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1.
Raman spectra acquired from Si
x
Ge1−x
-nanocrystal-embedded SiO2 films show dependence of the Si–Si optical phonon frequency on Si content. The frequency upshifts, and peak intensity increases
as the silicon concentration increases. For a given Si content, the frequency remains unchanged with annealing temperature.
Spectral analysis and density functional theory calculation reveal that the optical Si–Si phonon is related to the formation
of localized Si clusters surrounded by Si/Ge atomic layers in the Si
x
Ge1−x
nanocrystals and the intensity enhancement arises from the larger cluster size. The synergetic effect of surface tensile
stress and phonon confinement determines the Si–Si optical phonon behavior. 相似文献
2.
A series of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ (x=0.0–0.97, y=0.03) phosphors were synthesized by high-temperature solid-state reaction. The XRD patterns confirm the formation of a solid
solution of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+. An intense tunable green light is observed with the increasing ratio of Sr/Ca. With an increase in x, the excitation and emission spectra show a redshift and blueshift, respectively, due to large centroid shift and small Stokes
shift. The temperature dependent luminescence is also investigated in the temperature range of 77–450 K. The Huang–Rhys factor
and the thermal-quenching temperature are determined. Intense green LEDs were successfully fabricated based on the (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ phosphor and near-ultraviolet (∼395 nm) GaN/blue (460 nm) InGaN chips. All the results indicate that the solid solution (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ is a promising phosphor applicable to near-UV and blue LEDs for solid-state lighting. 相似文献
3.
T. M. Burbaev M. N. Gordeev D. N. Lobanov A. V. Novikov M. M. Rzaev N. N. Sibeldin M. L. Skorikov V. A. Tsvetkov D. V. Shepel 《JETP Letters》2010,92(5):305-309
The electron-hole liquid (EHL) in SiGe layers of Si/Si1 − x
Ge
x
/Si quantum-confinement heterostructures is discovered. It is composed of quasi-two-dimensional holes in the quantum well
formed by the SiGe layer and quasi-three-dimensional electrons, which occupy a wider region of space centered on this layer.
The densities of electrons and holes in the EHL are determined to be p
0 ≈ 8.5 × 1011 cm−2 and n
0 ≈ 4.8 × 1018 cm−3, respectively. It is demonstrated that the gas phase consists of excitons and excitonic molecules. The conditions on the
band parameters of the structure under which the formation of the EHL of this kind and biexcitons is possible are formulated. 相似文献
4.
M.?P.?Ivliev S.?I.?Raevskaya O.?Yu.?Kravchenko I.?P.?Raevski? L.?A.?Reznichenko 《Physics of the Solid State》2009,51(10):2109-2114
It is established that the Curie-Weiss temperature of Na1 − x
Li
x
NbO3 solid solutions determined by extrapolation of linear portions of the temperature dependence of the reciprocal of the permittivity
ɛ−1 from the cubic phase sharply increases with x, although the temperature of the ɛ(T) maximum decreases. It is shown in terms of a simple theoretical model that the experimentally observed change in the dielectric
properties of Na1 − x
Li
x
NbO3 is well explained under the assumption of formation of a dipole system due to the displacement of Li cations from the center
of the cubooctahedral cavity because of the significant steric misfit between the Na and Li cations. 相似文献
5.
Chin-Hsiang Chen 《Optical Review》2009,16(3):371-374
Al0.25In0.04Ga0.71N 310 nm near solar blind ultraviolet (UV) metal-insulator-semiconductor (MIS) sensors with different SiO2 cap layer thickness were successfully fabricated. With appropriate SiO2 layer thickness, the dark current of AlInGaN sensors was notably suppressed from 1.88 × 10−6 to 1.91 × 10−9 A, and the photo-generated carriers still could reach the electrodes by tunneling through the thin SiO2 layer under the illumination. It could be clearly seen that cut-off occurred at around 300/310 nm while the responses above
the bandgap were flat. 相似文献
6.
