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61.
Temperatures of 1000 °C and higher are a significant problem for the incorporation of erbium-doped silicon nanocrystal devices into standard silicon technology, and make the fabrication of contacts and reflectors in light emitting devices difficult. In the present work, we use energy-filtered TEM imaging techniques to show the formation of size-controlled amorphous silicon nanoclusters in SiO films annealed between 400 and 500 °C. The PL properties of such films are characteristic of amorphous silicon, and the spectrum can be controlled via a statistical size effect—as opposed to quantum confinement—that has previously been proposed for porous amorphous silicon. Finally, we show that amorphous nanoclusters sensitize the luminescence from the rare-earth ions Er, Nd, Yb, and Tm with excitation cross-sections similar in magnitude to erbium-doped silicon nanocrystal composites, and with a similar nonresonant energy transfer mechanism. 相似文献
62.
掺杂Mn2+的浓度对CdS纳米颗粒光致发光的影响 总被引:2,自引:2,他引:0
赵普琴 《原子与分子物理学报》2006,23(6):1117-1122
采用反胶束法,合成了硅土包裹的掺有不同浓度的Mn2 的CdS纳米颗粒.高分辨电镜表明这些颗粒的直径小于5 nm.仅仅改变Mn2 的掺杂浓度,研究了这些颗粒的光致发光谱和光致发光激发谱,结果表明:Mn2 浓度的大小对掺杂CdS纳米颗粒的发光产生了重要的影响.通过电子顺磁共振谱的测量和分析揭露了Mn2 浓度影响这些掺杂颗粒发光效率的原因. 相似文献
63.
The optical and structural properties of mixed ZnO/MgO particles prepared by solution techniques are investigated by the cathodoluminescence and electron microscopy techniques. The samples annealed at 400–1000 °C show well crystalline wurtzite structure of the ZnO (MgZnO) particles with the size in range of 10–100 nm. Annealing at high temperatures (>700 °C) leads to Mg diffusion in ZnO and MgxZn1−xO alloy formation. The blue shifts of the near-band-edge emission as a result of the alloy band gap widening and quantum confinement effect for the small size particles are demonstrated. 相似文献
64.
CdS nanocrystals with a beltlike morphology were prepared via a low-temperature solvothermal route in ethylenediamine. The obtained nanocrystals were characterized by X-ray powder diffraction, transmission electron microscopic, ultraviolet-visible and fluorescence spectroscopy. In the mixed solvents of ethylenediamine and distilled water, CdS nanocrystals with various morphologies were obtained with the change of the volume ratio of the two constituents. 相似文献
65.
M. Galceran M. C. Pujol M. Aguiló F. Díaz 《Journal of Sol-Gel Science and Technology》2007,42(1):79-88
KRE(WO4)2 (RE = Gd and Yb) nanocrystalline powder was obtained by the modified sol-gel Pechini method. The precursor powder was calcined
between 923 and 1023 K for a maximum of 6 h at air atmosphere. DTA-TG of the precursor powder shows that the temperature for
total calcination is around 800–850 K. Molar ratio between the complexing agent and the metal ions in the first step of the
method and molar ratio between the complexing agent and the ethylene glycol in the second step of the method were studied
to optimize the preparation process. X-ray diffraction and IR spectroscopy were used to study the transformation from precursor
powder into a crystalline monoclinic phase. Raman spectroscopy was used to study the vibrational structure of the nanoparticles.
The Scherrer formula was used to confirm the grain sizes visualized by SEM and TEM techniques. Small nanoparticles in the
range of 20–50 nm of monoclinic KREW have been successfully obtained by this methodology. 相似文献
66.
This review points out that (magneto-)optical measurements may help to shine light on the recombination processes taking place
in semiconductor nanocrystals. The surface capping with thiols creates a CdS shell around CdTe cores and forms a Cd site that
is not fourfold-coordinated at the surface. It is pointed out how specific cappings such as thio-amines and thio-acids assist
in coupling NCs and how we may distinguish between NC–NC interactions via electrostatic and covalent linking with the aid
of the optical measurements. Furthermore, with static and time-resolved ODMR studies on IR-active core-shell HgTe/Hg
x
Cd1−x
Te(S) particles it is demonstrated how the nature of the recombination emission being associated with a Cd–Hg mixed site is
elucidated and by this yielding structural information on the NC core-shell interface. With these examples we show that and
how nanomaterials of probable technological interest are studied beneficially with advanced spectroscopic techniques. 相似文献
67.
A facile CTAB-assisted sol-gel route has been successfully established to synthesize Y2Sn2O7 nanocrystals with pyrochlore structure. The route involves first the formation of CTAB-inorganics mesostructures as precursors and then their thermal decomposition to yield the final product. Well-crystallized and phase-pure Y2Sn2O7 particles of ∼40 nm in size can be readily obtained at 600°C, a temperature much lower than that of the conventional solid-state method. Furthermore, photoluminescence characterization of the Y2Sn2O7 nanocrystals doped with 5 mol% Eu3+ was carried out and the results show that the as-synthesized material display intense and prevailing emission at 589 nm belonging to the magnetic dipole transition. 相似文献
68.
We succeeded in fabricating nanoscale arrays of polymers based on hydroxylated poly(butyl methacrylate-b-glycidyl methacrylate) which was prepared via a novel atom-transfer radical polymerization technique. Nanosized latex particles of the copolymer were obtained in the tetrahydrofuran/toluene solvent system. By evaporation of the latex solution on a substrate, the ordered self-organization monolayer was formed. Rather regular, two-dimensional arrays of nanopaticles with diameters down to approximately 12 nm were observed by means of transmission electron microscopy. The regular nature of the arrays can be controlled well by depositing the monolayer at a lower temperature. 相似文献
69.
Changlong Jiang Liyang Wang Kunihito Kuwabara 《Journal of solid state chemistry》2007,180(11):3146-3151
Cobalt nanocrystals were prepared by controlled chemical route at mild condition through selective-precursor reducing synthesis. Nanorod bundles and three-dimensional (3D) dendritic nanocrystal networks of Co were prepared by selecting different precursors. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) technologies. Field-emission scanning electron microscopy (FE-SEM), SEM, and TEM images indicate the nanorod bundles mainly consist of nanorods with the diameter of 70 nm. In 3D dendritic nanocrystal networks there are numerous secondary and sub-secondary branches were grown at right angles on each main stem. Room temperature magnetic measure of the Co samples demonstrates much enhanced ferromagnetic property, which might be attributed to their organization of specific shape. The possible formation mechanism of the cobalt nanocrystals with different morphologies was also discussed. 相似文献
70.
Olivia Pulci Elena Degoli Federico Iori Margherita Marsili Maurizia Palummo Rodolfo Del Sole Stefano Ossicini 《Superlattices and Microstructures》2010
First-principles calculations within density functional theory and many-body perturbation theory have been carried out in order to investigate the structural, electronic and optical properties of undoped and doped silicon nanostructures. We consider Si nanoclusters co-doped with B and P. We find that the electronic band gap is reduced with respect to that of the undoped crystals, suggesting the possibility of impurity based engineering of electronic and optical properties of Si nanocrystals. Finally, motivated by recent suggestions concerning the chance of exploiting Ge dots for photovoltaic nanodevices, we present calculations of the electronic and optical properties of a Ge35H36 nanocrystal, and compare the results with those for the corresponding Si35H36 nanocrystals and the co-doped Si33BPH36. 相似文献