Silicon with Magnetic Nanoclusters of Manganese Atoms as a New Ferromagnetic Material

Technical Physics - Photosensitivity of the negative magnetoresistance (NMR) of silicon containing magnetic nanoclusters of manganese atoms is revealed under background and IR (up to λ = 3...     

介质阻挡放电氢等离子体中氢原子浓度的光谱诊断

在化学气相沉积功能材料等离子体刻蚀及表面处理等过程中, 氢原子起着非常重要的作用。文章详细论述了利用发射光谱技术诊断氢原子的基本原理,以氩气作为内标对介质阻挡放电氢等离子体中的氢原子浓度进行了定量的诊断,研究了氢原子浓度、氢分子解离率随气压的变化规律。发现在0.32到5.1 kPa气压范围内,氢分子的解离率由5.2%下降到0.089%,相应的氢原子浓度由4.9×1015·cm-3下降到1.3×1015·cm-3。文章还研究了氢Balmer系以及氩(750.4 nm)谱线的发射强度随气压、放电电压、频率等放电参数的变化规律。     

Dielectric Function and Diffusivity of Nonideal Plasmas

The dielectric function for a two-component (hydrogen) plasma at arbitrary degeneracies is considered in the entire (k, w)-space. Collisions are treated in Born approximation leading to a (k, w)-dependent collision integral. Two possible limits are considered: (1) k → 0 (first), w → 0 (second) leading to the dc conductivity σ. (2) w → 0 (first), k → 0 (second) leading to the diffusivity D. The relation between σ and D is discussed.     

Engineering Cubic Silicon Carbide Surfaces Properties Using Hydrogen: Metallization versus Passivation

Atomic (H) and molecular (H₂) hydrogen interaction onto the Si-rich β-SiC(100) 3×2 and Si-terminated β-SiC(100) c(4×2) surface reconstruction is investigatedabytom-resolved scanning tunneling microscopy and spectroscopy, core level and valence band photoemission spectroscopies, and infrared absorption spectroscopy. In this review, the most recent investigations are presented and discussed in the framework of existing models including the following issues: i) molecular H₂ interaction with Si rich 3×2 and ii) Si-terminated c(4×2) surface reconstructions, and iii) atomic H-induced β-SiC(100) 3×2 surface metallization. While the β-SiC(100)3×2 surface is totally inert to molecular hydrogen, the β-SiC(100) c(4×2) is instead very reactive with sticking probabilities eight orders of magnitude above those of silicon surfaces, leading to a 2×1 surface transformation and allowing to built Si atomic lines on a H-passivated β-SiC(100) surface. Contrary to its well-known role in semiconductor surface passivation, atomic H is found to metallize the β-SiC(100) 3×2 surface, which is the first example of H-induced semiconductor surface metallization. Interestingly, such a metallization is not removed by oxygen and also takes place on a pre-oxidized surface. Such an unexpected and unprecedented behavior results from the competition between H termination of top surface dangling bonds and H-induced asymmetric attack of the Si-dimers located below the surface (3^rd plane), leading to charge transfer and to metallization. PACS 68.47.GH; 73.20.-R; 79.60.-i; 81.65.-b     

Dipole Moment Function of Hydrogen Halides

A new semi-empirical method for constructing the dipole moments of diatomic molecules as functions of the internuclear distance R $\varepsilon$ [0, ∞) is suggested. The dipole moment is described by a piecewise continuous function specified by a power-law polynomial with the asymptotic μ(R) → R ³ for small R, the dipole moment and its derivatives for equilibrium positions of nuclei in the molecule, and the results of ab initio calculations of the dipole moment for large R. The method is hydrogen halide molecules.     

Calculation of Dielectric Function of a Quark-Gluon Plasma

With the hard thermal loop （HTL） resummation technique, we calculate the dielectric function excited by hard gluon in quark-gluon plasma （QCP）. We find that in a section of the space-like region po/p ∈ [0.78, 0.95], there are two extremum structures on the dielectric function curve, while the dielectric function in the HTL approximation decreases monotonously without these properties. Through the analyses of the imaginary part of the dielectric function, we conclude that the character of the dielectric function in this region reflects effects of the Landau damping.     

Structure Sensitive Reaction Channels of Molecular Hydrogen on Silicon Surfaces

The ability of the Si(001) surface to adsorb H2 molecules dissociatively increases by orders of magnitude when appropriate surface dangling bonds are terminated by H atoms. Through molecular beam techniques the energy dependent sticking probability at different adsorption sites on H-precovered and stepped surfaces is measured to obtain information about the barriers to adsorption, which decrease systematically with an increase in coadsorbed H atoms. With the help of density functional calculations for interdimer adsorption pathways, this effect is traced back to the electronic structure of the different adsorption sites and its interplay with local lattice distortions.     