Boryakov A. V. Nikolitchev D. E. Tetelbaum D. I. Belov A. I. Ershov A. V. Mikhaylov A. N. 《Physics of the Solid State》2012,54(2):394-403
The chemical and phase compositions of silicon oxide films with self-assembled nanoclusters prepared by ion implantation of
carbon into SiO
x
(x < 2) suboxide films with subsequent annealing in a nitrogen atmosphere have been investigated using X-ray photoelectron spectroscopy
in combination with depth profiling by ion sputtering. It has been found that the relative concentration of oxygen in the
maximum of the distribution of implanted carbon atoms is decreased, whereas the relative concentration of silicon remains
almost identical over the depth in the layer containing the implanted carbon. The in-depth distributions of carbon and silicon
in different chemical states have been determined. In the regions adjacent to the layer with a maximum carbon content, the
annealing results in the formation of silicon oxide layers, which are close in composition to SiO2 and contain silicon nanocrystals, whereas the implanted layer, in addition to the SiO2 phase, contains silicon oxide species Si2+ and Si3+ with stoichiometric formulas SiO and Si2O3, respectively. The film contains carbon in the form of SiC and elemental carbon phases. The lower limit of the average size
of silicon nanoclusters has been estimated as ∼2 nm. The photoluminescence spectra of the films have been interpreted using
the obtained results. 相似文献
7.
Effects of chemical substitution in CeRu2Si2, a well-studied heavy fermion system and YbPd2Si2 have been investigated through magnetic susceptibility and x-ray diffraction in the systems CeRu
x
Si2, CeRu2−x
Os
x
Si2, CeRu2Si2−x
Ge
x
and YbPd2Si2−x
Ge
x
. Replacing silicon by germanium generates normal chemical pressure effect, namely, Ce and Yb atoms in CeRu2Si2 and YbPd2Si2 became more and less magnetic respectively. With increasing Ge concentration, CeRu2Si2−x
Ge
x
exhibits larger susceptibility at low temperature, goes to an antiferromagnetic state and finally becomes ferromagnetic.
In YbPd2Si2−x
Ge
x
, increasing Ge concentration drives Yb atoms to more divalent state. Electronic effects are more pronounced in CeRu2−x
Os
x
Si2 though CeRu2Si2 and CeOs2Si2 have very nearly the same lattice parameters. It is conjectured that CeRu2Si2−x
Ge
x
may be the first Ce-based heavy fermion having a magnetic ground state.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
8.
I. Stenger B. Gallas L. Siozade S. Fisson G. Vuye S. Chenot J. Rivory 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):176
SiOx films (1<x<2), 0.5 μm thick, have been elaborated by electron-gun evaporation. A thermal annealing of these films induced a phase separation leading to the formation of Si nanocrystals embedded in a SiO2 matrix. These films have been studied by infrared spectroscopic ellipsometry and by X-ray photoelectron spectroscopy (XPS). The effective dielectric function of the thin films has been extracted in the 600–5000 cm−1 range which allowed us to deduce the dielectric function of the matrix surrounding the Si-nc. A study of the Transverse Optical (TO) vibration mode has revealed the presence of SiOx into the matrix. Before XPS measurements, the films have been etched in fluorhydric acid to remove the superficial SiO2 layer formed during air exposure. The Si 2p core-level emission has been recorded. The decomposition of the Si 2p peak into contributions of the usual five tetrahedrons Si-(Si4−nOn) (n=0–4) has also revealed the presence of a SiOx phase. Consistency between infra-red and XPS results is discussed. 相似文献
9.
A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20)
x
(SiO
n
)100 − x
and (Co86Nb12Ta2)
x
(SiO
n
)100 − x
has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in
the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures
have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0
kJ/m3 for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites and 5–8 kJ/m3 for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites. The fundamental differences in the concentration dependences of the anisotropy constant K
eff and the coercive force H
C
have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal
phase increases, the quantities K
eff and H
C
increase for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites and decrease for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites. 相似文献
10.
L. V. Krasilnikova N. A. Baidakova M. V. Stepikhova Z. F. Krasilnik V. Yu. Chalkov V. G. Shengurov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(1):96-100
The Si/Si1 − x
Ge
x
:Er/Si heterostructures, which are of interest for laser applications, have been investigated. The types of optically active
Er3+ centers making a dominant contribution to the photoluminescence response of the structures studied are analyzed and their
relationship with the parameters of the Si1 − x
Ge
x
:Er heterolayer and the post-growth annealing conditions is shown. On the basis of the PL kinetic analysis of the structures
with an isolated type of optically active Er3+ centers, it is concluded that population inversion of Er3+ ion states can be obtained under optical pumping and the effect of nonradiative recombination channels in Si1 − x
Ge
x
:Er heterolayers on the excitation efficiency of Er centers and the conditions for population inversion is shown.
