共查询到20条相似文献,搜索用时 15 毫秒
1.
S. A. Grudinkin S. A. Kukushkin A. V. Osipov N. A. Feoktistov 《Physics of the Solid State》2017,59(12):2430-2435
Using infrared (IR) spectroscopy and spectral ellipsometry, we experimentally confirmed the previously predicted mechanochemical effect of the stoichiometric composition disorder leading to the formation of carbon-vacancy structures in silicon carbide (SiC) films grown on silicon substrates by the atom substitution method. It was found that a band at 960 cm–1 in the IR spectra of SiC films on silicon, corresponding to “carbon-vacancy clusters” is always present in SiC films grown under pure carbon monoxide (CO) or in a mixture of CO with silane (SiH4) on Si substrates of different orientation and doping level and type. There is no absorption band in the region of 960 cm–1 in the IR spectra of SiC films synthesized at the optimum ratio of the CO and trichlorosilane (SiHCl3) gas pressures. The previously predicted mechanism of the chemical reaction of substitution of Si atoms for carbon by the interaction of gases CO and SiHCl3 on the surface of the silicon substrate, which leads to the formation of epitaxial layers of single-crystal SiC, is experimentally confirmed. 相似文献
2.
Methods of linear algebra were used to find a basis of independent chemical reactions in the topochemical conversion of silicon into silicon carbide by the reaction with carbon monoxide. The pressure–flow phase diagram was calculated from this basis, describing the composition of the solid phase for a particular design of vacuum furnace. It was demonstrated that to grow pure silicon carbide, it is necessary to ensure the pressure of carbon monoxide less than a certain value and its flow more than a certain value, depending on the temperature of the process. The elastic fields around vacancies formed were considered for the first time in calculating the topochemical reaction. It was shown that the anisotropy of these fields in a cubic crystal increases the constant of the main reaction approximately fourfold. 相似文献
3.
Silicon carbide samples synthesized from silicon by topochemical substitution of atoms are studied by the ion channeling method. The results of the analysis unambiguously demonstrate the occurrence of structural heteroepitaxy. The lattice of synthesized silicon carbide of hexagonal polytype 6H is epitaxially matched in the 〈0001〉 direction with the lattice grating grid array network of an initial substrate silicon in the 〈111〉 direction. The main features of structural self-coupling matching in this epitaxial heterocomposite are revealed. Despite the very large silicon carbide and silicon lattice parameter mismatch, the misfit dislocation density at the interface is low, which is a feature of the topochemical substitution method leading to comparable structures. 相似文献
4.
Molecular-mechanical and semiempirical quantum-mechanical methods have been applied to simulate and calculate a geometrically
optimized structure of clusters of polymorphic types of silicon carbide, and their structural parameters and some properties
(densities, sublimation energies) have been determined. A classification of silicon carbide phases has been proposed, which
shows the possible existence of twenty one SiC phases whose atoms are at crystallographically equivalent sites. The structures
of seventeen proposed silicon carbide phases have been described and studied for silicon carbide for the first time. 相似文献
5.
Physics of the Solid State - The interaction between a silicon vacancy and a carbon atom formed in silicon during the topochemical synthesis of silicon carbide from silicon has been calculated... 相似文献
6.
A. S. Poplavnoi 《Russian Physics Journal》2008,51(7):692-700
A method is presented for investigation into the symmetry of phonon spectra of complex compounds composed of the Bravais sublattices.
It is shown that quasi-degeneracy in the phonon spectra of crystals containing sublattices with the symmetry higher than that
of the crystallographic group of the compound results from this high symmetry. The mechanism responsible for the translational
quasi-degeneracy has peculiar features for various structures. For substitution structures in a highly symmetrical lattice,
the translational quasi-degeneracy is caused by convolution of the total phonon spectrum of the highly symmetrical structure.
The convolution of the phonon spectra in crystals containing sublattices of different Bravais types occurs separately for
each sublattice. Quasi-degeneracy also occurs in the compounds containing sublattices whose point symmetry is higher than
that of the crystal structure. The method is illustrated by the example of a one-dimensional structure containing sublattices.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–38, July, 2008. 相似文献
7.
C.Q. Chen R. Helbig F. Engelbrecht J. Zeman 《Applied Physics A: Materials Science & Processing》2001,72(6):717-720
We performed infrared absorption measurements on 4H-SiC samples with polarization E∥c and E⊥c at 8, 85 and 300 K. From the
strong temperature dependence of the absorption lines, electronic transitions are separated from vibronic transitions. The
electronic transition lines between 300 and 500 cm-1 are assigned to the shallow nitrogen donor. It is found that the electronic transitions of the shallow nitrogen donor are
polarization dependent. Zeeman spectroscopy was performed to study the influence of the magnetic field on the electronic transitions
up to 15 T. The results show no linear Zeeman splitting and only a diamagnetic shift. This is consistent with the effective
mass tensor of three different diagonal components in 4H-SiC.
