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1.
Si/SiO2 Fabry–Pérot microcavities with a silicon nanocrystal (Si-nc) active spacer have been realized using a novel process based
on a reactive magnetron sputtering of a pure silica target. Spectral, spatial and temporal behaviours of the quantum dots
confined inside the resonator are detailed. Compared with a reference sample, the spectral and spatial emission distributions
are significantly narrowed and the forward emission intensity is enhanced. Time resolved photoluminescence measurements also
revealed an increase of the spontaneous emission rate.
PACS 42.70.Qs; 78.55.-m; 78.66.-w 相似文献
2.
I. R. Shein R. Wilks A. Moewes E. Z. Kurmaev D. A. Zatsepin A. I. Kukharenko S. O. Cholakh 《Physics of the Solid State》2008,50(4):615-620
The electronic structure of crystalline phenakite Be2SiO4 is investigated using x-ray emission spectroscopy (XES) (Be K α XES, Si L 2, 3 XES, O K α XES) and x-ray absorption spectroscopy (XAS) (Be 1s XAS, Si 2p XAS, O 1s XAS). The energy band structure is calculated by the ab initio full-potential linearized augmented-plane-wave (FLAPW) method. The total and partial densities of states and the dispersion curves for the Be2SiO4 compound are presented. It is shown that the top of the valence band and the bottom of the conduction band of the Be2SiO4 compound are predominantly formed by the oxygen 2p states. According to the results obtained, the electron transition with the lowest energy supposedly can occur at the center of the Brillouin zone. The effective masses of electrons (0.5m e ) and holes (3.0m e ) for the Be2SiO4) compound are estimated. 相似文献
3.
A. Akbari Tochaei H. Arabshahi M. R. Benam A. Vatan-Khahan M. Abedininia 《Journal of Experimental and Theoretical Physics》2016,122(5):869-873
The discrete breathers in graphane in thermodynamic equilibrium in the temperature range 50–600 K are studied by molecular dynamics simulation. A discrete breather is a hydrogen atom vibrating along the normal to a sheet of graphane at a high amplitude. As was found earlier, the lifetime of a discrete breather at zero temperature corresponds to several tens of thousands of vibrations. The effect of temperature on the decay time of discrete breathers and the probability of their detachment from a sheet of graphane are studied in this work. It is shown that closely spaced breathers can exchange energy with each other at zero temperature. The data obtained suggest that thermally activated discrete breathers can be involved in the dehydrogenation of graphane, which is important for hydrogen energetics. 相似文献
4.
The thermal effects produced by continuous-wave laser radiation on free-standing Si/SiO2 superlattices are studied. We compare two samples with different SiO2 layer thicknesses (2 and 6 nm) and the same Si layer thickness (2 nm). The as-prepared free-standing superlattices contain
some amount of Si nanocrystals (Si-nc). Intense laser irradiation at 488 nm of the as-prepared samples enhances the Raman
scattering of Si-nc by two orders of magnitude. This laser-induced crystallization originates from melting of Si nanostructures
in silica, which makes Si-nc better ordered and better isolated from the oxide surrounding. Continuous-wave laser control
of Si-nc stress was achieved in these samples. In the proposed model, intense laser radiation melts Si-nc, and Si crystallization
upon cooling down from the liquid phase in a silica matrix leads to compressive stress. The Si-nc stress can be tuned in the
∼3 GPa range using laser annealing below the Si melting temperature. The high laser-induced temperatures were verified with
Raman spectroscopy. The laser-induced heat leads to a strongly nonlinear rise of light emission. The light emission is also
observed in the anti-Stokes region, and its temperature dependence is practically the same for the two studied samples. The
laser-induced temperature is essentially controlled by the absorbed laser power.
PACS 78.55.-m; 78.20.-e; 68.55.-a; 78.30.-j 相似文献
5.
Using a pulsed microplasma source, clusters were produced through the ablation
of a Si cathode and successive supersonic expansion.
The Si cluster beam was deposited onto different substrates and the partial oxidation of the cluster
surface avoided the growth of large agglomerates, preserving their nanocrystalline morphology.