Original Russian Text ? L.V. Krasilnikova, N.A. Baidakova, M.V. Stepikhova, Z.F. Krasilnik, V.Yu. Chalkov, V.G. Shengurov,
2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 1, pp. 103–108. 相似文献
11.
The dielectric properties of the ceramics of (1 − x)BiFeO3 − x(KBi)1/2TiO3 (0.40 < x < 0.85) solid solutions with an orthorhombic structure have been studied using impedance spectroscopy in the frequency range
25–106 Hz at different temperatures. It has been shown that these solid solutions undergo a diffuse ferroelectric phase transition.
The Curie temperature is found to be in the range 620–640 K. The activation energies of dielectric polarization relaxation
(δE
M
) and dc charge carriers (ΔE
dc) are determined. It has been established that, in the vicinity of 460 K, ΔE
dc increases jumpwise as the temperature increases. 相似文献
12.
A. A. Samokhvalov T. I. Arbuzova N. A. Viglin V. V. Osipov N. I. Solin S. V. Naumov V. G. Bamburov N. I. Lobachevskaya O. G. Reznitskikh 《Physics of the Solid State》1999,41(2):262-264
Mg1−x
CuxO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg1−x
CuxO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of
5–550 K. It is shown that χ
−1(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ
eff=1.9 μ
B, close to the 1.73 μ
B of a Cu2+ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10−4 eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg1−x
CuxO at T=300 K is ≈10−11–10−12 Ω−1 cm−1 for x=0 and increases to 10−5–10−6 Ω−1 cm−1 for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg1−x
CuxO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the
structure is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999) 相似文献
13.
P. Thiyagarajan Brajesh Tiwari M. Kottaisamy N. Rama M. S. Ramachandra?Rao 《Applied Physics A: Materials Science & Processing》2009,94(3):607-612
Cool white light was realized in Y2−x−y
Gd
x
SiO5: Ce
y
phosphor under near UV excitation, due to the occupation Ce3+ in Y3+ 1st and 2nd site, synthesized using solid state carbothermal reduction route. SEM with elemental analysis show the existence
of Gd in Y2SiO5:Ce enhances the particles size in comparison to Y2SiO5:Ce phosphors alone. Gd3+ (0.00≤x≤0.75) and Ce3+ (0.02≤y≤0.10) concentration was optimized to 0.50 and 0.08 in Y2SiO5, respectively. The CIE chromaticity color coordinates (0.24, 0.20) are close to cool white light value which could be useful
for the fabrication of cool white LED. 相似文献
14.
The dielectric nonlinearity of ferroelectric Li2−x
NaxGe4O9 (x≈0.23) crystals is measured in the neighborhood of the phase transition temperatures. The magnitude of the nonlinear coefficient
β is estimated from the shift in T
c and the reduction in ɛ
max under the influence of E
=, from the dielectric nonlinearity in the paraphase, and from the temperature dependence of P
s in crystalline Li2−x
NaxGe4O9 (x≈0.23). The resulting values of β are 1.87, 1.26, 2.17, and 1.17×10−9 (CGSE cm2)−2, respectively. The mechanism for the phase transition in crystalline Li2−x
NaxGe4O9 (x≈0.23) is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 1070–1072 (June 1999) 相似文献
15.
I. N. Andryushina K. P. Andryushin O. N. Razumovskaya L. A. Shilkina L. A. Reznichenko Yu. I. Yurasov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1127-1129
The behavior of the relative permittivity ɛ/ɛ0 of PbZr1 − x
Ti
x
O3 (PZT) solid solutions (0.495 ≤ x ≤ 0.51) in the temperature range of 100–300 K at frequencies from 1 × 10−2 to 2 × 107 Hz was investigated. Diffuse, strongly relaxing maxima at T = 230−260 K (x = 0.495−0.505) and 150–160 K (x = 0.510) were observed in the PZT studied. The relaxation processes are well described by the Vogel-Fulcher law, and the
dielectric spectra are approximated by the Cole-Cole formula. 相似文献
16.