Received: 25 November 1999 / Accepted: 20 April 2000 / Published online: 2 August 2000 相似文献
8.
Phonon conductivity in intermediately doped n-type silicon still remains unexplained. In this paper we have calculated the
phonon conductivity in Li-doped silicon for Nex < Nc using Mikoshiba's inhomogeneity model. We have introduced spherical polar coordinates for the phonon polarization vectors
in Sota and Suzuki's theory in order to take into account the realistic picture of the scattered phonons. Deformation potential
for different polarizations λ has been evaluated for the metallic region. Present calculations show that Mikoshiba's inhomogeneity
model is able to explain the phonon conductivity of Li-doped silicon having intermediate donor concentration very well.
Received 18 May 2001 / Received in final form 4 July 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: mkroy@ctgu.edu 相似文献
9.
10.
Photoluminescent (PL) p-type 6H porous silicon carbides (PSCs), which showed a strong blue-green photoluminescence band centered at approximately 490 nm, were annealed in Ar and vacuum conditions. The morphological, optical, and chemical states after annealing are reported on electrochemically etched SiC semiconductors.The thermal treatments in the Ar and vacuum environments showed different trends in the PL spectra of the PSC. In particular, in the case of annealing in a vacuum, the PL spectra showed both a weak red PL peak near 630 nm and a relatively intense PL peak at around 430 nm in the violet region. SEM images showed that the etched surface had spherical nanostructures, mesostructures, and islands. With increasing annealing temperature it changes all spherical nanostructures. The average pore size observed at the surface of the PSC before annealing was of the order of approximately 10 nm.In order to investigate the surface of a series of samples in detail, both the detection of a particular chemical species and the electronic environments at the surface are examined using X-ray photoelectron spectroscopy (XPS). The chemical states from each XPS spectrum depend differently before and after annealing the surface at various temperatures. From these results, the PL spectra could be attributed not only to the quantum size effects but also to the oxide state. 相似文献
11.
Formation of the intermediate semiconductor larger for the Ohmic contact to silicon carbide using Germanium implantation 下载免费PDF全文
By formation of an intermediate semiconductor layer (ISL) with a
narrow band gap at the metallic contact/SiC interface, this paper
realises a new method to fabricate the low-resistance Ohmic contacts
for SiC. An array of transfer length method (TLM) test patterns is
formed on N-wells created by P+ ion implantation into
Si-faced p-type 4H-SiC epilayer. The ISL of nickel-metal Ohmic
contacts to n-type 4H-SiC could be formed by using Germanium ion
implantation into SiC. The specific contact resistance ρc as low as 4.23× 10-5~Ωega \cdotcm2 is
achieved after annealing in N2 at 800~°C for 3~min,
which is much lower than that (>900~°C) in the typical SiC
metallisation process. The sheet resistance Rsh of the
implanted layers is 1.5~kΩega /\Box. The technique for
converting photoresist into nanocrystalline graphite is used to
protect the SiC surface in the annealing after Ge+ ion
implantations. 相似文献
12.
The surface optical or Fuchs-Kliewer phonons of the (0 0 1) surface of 3C-SiC and the Si-terminated (0 0 0 1) surfaces of 4H- and 6H-SiC have been investigated with high resolution electron energy loss spectroscopy (HREELS). For each of the SiC polytypes the frequency of the surface optical phonon changes with surface reconstruction, indicating subtle differences in the static polarization at differently reconstructed surfaces. Due to their anisotropy, hexagonal surfaces exhibit a second, much weaker Fuchs-Kliewer mode. For all surfaces under examination, a linear dispersion of the Fuchs-Kliewer mode frequency has been found for wave vectors close to the -point. This dispersion can be explained by dynamical dipole coupling between atomic oscillators at the surface of the highly polar silicon carbide. 相似文献
13.
V. A. Solodukha A. S. Turtsevich Ya. A. Solovyev O. E. Sarychev S. V. Gaponenko O. V. Milchanin 《Journal of Applied Spectroscopy》2013,79(6):1002-1005
We have demonstrated the effectiveness of Raman spectroscopy for monitoring nickel silicide formation processes on the surface of silicon wafers, with deposition of a composite metal layer (nickel, platinum, and vanadium) under industrial process conditions in microelectronics. The observed shift of all the NiSi lines toward lower energies is associated with formation of the metastable silicide phase Ni1?x Pt x Si, which leads to the presence of stresses in the lattice as a result of the increase in the distances between atoms. 相似文献
14.
