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1.
A two-stage model of the capture of electrons and holes in traps in amorphous silicon nitride Si3N4 has been proposed. The electronic structure of a “Si–Si bond” intrinsic defect in Si3N4 has been calculated in the tight-binding approximation without fitting parameters. The properties of the Si–Si bond such as a giant cross section for capture of electrons and holes and a giant lifetime of trapped carriers have been explained. It has been shown that the Si–Si bond in the neutral state gives shallow levels near the bottom of the conduction band and the top of the valence band, which have a large cross section for capture. The capture of an electron or a hole on this bond is accompanied by the shift of shallow levels by 1.4–1.5 eV to the band gap owing to the polaron effect and a change in the localization region of valence electrons of atoms of the Si–Si bond. The calculations have been proposed with a new method for parameterizing the matrix elements of the tightbinding Hamiltonian taking into account a change in the localization region of valence electrons of an isolated atom incorporated into a solid.  相似文献   

2.
纳米非晶氮化硅键态结构的X射线径向分布函数研究   总被引:13,自引:1,他引:12       下载免费PDF全文
蔡树芝  牟季美  张立德  程本培 《物理学报》1992,41(10):1620-1626
本文用X射线径向分布函数法研究了室温到1000℃不同退火条件下的纳米非晶氮化硅样品的微结构和键合特征。观察到占庞大体积百分数界面不是“gas-like”结构,而是与非晶纳米粒子不同的新的短程序结构。Si—N键长和最近邻原子配位数(CN)均比传统Si3N4小,并存在大量的Si悬键和不饱和键。纳米氮化硅与传统Si3N4饱和共价键不同,是含有大量非饱和键和悬键的非典型共价键结构。由于键配位的不饱和特征,纳米非晶氮化硅的分子式应写作Si3-xN4-y。纳米非晶氮化硅出现强极性与非饱和键和悬键有密切的关系。 关键词:  相似文献   

3.
Charge transfer ΔQ = 0.35e at the Si-N bond in silicon nitride is determined experimentally using photoelectron spectroscopy, and the ionic formula of silicon nitride Si3+1.4N4−1.05 is derived. The electronic structure of α-Si3N4 is studied ab initio using the density functional method. The results of calculations (partial density of states) are compared with experimental data on X-ray emission spectroscopy of amorphous Si3N4. The electronic structure of the valence band of amorphous Si3N4 is studied using synchrotron radiation at different excitation energies. The electron and hole effective masses m e *m h * ≈ 0.5m e are estimated theoretically. The calculated values correspond to experimental results on injection of electrons and holes into silicon nitride.  相似文献   

4.
This paper reports that amorphous silicon nitride (a-SiNx) overcoats were deposited at room temperature by microwave ECR plasma enhanced unbalanced magnetron sputtering. The 2 nm a-SiNx overcoat has better anti-corrosion properties than that of reference a-CNx overcoats (2-4.5 nm). The superior anti-corrosion performance is attributed to its stoichiometric bond structure, where 94.8% Si atoms form Si-N asymmetric stretching vibration bonds. The N/Si ratio is 1.33 as in the stoichiometry of Si3N4 and corresponds to the highest hardness of 25.0 GPa. The surface is atomically smooth with RMS < 0.2 nm. The ultra-thin a-SiNx overcoats are promising for hard disks and read/write heads protective coatings.  相似文献   

5.
The low-energy structures of Al8Sim (m = 1–6) have been determined by using the genetic algorithm combined with density functional theory and the Second-order Moller-Plesset perturbation theory (MP2) models. The results show that the close-packed structures are preferable in energy for Al–Si clusters and in most cases there exist a few isomers with close energies. The valence molecular orbitals, the orbital level structures and the electron localisation function (ELF) consistently demonstrate that the electronic structures of Al–Si clusters can be described by the jellium model. Al8Si4 corresponds to a magic number structure with pronounced stability and large energy gap; the 40 valence electrons form closed 1S21P61D102S21F142P6 shells. The ELF attractors also suggest weak covalent Si–Si, Si–Al and Al–Al bonding, and doping Si in aluminium clusters promotes the covalent interaction between Al atoms.  相似文献   

