Features and mechanisms of growth of cubic silicon carbide films on silicon

The mechanisms and specific features of the growth of silicon carbide layers through vacuum chemical epitaxy in the range of growth temperatures from 1000 to 700°C have been considered. The structure of the heterojunction formed has been studied using the results of the performed investigations of photoluminescence spectra in the near-infrared wavelength range and the data obtained from the mass spectrometric analysis. It has been found that, in the silicon layer adjacent to the 3C-SiC/Si heterojunction, the concentration of point defects significantly increases and the dislocation structure is not pronounced. According to the morphological examinations of the surface of the growing film, by analogy with the theory of thermal oxidation of silicon, the theory of carbidization of surface silicon layers has been constructed. A distinctive feature of the model under consideration is the inclusion of the counter diffusion fluxes of silicon atoms from the substrate to the surface of the structure. The growth rate of films and the activation energy of diffusion processes have been estimated. The performed experiments in combination with the developed growth model have explained the aggregates of voids observed in practice under the silicon carbide layer formed in the silicon matrix and the possibility of forming a developed surface morphology (the island growth of films) even under conditions using only one flow of hydrocarbons in the reactor.     

A theory of the origin of silicon carbide polytypes

A new theory of the origin of SiC polytypes is presented in which the observed polytypes are stabilised as equilibrium phases at the high temperatures of growth, the structures becoming frozen in on cooling. Results of first principles pseudopotential total energy calculations show that the SiC polytypes containing only bands of width 2 and 3 are nearly degenerate in energy while all other polytypes have higher energies. We develop an inter-layer interaction model to describe the energies of the polytypes. Calculations of the phonon free energies of several SiC polytypes using the valence overlap shell model are described. These calculations show that the phonon free energy gives rise to effectively long ranged interactions between the SiC layers which can stabilise a large number of ordered polytypes as equilibrium phases.     

Synthesis of silicon carbide hexagonal nanoprisms

SiC hexagonal nanoprisms have been prepared by a reaction of multiwall carbon nanotubes and Si vapor in an Astro furnace at 1450 °C for 3 h. The polytype, morphology, crystal structure of the nanoprisms were studied by X-ray powder diffraction, scanning electron microscopy and high resolution transmission electron microscopy, showing their hexagonal nanoprism shapes with a 3C-SiC single crystal structure with a diameter of about 100 nm and 2 μm in length. The photoluminescence spectrum of the nanoprisms exhibits a significant blue-shift relative to bulk 3C-SiC and other nanostructured SiC. The possible growth mechanism that controls the nanostructure formation is also analysed. PACS 42.70.Nq; 68.37.-d; 78.55.-m; 78.67.Bf; 81.07.Vb     

六方晶格基底上薄膜生长的Monte Carlo模拟研究

利用Monte Carlo（MC）方法,模拟研究了六方晶格基底上薄膜生长的初始阶段岛的形貌和岛的尺寸与薄膜覆盖度以及入射粒子沉积速率之间的关系. 结果表明在基底温度为300K时,岛的形貌主要表现为分形生长,随着薄膜覆盖度的增加,岛的分形枝簇变大,岛的数目不断减少. 在同样的温度下,随着入射粒子沉积速率的增大,薄膜表面的形貌逐步由少数聚集型岛核分布状态向众多各自独立的离散型岛核分布状态过渡. 进一步研究得出,薄膜覆盖度和入射粒子沉积速率对粒子扩散能力的影响最终导致岛的形貌发生了改变.     

Monte Carlo study of entropy for face-centered cubic Ising antiferromagnets

A face-centered cubic Ising model with nearest neighbor antiferromagnetic exchangeJ _nn in the presence of a magnetic fieldH is investigated by Monte Carlo methods. Free energy and entropy of the model are obtained by integrating the equation of state along various paths, starting at suitable reference states. It is shown that at low temperatures first-order phase transitions can be located with very good precision. At the two critical fieldsH _c1/|J _nn |=4,H _c2/|J _nn |=12 a residual ground-state entropyS(0) is found, which is estimated as aboutS(0)/k _B (ln 2)/3 in both cases.In the presence of a ferromagnetic next-nearest neighbor exchange there is no longer a nonzero entropy at the critical fields, however. ForR+J _nnn /J _nn +–1 we find the same structure of the phase diagram as qualitatively predicted by Domany et al., where lines of 3-state and 4-state Potts model-like transitions meet at a multicritical point atH=0. Some consequences of our results for interpreting the ordering of face-centered cubic binary alloys are also discussed.     

Magnetoresistance in the cubic modification of silicon carbide

The results of an investigation into the angular and field dependences of the magnetoresistance in the cubic modification of silicon carbide are presented in this paper. From an analysis of the temperature dependence of the Hall mobility of the electrons and the magnetoresistive mobility it is concluded that the magnetoresistance in the specimens under investigation is conditioned by the presence of inhomogeneities.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 90–94, May, 1977.     