Micro-Raman spectroscopy was used for an accurate size diagnosis of the deposited nanoparticles. The size of the Si dots ranges between 2 and about 15 nm. The Si dots appear to have a Si oxide shell, as confirmed also by structural and compositional analysis through transmission electron microscopy and atomic force microscopy. Double Raman peaks were attributed to small Si agglomerates having a thin substoichiometric Si-O interface. 相似文献
6.
7.
I. Yu. Martynyuk-Lototska O. G. Mys S. V. Akimov O. M. Krupych R. O. Vlokh 《Opto-Electronics Review》2010,18(2):137-149
Interaction of acoustic and light waves with accounting for elastooptic and elastogyration effects is theoretically described.
Collinear acoustogyration diffraction in quartz and paratellurite crystals is experimentally investigated and thoroughly analyzed.
Piezogyration effect is experimentally studied for TeO2 crystals. The acoustogyration efficiency and the acoustogyration figure of merit calculated for a number of crystals (GaAs,
TeO2 and SiO2) are shown to be too small for experimental detection. On the other hand, we demonstrate that the light diffraction at periodical
distribution of the imaginary part of dielectric permittivity related to the piezogyration effect should, in principle, be
observed for the case of interaction of optical waves with enantiomorphous ferroelastic domain structure and in cholesteric
liquid crystals. 相似文献
8.
S. H. Park D. Ahn 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):29
Using the coupled cluster method we investigatespin-s
J
1-J′
2 Heisenberg antiferromagnets (HAFs) on an infinite, anisotropic, two-dimensional triangular lattice for the two cases where
the spin quantum number s = 1 and s = $\frac{3}
{2}$\frac{3}
{2}. With respect to an underlying square-lattice geometry the model has antiferromagnetic (J
1 > 0) bonds between nearest neighbours and competing (J′
2 > 0) bonds between next-nearest neighbours across only one of the diagonals of each square plaquette, the same diagonal in
each square. In a topologically equivalent triangular-lattice geometry, the model has two types of nearest-neighbour bonds:
namely the J′
2 ≡ κJ
1 bonds along parallel chains and the J
1 bonds producing an interchain coupling. The model thus interpolates between an isotropic HAF on the square lattice at one
limit (κ = 0) and a set of decoupled chains at the other limit (κ → ∞), with the isotropic HAF on the triangular lattice in between at κ = 1. For both the spin-1 model and the spin-$\frac{3}
{2}$\frac{3}
{2} model we find a second-order type of quantum phase transition at κ
c
= 0.615 ± 0.010 and κ
c
= 0.575 ± 0.005 respectively, between a Néel antiferromagnetic state and a helically ordered state. In both cases the ground-state
energy E and its first derivative dE/dκ are continuous at κ = κ
c
, while the order parameter for the transition (viz., the average ground-state on-site magnetization) does not go to zero
there on either side of the transition. The phase transition at κ = κ
c
between the Néel antiferromagnetic phase and the helical phase for both the s = 1 and s = $\frac{3}
{2}$\frac{3}
{2} cases is analogous to that also observed in our previous work for the s = $\frac{1}
{2}$\frac{1}
{2} case at a value κ
c
= 0.80 ± 0.01. However, for the higher spin values the transition appears to be of continuous (second-order) type, exactly
as in the classical case, whereas for the s = $\frac{1}
{2}$\frac{1}
{2} case it appears to be weakly first-order in nature (although a second-order transition could not
be ruled out entirely). 相似文献
9.
Influence of the Si/SiO<Subscript>2</Subscript> interface on the charge carrier density of Si nanowires 总被引:1,自引:0,他引:1
The electrical properties of Si nanowires covered by a SiO2 shell are influenced by the properties of the Si/SiO2 interface. This interface can be characterized by the fixed oxide charge density Qf and the interface trap level density Dit. We derive expressions for the effective charge carrier density in silicon nanowires as a function of Qf, Dit, the nanowire radius, and the dopant density. It is found that a nanowire is fully depleted when its radius is smaller than a critical radius acrit. An analytic expression for acrit is derived. PACS 68.65.-k; 61.46.+w; 81.10.Bk 相似文献
10.