6.
A. Bahari  Z.S. Li 《Surface science》2006,600(15):2966-2971
The growth of ultrathin films of Si3N4 directly on Si surfaces is studied with valence band photoemission. The information from these studies about the growth mechanism and the changes of the electronic structure is enhanced by the use of various photon energies with synchrotron radiation. The silicon nitride films are grown isothermally on the Si(1 0 0) and Si(1 1 1) surfaces by reactions with atomic N. The atomic nitrogen is produced by using a remote, microwave excited nitrogen plasma. The growth under these conditions was earlier shown to be self limiting. The details in the valence band spectra are identified and resolved with numerical methods, and followed systematically during the growth. Thus the identification of Si surface states, Si-nitride interface states and bulk nitride states becomes possible. The previously obtained separation between amorphous and crystalline growth occurring around 500 °C is further supported in the present studies.  相似文献   

7.
Ali Dogan 《哲学杂志》2016,96(5):459-472
In this work, viscosities of ternary Au–Ag–Cu and Al–Cu–Si liquid alloys have been calculated as a function of gold, aluminium and copper compositions for the sections Au–Ag–Cu (xAg/xCu = 0.543 at 1373 K), Alx(Cu50–Si50)(1–x) and Cux(Al50–Si50)(1–x) at 1375 K using Chou’s general solution model, Muggianu, Kohler, Toop, Hillert, Budai et al., Kozlov et al., Schick et al. and Kaptay et al. models. The present study finds that a comparison of the predicted values of viscosities associated with the geometric and physical models indicate good mutual agreement. The Muggianu model indicates the best agreement with the results obtained for Au–Ag–Cu and Alx–Cu50–Si50 alloy systems and the Kaptay et al. model, which is a physical model, indicates the best agreement with the results obtained for Al50–Cux–Si50.  相似文献   

8.
ABSTRACT

Crystalline silicon oxy-nitride (SiON) composite films are deposited on Si substrate for multiple (5, 15, 25 and 50) focus shots (FS) by plasma focus device. The X-rays diffraction patterns reveal the development of various diffraction peaks related to Si, Si3N4, and SiO2 phases which confirms the formation of SiON composite film. The intensity of Si3N4 (1 0 2) plane is linearly increased with the increase of FS. The Si3N4 (1 0 2) phase does not nucleate for 5 FS. Raman analysis confirms the formation of β–Si–N phase. Raman and Fourier transform infrared spectroscopy analysis reveals that the strength of chemical bonds like Si–N, Si–O formed during the deposition process of SiON composite films is associated with the bonds intensity which in turn depends on the number of FS. The field emission scanning electron microscopic analysis reveals that the surface morphology like size, shape and distribution of micro/nano-dimensional particles, film compactness and the formation of micro-rods, micro-teethes and micro-tubes of SiON composite films is entirely associated with the rise in substrate surface transient temperature which in turn depends on the increasing number of FS. The EDX spectrum confirms the presence of Si (22.5?±?4.7 at. %), N (13.4?±?4.5 at. %) and O (54.7?±?11.3 at. %) in the SiON composite film. The thickness of SiON composite film deposited for 50 FS is found to ~15.47?µm.  相似文献   

9.
The self-sputtering processes of (111) Si and Al surfaces under bombardment by Si N and Al N ions and clusters (N = 1−60) with the same energy per particle-projectile atom (1 keV/atom) are studied in this paper. The nonlinear effects produced in the target during the development stage of an atomic-collision cascade and during the postcascade stage are analyzed, and a correlation between these effects and secondary emission characteristics is found. The study has been carried out in the framework of classical molecular dynamics. As a result, a number of features of (111) Si and Al surface sputtering and erosion have been revealed. Thus, it has been established that the sputtering yield increases nonadditively as the size N of the implanted cluster increases at N > 10, which is related to the appearance of nonlinear cascades and the postcascade heat spike, and is accompanied by microcrater formation. It is shown that the implantation of clusters into the Si target leads to the formation of amorphous regions.  相似文献   

