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1.
Low-dimensional structures formed by irradiation of laser   总被引:4,自引:0,他引:4  
Some kinds of low-dimensional nanostructures can be formed by irradiation of laser on the pure silicon sample and the SiGe alloy sample. This paper has studied the photoluminescence (PL) of the hole-net structure of silicon and the porous structure of SiGe where the PL intensity at 706nm and 725nm wavelength increases obviously. The effect of intensity-enhancing in the PL peaks cannot be explained within the quantum confinement alone. A mechanism for increasing PL emission in the above structures is proposed, in which the trap states of the interface between SiO2 and nanocrystal play an important role.  相似文献
2.
Self-assembled germanium nano-structures by laser-assisted oxidation   总被引:3,自引:0,他引:3  
黄伟其  刘世荣 《中国物理》2006,15(2):389-393
The investigation on the oxidation behaviour of Si1-xGex alloys (x=0.05, 0.15, and 0.25) is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence (PL) spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan (UHFR) method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.  相似文献
3.
A GENERATION OF EXACTLY SOLVABLE ANHARMONIC SYMMETRIC OSCILLATORS   总被引:3,自引:0,他引:3  
刘克家 《中国物理》2001,10(4):277-281
Using the ideas of supersymmetric quantum mechanics, we exactly solve a continuous family of anharmonic potentials, which are the supersymmetric partners of the linear harmonic oscillators. The family includes a series of potentials in which the excited-state energy is the same as that of the harmonic oscillators, but the ground-state energy can be any value lower than the excited states. The shape of the potential is variable, which includes the double-well and triple-well potentials. All the potentials obtained in this paper are free of singularities, and the supersymmetry of the solutions is unbroken.  相似文献
4.
NEW EXACTLY SOLVABLE SUPERSYMMETRIC PERIODIC POTENTIALS   总被引:3,自引:0,他引:3  
刘克家  何力  周国利  伍玉娇 《中国物理》2001,10(12):1110-1112
Using the formalism of supersymmetric quantum mechanics, we give an exact solution for a family of one-dimensional periodic potentials, which are the supersymmetric partners of the potential proportional to the trigonometric function cos(2x) such that the Schr?dinger equation for this potential is named the Mathieu equation mathematically. We show that the new potentials are distinctly different from their original ones. However, both have the same energy band structure. All the potentials obtained in this paper are free of singularities.  相似文献
5.
Quantum confinement analysis of nanostructures in oxidation of SiGe alloys   总被引:2,自引:0,他引:2  
黄伟其  刘世荣 《中国物理》2004,13(7):1163-1166
We report the investigation on the oxidation behaviour of Si_{1-x}Ge_x alloys (x=0.05, 0.15, and 0.25). It was found for the first time that a nanocap (thickness: 1.6-2.0nm) was formed on the oxide film after fast oxidation. Some new peaks in photoluminescence spectra were discovered, which could be related to the Ge nanocap, the Ge nanolayer (thickness: 0.8-1.2nm) and the Ge nanoparticles (with various diameters from 2.6nm to 7.4nm), respectively. A suitable model and several new calculating formulae combined with the Unrestricted Hartree-Fock-Roothaan (UHFR) method and quantum confinement analysis have been proposed to interpret the PL spectra and the nanostructure mechanism in the oxide and Ge segregation.  相似文献
6.
ICP-AES测定黔产天麻中微量元素   总被引:2,自引:0,他引:2  
李翠芹  陈桐 《光谱实验室》2007,24(4):570-573
用干法灰化,电感耦合等离子体-原子发射光谱法(ICP-AES)测定黔产野生和栽培天麻中人体必须微量元素的含量,实验证明,用干法灰化黔产野生和栽培天麻,样品消解完全,可以满足ICP-AES的检测要求,在选定的最佳条件下用ICP-AES检测各元素回收率在82%-99.5%之间,检出限为5-12ng·mL-1,该方法的相对标准偏差小于3.2%.为天麻中微量元素的测定提出了一个准确可行的方法,并为黔产野生及栽培天麻的开发提供可靠的依据.  相似文献
7.
非晶氧化锆水合物红外研究   总被引:2,自引:0,他引:2       下载免费PDF全文
用红外吸收光谱(IR)结合X射线衍射(XRD)、差热(DTA)和理分析(TG)详细研究了氧化锆前驱物(溶胶凝胶法制得的非晶态氧化锆水合物)的结构,实验结果表明在非晶态氧化锆水合物中有三种不同的近程结构,它表现为不同条件下制得的非晶氧化锆水合物的红外吸收谱在1700~1200cm^-1水和羟基的弯曲振动吸收区出现1633、1551、1400和1340cm^-1四个不同的羟基吸收峰,这表明样品中有三种  相似文献
8.
微波消解ICP-AES测定桔梗中微量元素   总被引:2,自引:1,他引:1  
采用微波消解样品,电感耦合等离子体-原子发射光谱法(ICP-AES)测定了中药材桔梗中Cu、Li、Mn、Co、Zn、Cr、Mg、Ga、Sr、Fe等微量元素的含量。在最佳仪器工作条件下,各元素的加标回收率在86.5%—111.0%,相对标准偏差RSD〈4.0%,实验结果可为桔梗中微量元素与其药效的相关性提供科学依据。  相似文献
9.
几种硝基苯类炸药在外电场作用下的分子特性   总被引:1,自引:0,他引:1       下载免费PDF全文
采用密度泛函理论中的B3LYP方法,在6-31G*水平上研究了外电场对一些硝基苯类炸药分子的总能量、偶极矩、分子轨道能级和前线轨道能量差等分子特性的影响;考察了在外电场作用下分子前线轨道能量差与炸药的电火花感度之间的关系.结果表明,在外电场作用下分子总能量降低,偶极矩增大、前线轨道能量差减小;分子前线轨道能量差与炸药的电火花感度之间几乎线性相关,且外电场对这种线性相关性无明显影响.  相似文献
10.
Review of relaxation oscillations in plasma processing discharges   总被引:1,自引:0,他引:1  
Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a metallic chamber whose periphery is grounded through a slot with dielectric spacers. The oscillations of time-varying optical emission from the main discharge chamber show, for example, a high-frequency (- 40 kHz) relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency (- 3 Hz) oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasma in the slot, but usually not in the peripheral chamber. The kilohertz oscillations are modelled using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 mixtures are used. Oscillations of charged particles, plasma potential, and light, at frequencies ranging from a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75 1200 W. The region of instability increases as the plasma becomes more electronegative, and the frequency of plasma oscillation increases as the power, pressure, and gas flow rate increase. A volume-averaged (global) model of the kilohertz instability has been developed; the results obtained from the model agree well with the experimental observations.  相似文献
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