V. V. Balashev V. V. Korobtsov T. A. Pisarenko L. A. Chebotkevich 《Technical Physics》2011,56(10):1501-1507
Magnetite polycrystalline films are grown by variously oxidizing a Fe film on the Si(111) surface covered by a thin (1.5 nm)
SiO2 layer. It is found that defects in the SiO2 layer influence silicidation under heating of the Fe film. The high-temperature oxidation of the Fe film results in the formation
of both Fe3O4 and iron monosilicide. However, the high-temperature deposition of Fe in an oxygen atmosphere leads to the growth of a compositionally
uniform Fe3O4 film on the SiO2 surface. It is found that such a synthesis method causes [311] texture to arise in the magnetite film, with the texture axis
normal to the surface. The influence of the synthesis method on the magnetic properties of grown Fe3O4 films is studied. A high coercive force of Fe3O3 films grown by Fe film oxidation is related to their specific morphology and compositional nonuniformity. 相似文献
11.
A. S. Shulakov A. P. Braiko S. V. Bukin V. E. Drozd 《Physics of the Solid State》2004,46(10):1935-1939
The phase chemical composition of an Al2O3/Si interface formed upon molecular deposition of a 100-nm-thick Al2O3 layer on the Si(100) (c-Si) surface is investigated by depth-resolved ultrasoft x-ray emission spectroscopy. Analysis is performed using Al and Si L2, 3 emission bands. It is found that the thickness of the interface separating the c-Si substrate and the Al2O3 layer is approximately equal to 60 nm and the interface has a complex structure. The upper layer of the interface contains Al2O3 molecules and Al atoms, whose coordination is characteristic of metallic aluminum (most likely, these atoms form sufficiently large-sized Al clusters). The shape of the Si bands indicates that the interface layer (no more than 10-nm thick) adjacent to the substrate involves Si atoms in an unusual chemical state. This state is not typical of amorphous Si, c-Si, SiO2, or SiOx (it is assumed that these Si atoms form small-sized Si clusters). It is revealed that SiO2 is contained in the vicinity of the substrate. The properties of thicker coatings are similar to those of the 100-nm-thick Al2O3 layer and differ significantly from the properties of the interfaces of Al2O3 thin layers. 相似文献
12.
The Si/SiO2 composites, in which the concentration of the conducting silicon phase is close to the percolation threshold, have been prepared
using the ceramic technology and studied at an alternating current. It has been found that an increase in the potential difference
in a direct-current electric field leads to a decrease in the dispersion of time constants of dielectric spacers in the “Si
grain-SiO2 spacer-Si grain” structures forming a conducting cluster in the composite. 相似文献
13.
S. E. Demyanov E. Yu. Kaniukov A. V. Petrov E. K. Belonogov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(9):1193-1195
Structures based on the SiO2/n-Si and SiO2/p-Si systems, with nanopores in silicon dioxide layers filled with Cu and Ni nanoparticles, have been prepared and investigated using the fast heavy ion technology, which includes irradiation with 197Au26+ ions, chemical etching of ion tracks, and subpotential electrochemical deposition. The selectivity of filling nanopores with metals and cluster character of their formation in tracks is shown. 相似文献
14.
T. N. Danilenko M. M. Tatevosyan V. G. Vlasenko 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(6):738-741
The electronic structure of SiO2 is investigated by means of valence to core X-ray emission spectroscopy and quantum-mechanical calculations in the density functional theory approximation. Analysis of a complete set of SiKα1, SiL2, 3, and OKα X-ray emission and XPS spectra along with the calculated data provides comprehensive information on chemical interactions that occur in SiO2. 相似文献
15.
V. S. Kovivchak R. B. Burlakov N. A. Davletkil’deev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(2):245-247
Nanoporous Si and SiO2 melting observed under high-power ion beam irradiation of nanosecond duration was investigated. The sizes of ellipsoidal
particles formed in Si and those of holes formed in SiO2 under irradiation were determined. The possible origin of these morphology features was discussed. 相似文献
16.
The structure of polycrystalline Fe films grown on an oxidized Si(001) surface at room temperature has been studied by the technique of high-energy electron diffraction. It has been found that the grain orientation in the films depends of the amount of deposited iron. In Fe films less than 5 nm thick, grains have been found to be randomly oriented. Fe films more than 5 nm in thickness exhibit the (111) texture with an axis coinciding with the surface normal. The angular dispersion of the [111] direction in the Fe lattice from the surface normal is ±25°. It has been found that as the Fe films become thicker, the (111) texture changes to the (110) texture. 相似文献
17.