10.
11.
Ultra thin films of pure silicon nitride were grown on a Si (1 1 1) surface by exposing the surface to radio-frequency (RF) nitrogen plasma with a high content of nitrogen atoms. The effect of annealing of silicon nitride surface was investigated with core-level photoelectron spectroscopy. The Si 2p photoelectron spectra reveals a characteristic series of components for the Si species, not only in stoichiometric Si3N4 (Si4+) but also in the intermediate nitridation states with one (Si1+) or three (Si3+) nitrogen nearest neighbors. The Si 2p core-level shifts for the Si1+, Si3+, and Si4+ components are determined to be 0.64, 2.20, and 3.05 eV, respectively. In annealed sample it has been observed that the Si4+ component in the Si 2p spectra is significantly improved, which clearly indicates the crystalline nature of silicon nitride. The high resolution X-ray diffraction (HRXRD), scanning electron microscopy (SEM) and photoluminescence (PL) studies showed a significant improvement of the crystalline qualities and enhancement of the optical properties of GaN grown on the stoichiometric Si3N4 by molecular beam epitaxy (MBE).  相似文献   

12.
傅广生  于威  王淑芳  李晓苇  张连水  韩理 《物理学报》2001,50(11):2263-2268
利用直流辉光放电等离子体辅助的脉冲激光沉积技术在Si衬底上生长了碳氮薄膜.通过扫描电子显微镜、X射线衍射、X射线光电子能谱、俄歇电子能谱等多种手段,对薄膜的形貌、成分、晶体结构、价键状态等特性进行了分析和确定.结果表明,沉积薄膜为含有非晶SiN和晶态氮化碳颗粒结构,晶态成分呈多晶态,主要为α-C3N4相、β-C3N4相,晶粒大小为40—60nm.碳氮之间主要以C-N非极性共价键形式相结合. 关键词: 脉冲激光沉积 直流辉光放电 碳氮薄膜  相似文献   

13.
The morphology of the tracks of swift ions revealed in amorphous silicon nitride after treatment in an HF solution is studied. The Si3N4/Si structures were irradiated with Fe, Kr, and W ions in the electron energy loss regime. Discontinuous tracks were recorded upon exposure to W only, with an electron energy loss of 20.4 keV nm−1 being maximal for the conditions of our experiment. The results from calculations of the track formation in Si3N4 based on the thermal spike model are presented.  相似文献   

14.
Si3N4/Si表面Si生长过程的扫描隧道显微镜研究   总被引:1,自引:0,他引:1       下载免费PDF全文
汪雷  唐景昌  王学森 《物理学报》2001,50(3):517-522
利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si3N4/Si(111)和Si3N4/Si(100)表面生长过程的结构演变.在生长早期T为350—1075K范围内,Si在两种衬底表面上都形成高密度的三维纳米团簇,这些团簇的大小均在几个纳米范围内,并且在高温退火时保持相当稳定的形状而不相互融合.当生长继续时,Si的晶体小面开始显现.在晶态的Si3N4(0001)/S 关键词: 氮化硅 扫描隧道显微镜 纳米颗粒  相似文献   

15.
Using the photoluminescence surface state spectroscopy (PLS3) technique, attempts were made to determine the surface state density (Nss) distribution on AlxGa1−xAs (x≈0.3) surfaces passivated by the Si interface control layer (ICL) technique. Air-exposed AlGaAs epitaxial wafers which are technologically important for fabrication of various devices were passivated ex situ by forming a SiO2/Si3N4/Si ICL/AlGaAs structure after the HCl treatment and their photoluminescence behavior was investigated in detail. The result of the PLS3 analysis indicated that Si ICL-based passivation reduces the minimum interface state density value down to 1010 cm−2 eV−1 range. Some indication was also obtained that further improvements are possible by using electron cyclotron resonance (ECR)-enhanced N2 plasma for Si3N4/Si ICL interface formation.  相似文献   