Evolution of infrared spectra and optical emission spectra in hydrogenated silicon thin films prepared by VHF-PECVD 下载免费PDF全文
A series of hydrogenated silicon thin films with varying silane concentrations have been deposited by using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The deposition process and the silicon thin films are studied by using optical emission spectroscopy (OES) and Fourier transfer infrared (FTIR) spectroscopy, respectively. The results show that when the silane concentration changes from 10% to 1%, the peak frequency of the Si—H stretching mode shifts from 2000 cm - 1 to 2100 cm - 1, while the peak frequency of the Si—H wagging—rocking mode shifts from 650 cm - 1 to 620 cm - 1. At the same time the SiH*/Hα intensity ratio in the plasma decreases gradually. The evolution of the infrared spectra and the optical emission spectra demonstrates a morphological phase transition from amorphous silicon (a-Si:H) to microcrystalline silicon (μc-Si:H). The structural evolution and the μc-Si:H formation have been analyzed based on the variation of Hα and SiH* intensities in the plasma. The role of oxygen impurity during the plasma process and in the silicon films is also discussed in this study. 相似文献
15.
The nonadiabatic corrections to the self-energy part Σs(q, ω) of the phonon Green’s function are studied for various values of the phonon vectors q resulting from electron-phonon interactions. It is shown that the long-range electron-electron Coulomb interaction has no
direct influence on these effects, aside from a possible renormalization of the corresponding constants. The electronic response
functions and Σs(q, ω) are calculated for arbitrary vectors qand energy ω in the BCS approximation. The results obtained for q=0 agree with previously obtained results. It is shown that for large wave numbers q, vertex corrections are negligible and Σs(q, ω) possesses a logarithmic singularity at ω=2Δ, where Δ is the superconducting gap. It is also shown that in systems with nesting, Σs(Q, ω) (where Q is the nesting vector) possesses a square-root singularity at ω=2Δ, i.e., exactly of the same type as at q=0. The results are used to explain the recently published experimental data on phonon anomalies, observed in nickel borocarbides
in the superconducting state, at large q. It is shown, specifically, that in these systems nesting must be taken into account in order to account for the emergence
of a narrow additional line in the phonon spectral function S(q, ω)≈−π
−1 Im D
s
(q, ω), where D
s
(q, ω) is the phonon Green’s function, at temperatures T<T
c
.
Zh. éksp. Teor. Fiz. 115, 1799–1817 (May 1999) 相似文献
16.
A previously proposed five parameter phenomenological screened shell model for the lattice dynamics of cubic metals is applied to compute the phonon frequencies of copper in the off-symmetry directions. The theoretical results are compared with the experimental findings for the first time. It has been pointed out that a model which gives excellent results in the symmetry directions may not necessarily reproduce similar results in the off-symmetry directions. 相似文献
17.
18.
Optical properties of porous A
3
B
5 semiconductors (GaAs, InP, and GaP) in the far-infrared region, in particular, the specular reflection and attenuated total
reflection, including the excitation regime of surface polaritons, are considered. Considering a porous material as a composite,
we performed calculations in the context of the effective medium model using two modifications of it, Maxwell-Garnett and
Bruggeman, which correspond to two different topologies of the composite material—matrix and statistical. The effect of porosity
of the material and of such parameters as doping, anisotropy, and penetration depth of an electromagnetic wave to a porous
material on optical spectra is analyzed. In addition, some experimental data are presented and the adequacy of the performed
numerical simulation is demonstrated. 相似文献
19.
V. A. Karachinov 《Technical Physics》1998,43(7):868-869
Experiments are described which show that under pulsed thermal loading conditions, a damaged layer is formed in SiC which
inherits the typical erosion defects (craters, chips, microcracks).
Zh. Tekh. Fiz. 68, 133–135 (July 1998) 相似文献
20.
M. E. Kompan I. G. Aksyanov I. V. Kul’kova S. A. Kukushkin A. V. Osipov N. A. Feoktistov 《Physics of the Solid State》2009,51(12):2469-2473
The luminescence spectra of silicon carbide films grown on silicon by solid-state epitaxy have been studied. It has been shown
that, depending on the growth conditions, one can obtain films of different SiC polytypes, including the cubic and hexagonal
ones. In many cases, the films thus grown display a mixture of various polytypes, but it is possible to prepare films of predominantly
hexagonal symmetry (the coexistence of the 4H and 2H hexagonal phases, which are close in properties, is also possible). It thus has been demonstrated that the silicon carbide
films grown on silicon by solid-state epitaxy are promising for application as damping layers in fabrication of wide-band-gap
hexagonal semiconductors on silicon substrates. 相似文献