tuning the magnetic properties. • Monodispersed magnetic CdSe nanoparticles have potential applications in modern optoelectronics.
Physical Chemistry Chemical Physics, 2012
Cd 1Àx Mn x S nanoparticles (NPs) were successfully grown in a glass matrix and investigated by optical absorption (OA), magnetic circularly polarized photoluminescence (MCPL) measurements, and magnetic force microscopy (MFM). The room temperature OA spectra have revealed the formation of two groups of Cd 1Àx Mn x S NPs with different sizes: bulk-like nanocrystals (NCs) and quantum dots (QDs). The MCPL spectra were recorded at 2.0 K with several magnetic fields up to 15 T, allowing a detailed comparison between the degrees of circular polarization of the two groups of NPs. The different behaviours of magneto-optical properties of bulk-like NCs and QDs were explained by taking into account a considerable alteration of exchange interaction between the carrier spins and the substitutional doping magnetic ions incorporated into the NPs. As a main result, we have demonstrated that self-purification is the dominant mechanism that controls the doping in semiconductor QDs grown by the melting-nucleation synthesis approach due to the relatively high temperature that was used in thermal annealing of samples.
Chemistry of Materials, 2005
Arrays of highly ordered Cd 1-x Mn x S nanoparticles with x ranging from 0.01 to 0.2 and with lateral dimensions of 3, 6, and 9 nm were synthesized within mesoporous SiO 2 host structures of the MCM-41 and SBA-15 type. The hexagonal symmetry of these arrays (space group p6m) and the high degree of order were confirmed by X-ray diffraction and transmission electron microscope studies. Physisorption measurements show the progressive filling of the pores of the SiO 2 host structures, while photoluminescence excitation (PLE) and electron paramagnetic resonance (EPR) studies confirm the good crystalline quality of the incorporated Cd 1-x Mn x S guest species. The effects of the reduction of the lateral dimensions on the electronic properties of the diluted magnetic semiconductor were studied by PLE spectroscopy. Due to the quantum confinement of the excitons in the nanostructures an increase of the direct band gap with decreasing particle size as well as a stronger band gap bowing is observed. Analysis of the EPR line width and EPR intensity show that macroscopic magnetic properties such as the Curie-Weiss temperature are affected by the reduction of the lateral dimensions. The microscopic coupling between the Mn ions (e.g., the exchange constants J nn and J nnn ) is not altered to a first approximation.
Journal of Magnetism and Magnetic Materials, 2011
We have investigated the structural, electronic and magnetic properties of the diluted magnetic semiconductor (DMS) Cd1-xMnxTe (for x=0.75 and 1.0) in the zinc blende (B3) phase by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the frame work of spin-polarized density functional theory (SP-DFT). The electronic exchange-correlation energy is described by generalized gradient approximation (GGA). We have calculated the lattice parameters, bulk modulii and the first pressure derivatives of the bulk modulii, spin-polarized band structures, and total and local densities of states. We estimated the spin-exchange splitting energies Δx(d) and Δx(pd) produced by the Mn3d states, and we found that the effective potential for the minority spin is more attractive than that of the majority spin. We determine the s-d exchange constant N0α (conduction band) and p-d exchange constant N0β (valence band) and these somewhat agree with a typical magneto-optical experiment. The value of calculated magnetic moment per Mn impurity atom is found to be 4.08 μB for Cd0.25Mn0.75Te and 4.09 μB for Cd0.0Mn1.0Te. Moreover, we found that p-d hybridization reduces the local magnetic moment of Mn from its free space charge value of 5.0 μB and produces small local magnetic moments on the nonmagnetic Cd and Te sites.
2015
Copper doped CdS nanorods were synthesized using spin coating of gel. The gel was formed by new ultra sonicated sol gel route. Fine green and blue colored particles were appeared and filtered for characterization. The samples were analyzed by XRD, SEM, FTIR, Optical transmission and Photoluminescence studies. X ray diffractograms show single broad peak of (101) for undoped CdS. Intensity of this peak increases with increase in Copper doping concentration. Large numbers of islands were observed for undoped CdS. On increasing Cu doping these islands grow as more and more particles bind together and start to re assemble in ordered rodlike structures. Decrease in bandgap and increase in PL with increasing copper concentration make these structures suitable for tunable optoelectronic devices.
Nanocrystals of CdS/Mn2+ synthesized using sodium lauryl sulphate (SLS) surfactant and two ligands, i.e. butylenediamine (BD) and propylenediamine (PD), of differing lengths show a dominant presence of the hexagonal phase. The increasing [Mn2+] in the CdS/Mn2+ crystals from BD medium leads to a red shift in the band gap absorption with increasing intensity while the optical properties are reversed in CdS/PD crystals. Such changes can be explained by the switching of the randomly blinking nanocrystals into coherently emitting nanocrystals. The photoluminescence of CdS/Mn2+ materials with similarities and differences between SLS/BD and SLS/PD media exhibits two emissions: at 2.25 eV due to cadmium ion vacancies exhibiting Davydov-type splitting from neighbouring Cd2+–Cd2+ vacancies, and at 2.18 eV from manganese d–d emission. Thus, addition of Mn2+ leads to a decrease in the intensity of vacancy emission and increase in d–d emission due to occupation of cadmium vacant sites by manganese. Interestingly, SLS/PD medium creates more defects in CdS nanocrystals than SLS/BD medium. Note that the CdS/Mn2+ nanocrystals made from SLS/BD medium exhibit weak ferromagnetism in pre-annealed samples, becoming stronger after annealing, while the preannealed samples from SLS/PD origin have the simultaneous presence of both superparamagnetism and ferromagnetism, which turns to complete ferromagnetism on annealing. An attempt has also been made to compare the various properties of nanomaterials made as a function of two surfactants and three diamines of differing lengths. These nanoparticles are in the size range of 10 to 15 nm. A simple photo-resistance experiment on CdS and carbon nanoparticles-based heterostructure reveals its photosensitivity.
Structural, optical and magnetic properties of Mn 2+ doped ZnO-CdS composite nanopowder
Chemical precipitation method was used for the synthesis of Mn 2+ doped ZnO-CdS composite nanopow-der. The effect of Mn 2+ doping was investigated on their structural, optical and magnetic properties. XRD pattern reveals the hexagonal phase of ZnO as well as CdS and the average crystallite size is found to be 18 nm. The morphological studies show non-uniformly distributed spherical like structures with little agglomeration. Crystal field and interelectronic repulsion parameters are evaluated from optical absorption study. EPR spectrum exhibits a well resolved sextet at g = 1.9924. By correlating optical and EPR studies, Mn 2+ ions occupy octahedral sites in the host lattice which is also confirmed by PL analysis. From 1931 CIE chromaticity diagram, the prepared sample exhibits orange-red emission. IR spectrum confirms the existence of Zn-O and Cd-S vibrational modes. Room temperature ferromagnetism is observed in the prepared sample.