16.
We compare 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra from the two modifications of silicon nitride, α-Si3N4 and β-Si3N4, with that of a fully (29Si, 15N)-enriched sample 29Si315N4, as well as 15N NMR spectra of Si315N4 (having 29Si at natural abundance) and 29Si315N4. We show that the 15N NMR peak-widths from the latter are dominated by J(29Si–15N) through-bond interactions, leading to significantly broader NMR signals compared to those of Si315N4. By fitting calculated 29Si NMR spectra to experimental ones, we obtained an estimated coupling constant J(29Si–15N) of 20 Hz. We provide 29Si spin-lattice (T1) relaxation data for the 29Si315N4 sample and chemical shift anisotropy results for the 29Si site of β-Si3N4. Various factors potentially contributing to the 29Si and 15N NMR peak-widths of the various silicon nitride specimens are discussed. We also provide powder X-ray diffraction (XRD) and mass spectrometry data of the samples.  相似文献   

17.
Volodin  V. A.  Timofeev  V. A.  Nikiforov  A. I.  Stoffel  M.  Rinnert  H.  Vergnat  M. 《JETP Letters》2019,109(6):368-371

Multilayer heterostructures Si/Si1−xSnx grown by molecular beam epitaxy on Si (001) substrates have been studied by Raman and photoluminescence spectroscopy. Raman spectra exhibit peaks corresponding to the vibrations of Si-Sn and Sn-Sn bonds; the vibrations of Sn-Sn bonds imply the presence of tin nanocrystals in heterostructures. Two photoluminescence bands at 0.75 eV (1650 nm) and 0.65 eV (1900 nm) have been observed in heterostructures at low temperatures. The former band can be attributed to optical transitions in quantum wells in the type II heterostructure Si/Si1−xSnx. The latter band can be associated with excitons localized in tin nanocrystals.

  相似文献   

18.
Nanostructured Si exhibits superior photothermal performance and is a cost-effective solar absorbing material for solar evaporation, photothermal catalysis, and solar power systems. Defects are effective nonradiative recombination centers and are suppressed in amorphous silicon (a-Si) to benefit radiative recombination. In this research, a bottom-up approach to optimize the disordered and defective structure of non-hydrogenated a-Si by magnetron sputtering for photothermal conversion is proposed. The 2D mesoporous structure is developed in a-Si thin films under the growth scenario with reduced nucleation density. Local disorder and defects are analyzed based on the vibrational response of Si-Si bonds. Accompanied by narrowed bandgap (Eg) of 1.06 eV (Eu) and elongated Urbach tail of 0.49 eV, prominent short-range disorder and substantial amounts of dangling bonds contribute to enhanced solar absorption. Thereby, the full-spectrum absorptance above 92% can be realized with antireflection coatings of SiO2/Si3N4. The electron–phonon behavior revealed by resonance Raman scattering provides a comparative study on phonon production. Stronger electron–phonon coupling originated from the defective structure can be achieved at larger Eu. Provided with narrowed Eg and elongated Eu, local disorder and coordinative defects benefit both broadband absorption and thermal production, which can be introduced with controlled nucleation density and arrival rates.  相似文献   

19.
详细论述Si/SiGe量子级联激光器的工作原理,通过对比找到一组合适的Si,Ge和SiGe合金的能带参数,进而应用6×6 k·p方法计算了不同阱宽、不同Ge组分Si/Si1-xGex/Si量子阱价带量子化的空穴能级本征值及其色散关系,分析Si/Si1-xGex/Si量子阱空穴态能级间距随阱宽和组分的变化规律,最后应用计算结果讨论了Si/SiGe量子级联激光器有源区的能带设计,有益于优化Si /SiGe量子级联激光器结构. 关键词: 硅锗材料 量子级联激光器 子带跃迁 k·p方法')" href="#">k·p方法  相似文献   

20.
The present work reports the SEM, EPMA and TEM examination of reactions at the interface of Al7075 alloy and a 50/50 wt% mixture of BaAl2Si2O8 + CaAl2Si2O8 feldspars at 850 °C, 1150 °C and 1250 °C. Sintering of the feldspar mixture at 1450 °C caused dissolution of ~1.0 wt% Ca in BaAl2Si2O8 and 0.5 wt% Ba in CaAl2Si2O8. The interaction of the Al alloy with the sintered feldspars shifted the alloy composition to the Al–Si–αBaAl2Si2 and Al–Si–βaAl2Si2 compatibility triangles. The feldspars underwent a series of phase transformations, leading ultimately to the formation of Al2O3.  相似文献   

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