H. Lehmann G. Nimtz L. D. Haas T. Jakobus 《Applied Physics A: Materials Science & Processing》1981,25(3):291-295
The dielectric properties of epitaxial Pb1−x
Sn
x
Te layers are investigated at 9 GHz in a composition range betweenx=0 and 0.225. The samples are characterized by fairly low carrier concentrations between 1.4×1016 and 32×1016 cm−3. Data of the static dielectric constant (ε
s
) are obtained at temperatures of 77 and 300 K. The results of ε
s
are 25% to 100% higher compared to previous measurements in bulk material from other authors. The observed higher values
of ε
s
in the investigated samples may be due to the reduced number of point defects in epitaxially grown Pb1−x
Sn
x
Te layers. The model of Kawamura which predicts a dependence of ε
s
on the effective band gap cannot be verified. 相似文献
17.
Silicon MOS structures with an SiO2−Si3N4 insulator were exposed to X-rays. Positive oxide charges arise and the continuous density of fast states increases at the
Si−SiO2 interface. In addition, a single energy state develops above the middle of the energy gap atE−E
v=600 meV. Annealing measurements in dry air and H2 lead to the conclusion that the single energy level originates from a dissociated hydrogen bond in the silicon dioxide. 相似文献
18.
M. A. Lapshina M. A. Isakov D. O. Filatov S. V. Tikhonov Yu. A. Matveev A. V. Zenkevich 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):411-422
(Au, Pt)/HfO2/SiO2/n-Si(001) metal-oxide-semiconductor structures with a thin (≈0.5 nm) SiO2 layer, which is formed between HfO2 and Si during atomic layer deposition of oxide layers, have been investigated via ballistic electron emission spectroscopy.
The potential barrier heights at the (Au, Pt)/HfO2 interfaces have been determined experimentally. The peculiarities observed in the curves of dependence of the collector current
on the voltage between a scanning tunneling microscope probe and a metallic electrode are related to electron transport through
the vacancy defect region of HfO2 and the quantum-mechanical interference of electron waves arising from multiple reflections at the interfaces of the two-layer
dielectric and at the interfaces of dielectric with a substrate and a metallic electrode. 相似文献
19.
E. V. Aghababyan N. P. Harutyunyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2012,47(3):142-144
Magnetization of magnetically ordered Gd5−x
Dy
x
Si2Ge2 compounds with a partial substitution of Gd atoms by isovalent Dy atoms has been investigated. From temperature and field
dependences of Gd5−x
Dy
x
Si2Ge2 alloys with x = 0−2.0 changes of the magnetic part of entropy (ΔS
M
) of alloys are determined. It is established that ΔS
M
achieves its maximum values at different temperatures, which linearly depend on the Dy concentration, and their values are
comparable with ΔS
M
max in Gd5Si2Ge2. The obtained data allow us to conclude that the above-mentioned compounds have high magnetocaloric effect and are promising
materials for using as a combined working body of magnetic refrigerators operating in the 200–270 K range of temperatures. 相似文献
20.
A. V. Voitsekhovskii S. N. Nesmelov S. M. Dzyadukh V. S. Varavin S. A. Dvoretskii N. N. Mikhailov Yu. G. Sidorov V. V. Vasil’ev M. V. Yakushev 《Russian Physics Journal》2010,53(2):148-154
Capacitance-voltage characteristics of MIS structures based on graded band-gap heteroepitaxial HgCdTe (x = 0.22–0.23 and 0.32–0.36) with grown in situ CdTe as a passivating coating are examined. The average surface-state densities
as well as mobile- and fixed-charge densities are determined for the HgCdTe/CdTe, HgCdTe/CdTe–SiO2–Si3N4, and HgCdTe/CdTe–ZnTe systems. It is shown that grown in situ CdTe forms a fairly qualitative interface, and deposition of
additional SiO2–Si3N4 and ZnTe layers makes it possible to control the electric strength and charges in the dielectric used. 相似文献