Complex Response Function of Whispering Gallery Dielectric Resonators

A whispering gallery resonator coupled to a dielectric waveguide is experimentally investigated around 86 GHz using a vectorial network analyzer. The resulting complex response function is compared with a theoretical model, simplified assuming negligible stationary waves; indeed their presence can be effectively compensated by a proper normalization procedure, made possible by a suitable analysis in the complex field. It is demonstrated that the proposed approach well reproduce the experimental results in a wide range of coupling conditions. Moreover, some outcomes of the model concerning the power flowing into the resonator are briefly discussed.     

The Role of Silicon Oxide Layers in Luminescence of Ensembles of Silicon Quantum Dots

Based on the quantum confinement-luminesecence center model,to ensembles of spherical silicon nanocrystals (nc-Si)containg two kinds of luminescence centers(LCs) in the SiOx layers surrounding the nc-Si,the relationship between the photolumincescence(PL) and the thickness of the SiOx layer is studied with the excitation energy flux density as a parameter.When there is no SiOx layer surrounding the nc-Si,the electron-heavy hole pair can only recombine inside the nc-Si,then the PL bluehift with reducing particle sizes roughly accords with the rule predicted by the quantum confinement model of Canham.When there presences a SiOx layer,some of the carriers may tunnel into it and recombine outside the nc-Si at the LCs to emit visible light.The thicker the SiOx layer is,the higher the radiative recombination rate occurred outside the nc-Si will be.When the central Scale of the nc-Si is much smaller than the critical scale,the radiative recombination rate outside the nc-Si dominates,and visible PL will be possible for some nc-Si samples with big average radius,greater than 4nm,for example.When there is only one kind of LC in the SIOx layer,the PL peak position does not shift with reducing particle sizes.All these conclusions are in accord with the experimental results.When there are two or more kinds of LCs in the SiOx layer,the PL peak position energy and intensity swing with reducing particle sizes.     

矩形介质光波导的条形传递函数方法

将条形传递函数方法引入矩形介质光波导传播特性的分析计算,从标量波动方程的变分表达式出发,推导和建立了条形传递函数方法的基本方程和两种应用模型,作为算例,给出了阶跃型折射率分布矩形介质光波导的数值计算结果,并与其它方法进行了比较,表明了此方法的精度及对光波导问题的适用性。     

多孔二氧化硅玻璃的有效介电函数

本文研究了具有７．５ｎｍ孔隙的多孔二氧化硅玻璃的介电函数与孔隙度的关系,通过实验检验,选出了公式ｌｎε１＋θ２ｌｎε２,能较好描述介电性质,对光谱选择性材料的设计具有参考价值。     

Autocorrelation Function of Hydrogen Atoms in Magnetic Fields

The autocorrelation function is an important quantity that can reflect the dynamical properties of the Rydberg wave packet and can be measured in experiments. Applying time-dependent perturbation theory and rotating wave approximation, we derive the autocorrelation function of the double-pulse laser describing the evolution of a Rydberg wave packet of hydrogen atoms in magnetic fields. The resulting expression is written as a sum of the modified Caussian terms. Each Caussian term comes from a parent semiclassical closed orbit. It provides a direct explanation and experimentally controllable measurement scheme, which allows us therefore to recognize the closed orbit and to determine its returning time in high precision.     

X-Ray Diagnostics of Microstructure Defects of Silicon Crystals Irradiated by Hydrogen Ions

Technical Physics - Features of formation and transformation of radiation defects in near-surface layers of silicon plates that are implanted with hydrogen ions are studied. Using the method of...     

氢等离子体气氛中退火多孔硅的表面和光荧光特性

用电化学腐蚀法制备了多孔硅(PS),在氢等离子体气氛中不同温度下对多孔硅样品进行了退火处理,并进行了光致发光(PL)谱和原子力显微镜(AFM)表面形貌的测量。不同退火温度给PS表面形态带来较大变化,也影响了其PL谱特性。在退火的样品中观察到的PL谱高效蓝光和紫光谱带,我们认为主要源于量子限制发光峰和非平衡载流子被带隙中浅杂质能级所俘获而引起的辐射复合所产生的。在420—450℃退火处理的多孔硅的PL谱上观察到了一个未见诸于报道的紫光新谱带(3．24eV,382nm),其发光机理有待于进一步研究。     

High-Frequency Electrical Conductivity and Dielectric Function of Strongly Coupled Plasmas

Using the frequency-moments analysis of the electrical conductivity with quantum mechanical assumptions and with the help of sum rules a generalization of the Drude-Lorentz theory of the electrical conductivity is given. For Coulomb-systems (e.g. plasmas), a connection is formulated in this framework between the known static electrical conductivity and the high-frequency conductivity. In this way, we are able to give an expression of the high-frequency dielectric function.