G. Schrems M.P. Delamare N. Arnold P. Leiderer D. Bäuerle 《Applied Physics A: Materials Science & Processing》2003,76(5):847-849
The influence of the ‘storage time’ τs on the threshold fluence φcl and the efficiency in dry laser cleaning is investigated. τs denotes the time between the deposition of particles and the cleaning. As a model system we employed silica spheres with
diameters of 500 nm and 1500 nm on commercial silicon wafers and single-pulse KrF excimer laser radiation (τFWHM=28 ns). For the 1500-nm silica spheres, φcl was found to increase from about 65 mJ/cm2 to 125 mJ/cm2 for storage times of 4 h and 362 h, respectively. For 500-nm silica spheres the increase in the threshold fluence was less
than 20% for storage times up to 386 h.
Received: 12 July 2002 / Accepted: 12 July 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. E-mail:dieter.baeurle@jku.at 相似文献
18.
É. Z. Kurmaev D. A. Zatsepin S. O. Cholakh B. Schmidt Y. Harada T. Tokushima H. Osawa S. Shin T. Takeuchi 《Physics of the Solid State》2005,47(4):754-757
The local structure of the chemical bond of iron ions implanted into SiO2 glasses (implantation energy, 100 keV; fluence, 1 × 1016 cm?2) is investigated using x-ray emission and absorption spectroscopy. The Fe L x-ray emission and absorption spectra are analyzed by comparing them with the corresponding spectra of reference samples. It is established that iron nanoparticles implanted into the SiO2 vitreous matrix are in an oxidized state. The assumption is made that the most probable mechanism of transformation of iron nanoparticles into an oxidized state during implantation involves the breaking of Si-O-Si bonds with the formation of Si-Si and Fe-O bonds. 相似文献
19.
The controllable synthesis and characterization of novel thermally stable silver-based particles are described. The experimental approach involves the design of thermally stable nanostructures by the deposition of an interfacial thick, active titania layer between the primary substrate (SiO2 particles) and the metal nanoparticles (Ag NPs), as well as the doping of Ag nanoparticles with an organic molecule (Congo Red, CR). The nanostructured particles were composed of a 330-nm silica core capped by a granular titania layer (10 to 13 nm in thickness), along with monodisperse 5 to 30 nm CR-Ag NPs deposited on top. The titania-coated support (SiO2/TiO2 particles) was shown to be chemically and thermally stable and promoted the nucleation and anchoring of CR-Ag NPs, which prevented the sintering of CR-Ag NPs when the structure was exposed to high temperatures. The thermal stability of the silver composites was examined by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Larger than 10 nm CR-Ag NPs were thermally stable up to 300 °C. Such temperature was high enough to destabilize the CR-Ag NPs due to the melting point of the CR. On the other hand, smaller than 10 nm Ag NPs were stable at temperatures up to 500 °C because of the strong metal-metal oxide binding energy. Energy dispersion X-ray spectroscopy (EDS) was carried out to qualitatively analyze the chemical stability of the structure at different temperatures which confirmed the stability of the structure and the existence of silver NPs at temperatures up to 500 °C. 相似文献
20.
Magnetic core/shell (CS) nanocomposites (MNCs) are synthesized using a simple method, in which a magnesium ferrite nanoparticle (MgFe2O4) is a core, and an amorphous silicon dioxide (silica SiO2) layer is a shell. The composition, morphology, and structure of synthesized particles are studied using X-ray diffraction, field emission electron microscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), scattering electrophoretic photometer, thermogravimetric analysis (TGA), and Mössbauer spectroscopy. It is found that the MgFe2O4/SiO2 MNC has the core/shell structure formed by the Fe?O–Si chemical bond. After coating with silica, the MgFe2O4/SiO2 MNC saturation magnetization significantly decreases in comparison with MgFe2O4 particles without a SiO2 shell. Spherical particles agglomerated from MgFe2O4 nanocrystallites ~9.6 and ~11.5 nm in size function as cores coated with SiO2 shells ~30 and ~50 nm thick, respectively. The total size of obtained CS MNCs is ~200 and 300 nm, respectively. Synthesized CS MgFe2O4/SiO2 MNCs are very promising for biomedical applications, due to the biological compatibility of silicon dioxide, its sizes, and the fact that the Curie temperature is in the region required for hyperthermal therapy, 320 K. 相似文献