共查询到17条相似文献,搜索用时 140 毫秒
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非晶态碳薄膜由于具有极低的二次电子发射系数(secondary electron yield, SEY),在真空微波器件与设备异常放电领域引起了广泛关注.然而,非晶态碳薄膜对二次电子发射影响的动态过程及微观机理仍缺乏了解.本文采用Monte Carlo方法,建立了Cu表面非晶态碳薄膜的二次电子发射数值模拟模型,能够精确地模拟电子与薄膜及基底材料的散射及二次电子发射的微观物理过程.结果表明,随着薄膜厚度从0 nm增加至1.5 nm时, SEY峰值下降了大约20%;继续增大厚度, SEY峰值不再下降.然而,当薄膜厚度大于0.9 nm时,SEY曲线呈现出双峰形态,但随着薄膜厚度增加至3 nm,第二峰逐渐减弱甚至消失.电子散射轨迹和二次电子能量分布结果,表明这种双峰现象是由于电子在两种材料中散射所致.相比以往模型,所提模型考虑了功函数的变化以及界面势垒对电子散射路径的影响.该模型从微观层面上解释了SEY曲线双峰现象形成的原因,相关的计算结果为非晶态碳薄膜对SEY的抑制规律提供了理论预测. 相似文献
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65nm以下线宽的纳电子器件,要求采用介电常数k小于2的超低介电常数材料作为层间和线间绝缘介质,等离子体增强的化学气相沉积技术制备的硅基纳米多孔薄膜,提供了实现k〈2的可能性,多孔SiCOH薄膜成为最具希望的候选材料,但是,纳米孔的引入带来了材料其他性能恶化、集成工艺困难、薄膜微结构分析等许多新问题.文章介绍了多孔SiCOH(超)低k薄膜研究的主要进展及面临的挑战. 相似文献
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采用磁控二靶(Ga30Sb70和Sb80Te20)交替溅射方法制备了新型Ga30Sb70/Sb80Te20纳米复合多层薄膜, 对多层薄膜周期中Ga30Sb70层厚度对相变特性的影响进行了研究. 结果表明, 多层薄膜的结晶温度可以通过周期中Ga30Sb70层厚度进行调节, 且随着Ga30Sb70层厚度的增加而升高. Ga30Sb70/Sb80Te20纳米复合多层薄膜的光学带隙随Ga30Sb70层厚度的增加而增大. 采用皮秒激光脉冲抽运光探测技术研究了多层薄膜的瞬态结晶动力学过程, 利用不同能量密度的皮秒激光脉冲可以实现Ga30Sb70/Sb80Te20多层薄膜非晶态和晶态的可逆转变. 相似文献
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在传统单一孔隙率多孔材料中引入宏观尺度的周期性梯度穿缝结构设计,构造出梯度穿缝型双孔隙率多孔材料,其包含多孔材料基体微孔尺度与穿缝尺度两个尺度。采用分层等效的理论建模方法,将复杂梯度渐变问题变为多层均匀等效层叠加问题。针对不同特征尺寸的多孔材料薄层,分别采用低、高两种渗透率对比度双孔隙率理论,给出了其等效密度和动态压缩系数,再应用传递矩阵方法得到了相邻薄层之间的声压和质点速度传递关系并求得其表面声阻抗,从而建立了梯度穿缝型双孔隙率多孔材料的吸声理论模型。发展了多尺度材料声学有限元数值模型,在所考虑的100~3000 Hz频段范围内数值模拟结果完全吻合理论模型结果。理论与模拟分析了多尺度结构参数对双孔隙率多孔材料吸声性能的影响,结果表明引入多尺度梯度结构设计能够显著提高单一孔隙率多孔材料的吸声性能,且穿缝尺度比穿缝梯度影响更为显著;精细数值模拟获得的声压和能量密度分布云图揭示了多尺度结构设计的吸声增强机制。该工作可用于指导双孔隙率多孔材料的多尺度结构设计,从而提高多孔材料的中低频吸声性能。 相似文献
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W.D. Liu K.X. Liu Q.Y. Chen J.T. Wang H.H. Yan X.J. Li 《Applied Surface Science》2009,255(23):9343-9347
Using an adjusted explosive welding technique, an aluminum plate has been coated by a Fe-based metallic glass foil in this work. Scanning electronic micrographs reveal a defect-free metallurgical bonding between the Fe-based metallic glass foil and the aluminum plate. Experimental evidence indicates that the Fe-based metallic glass foil almost retains its amorphous state and mechanical properties after the explosive welding process. Additionally, the detailed explosive welding process has been simulated by a self-developed hydro-code and the bonding mechanism has been investigated by numerical analysis. The successful welding between the Fe-based metallic glass foil and the aluminum plate provides a new way to obtain amorphous coating on general metal substrates. 相似文献
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A detailed numerical modeling is performed to investigate coupled heat transfer of natural convection, radiation and conduction in high-temperature multilayer thermal insulation (MTI), which consists of high-porous, non-gray semitransparent fibrous materials and reflective foils. Radiation within fibers, radiation between fibers and the reflective foils, conduction within fibers and convection from the fibers to the surrounding fluid are considered. Macroscopic (porous media) modeling is used to determine velocity, pressure and temperatures fields for fibrous insulation with a random packing geometry under natural convection, whereas the radiative transfer equation (RTE) is used to solve the radiative heat flux for non-gray materials. Key features of the macroscopic model include two-dimensional effects, non-gray radiative exchange, and the relaxation of the local thermodynamic non-equilibrium (LTNE). This model was validated by comparison with experimental data and it was used to investigate natural convection of coupled heat transfer in multilayer insulation, numerical results showed that natural convection is more likely to occur when the heated/cooled rate is low, while natural convection can be ignored in simulating steady-state coupled heat transfer in MTI. 相似文献
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Xinwen Huang 《Applied Surface Science》2009,255(7):4274-4278
The effect of the amorphous thin layer on the surface growth of amorphous/crystalline binary multilayer films has been studied by using a continuum model. It is shown that both the surface roughness and the growth exponent of amorphous/crystalline binary multilayer films decrease with increasing thickness ratio between amorphous and crystalline layers. Our simulations have also revealed, in contrast to the monotonous rise in surface roughness observed in single-layer films grown on flat substrates, the surface growth of a multilayer film consists of two processes: interface smoothing and roughening, namely the film roughness decreases during the growth of amorphous thin layers but increases monotonously during the growth of crystalline thin layers. The observed interface smoothing and roughening can be obviously influenced by the change in the thickness ratio between amorphous and crystalline layers. The rise in thickness ratio between amorphous and crystalline layers enhances the interface smoothing effect but lowers the interface roughening effect and consequently shows a marked smoothing effect on the surface roughness. 相似文献