Monte Carlo study of interfacial silicon suboxide layers and oxidation kinetics

A simple simulation scheme that simultaneously describes the growth kinetics of SiO₂ films at the nanometer scale and the SiO_x/Si interface dynamics (its extent, and spatial/temporal evolution) is presented. The simulation successfully applies to experimental data in the region above and below 10 nm, reproduces the Deal and Grove linear-parabolic law and the oxide growth rate enhancement in the very thin film regime (the so-called anomalous region). According to the simulation, the oxidation is governed mainly by two processes: (a) the formation of a transition suboxide layer and (b) its subsequent drift towards the silicon bulk. We found that it is the superposition of these two processes that produces the crossover from the anomalous oxidation region behavior to the linear-parabolic law.     

碳化硅中点缺陷对热传导性能影响的分子动力学研究

碳化硅(SiC)由于性能优异,已广泛应用于核技术领域.在辐照环境下,载能入射粒子可使材料中的原子偏离晶体格点位置,进而产生过饱和的空位、间隙原子、错位原子等点缺陷,这些缺陷将改变材料的热物性能,劣化材料的服役性能.因此,本文利用平衡分子动力学方法(Green-Kubo方法)采用Tersoff型势函数研究了点缺陷对立方碳化硅(β-SiC或3C-SiC)热传导性能的影响规律.研究过程中考虑的点缺陷包括:Si间隙原子(Si_Ⅰ)、Si空位(Si_Ⅴ)、Si错位原子(Si_C)、C间隙原子(C_Ⅰ)、C空位(C_Ⅴ)和C错位原子(C_Si).研究结果表明,热导率(λ)随点缺陷浓度(c)的增加而减小.在研究的点缺陷浓度范围(点缺陷与格点的比例范围为0.2%—1.6%),额外热阻率(Δ_R-R_defect-R_perfect,R=1/λ,R_defect为含缺陷材料的热阻率,R_perfec...     

Energetics of native point defects in cubic silicon carbide

In this work we present a detailed investigation of native point defects energetics in cubic SiC, using state-of-the-art first principles computational method. We find that, the carbon vacancy is the dominant defect in p-type SiC, regardless the growth conditions. Silicon and carbon antisites are the most common defects in n-type material in Si-rich and C-rich conditions respectively. Interstitial defects and silicon vacancy are less favorite from the energetic point of view. The silicon vacancy tends to transform into a carbon vacancy-antisite complex and the carbon interstitial atom prefers to pair to a carbon antisite. The dumbbell structure is the lowest-energy configuration for the isolated carbon interstitial defect, and the tetrahedral interstitial silicon is a stable structure in p-type and intrinsic conditions, while in n-type material the dumbbell configuration is the stable one. Our results suggest that, in samples grown in Si-rich stoichiometric conditions, native defects are a source of n-doping and of compositional unbalance of nominally intrinsic SiC, in accord with experimental evidence.Received: 9 January 2004, Published online: 28 May 2004PACS: 61.72.Ji Point defects (vacancies, interstitials, color centers, etc.) and defect clusters - 68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc. - 74.62.Dh Effects of crystal defects, doping and substitution     

Improvement of cubic silicon carbide crystals grown from solution

Cubic-silicon carbide crystals have been grown from carbon-rich silicon solutions using the travelling-zone method. To improve the growth process, we investigated the effect of controlling more tightly some of the growth parameters. Using such improved growth conditions, our best sample is a 12 mm diameter and 3 mm long 3C–SiC crystal. It is grown on a (0001) 2 off, 6H–SiC seed and has 111-orientation. The low amount of silicon inclusions results in a reduced internal stress, which is demonstrated by the consideration of μ-Raman spectra collected at room temperature on a large number of samples.     

Influence of silicon cluster on epitaxial growth of silicon carbide

Precursor concentration dependences of growth rate, doping concentration and surface morphology have been investigated in the epitaxial growth of 4H-SiC(0001) epilayers with horizontal hot-wall CVD system using various precursor concentrations under constant C/Si ratio. Form the experimental data it is found that silicon cluster which is formed through gas phase nucleation plays an important role in controlling the doping concentration and epitaxial growth rate of the silicon carbide. It was observed that t...     

超薄膜生长的Monte Carlo模拟研究

利用Monte Carlo(MC)方法模拟研究了薄膜生长的初始阶段岛的形貌和岛的尺寸与基底温度和入射粒子剩余能量之间的关系.模型中考虑了粒子的沉积、吸附粒子的扩散和蒸发等过程.结果表明当基底温度从200K变化到260K时,岛的形貌经历了一个从分散生长逐渐过渡到分形生长的过程,并且在较低温度(200K)下,随入射粒子剩余能量的增加,岛的形貌也经历了同样的变化过程.进一步研究证明,随着基底温度的升高或入射粒子剩余能量的增加,沉积粒子的扩散能力显著增强,从而使岛的形貌发生了改变.