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A movable mass spectroscopy gas sampling apparatus has been established and a straight-line fit of silane depletion fraction f is proposed. The spatial density distributions of SiHn (n=0-3) radicals in silane radio frequency glow discharge have been measured by a mass spectrometer. The experimental results demonstrate that the densities of the neutral radicals have the peak value near the middle position of electrodes, and the densities of SiH2 and SiH3 are higher than those of Si and SiH in silane plasma. This reveals that SiH2 and SiH3 may be the primary precursors in forming the a-Si:H film.  相似文献   
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Radicals produced by the plasma enhanced chemistry vapour deposition technique in SiCl4 plasma are identified by mass spectrometry using our newly proposed straight-line fit method. Since flow rate is one of the most important parameters in depositing thin films, we present the effects of SiCl4 flow rate variation on SiCln (n 〈 3) densities. The experimental results demonstrate that Si and SiCln (n = 1, 2) densities decrease with increasing SiCl4 flow rate. After reaching the minimum values at a flow rate of 17 and 13sccm, respectively, Si and SiCln (n = 1, 2) densities slightly increase with further increase of flow rate to 20.5sccm. These results could be interpreted to which the depletion fraction of SiCl4 decreases and the residence time of SiCl4 molecule becomes shorter, with the increasing SICl4 flow rate. In order to obtain high-quality poly-Si films with high growth rate, it is better to use smaller flow rate of SICl4 source gas for depositing films.  相似文献   
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氧含量对BiFeOδ多晶陶瓷介电特性的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
常方高  宋桂林  房坤  王照奎 《物理学报》2007,56(10):6068-6074
采用固相反应法制备了不同含氧量的BiFeOδ多晶陶瓷样品,利用HP4294A阻抗分析仪测量了样品的介电特性随频率和氧含量的变化,用正电子湮没寿命谱学的方法研究了样品中因氧含量的变化所引起的结构缺陷. 实验结果表明:引入氧空位和氧填隙离子缺陷都会使介电常数减小,而介电损耗则随氧含量的增加而增加,二者的变化范围均在10%—35%之间;对不同氧含量的BiFeOδ样品,介电常数和介电损耗随测量频率的增加而减小. 氧空位的引入使得局域电子密度变小,正电子平均寿命τm增加. 在氧含量δ=2.99时电子密度最大(ne=3.90×1023/cm3),继续增加氧含量对正电子寿命与局域电子密度的影响不大. BiFeOδ样品的介电常数和介电损耗随氧含量的变化可以在空间电荷限制电导的框架下来理解.  相似文献   
4.
For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln (n=0-2) radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln (n=0-2) radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn (n=1, 2) radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.  相似文献   
5.
设计了一个取样位置能在射频辉光放电等离子体电极间自由移动的取样装置,用质谱计测量了SiCl4等离子体的离子信号。提出了一种线性拟合的方法用于计算SiCl4等离子体的消耗率,利用测量的离子信号,计算出了SiCl4等离子体中SiCln(n=0~2)中性基团的空间分布。实验结果表明,可移动质谱取样装置的设计是合理的;用线性拟合方法得到的等离子体消耗率和中性基团的相对密度,比以前的方法得到的更精确。  相似文献   
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娄艳辉  宋桂林  常方高  王照奎 《中国物理 B》2010,19(7):77702-077702
The influence of oxygen content on the dielectric property of BiFeO3 ceramics is studied by experiment and firstprinciples calculation.The experimental result demonstrates that the dielectric constant of BiFeO3 is strongly dependent on introduced oxygen and oxygen vacancies.By comparison with BiFeO3,the introduced oxygen and oxygen vacancies can lead to a reduction in dielectric constant of BiFeO δ at a lower frequency.The first-principles calculation also shows a similar result when photon energy is in a range of 2.0-4.1 eV.A likely explanation is that this oxygen content dependence may be ascribed to the distortion of Fe-O octahedron structure due to oxygen vacancies or excess oxygen ions in the crystal structure of BiFeO3.  相似文献   
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