The surface adsorption of gas molecules is a key factor limiting the secondary electron yield(SEY)of a material in many areas of applied physics.The influence of O_(2)adsorption on the SEY of metallic Ag is investigat...The surface adsorption of gas molecules is a key factor limiting the secondary electron yield(SEY)of a material in many areas of applied physics.The influence of O_(2)adsorption on the SEY of metallic Ag is investigated in this work.To account for the particle distribution,we propose a BET theory based on multilayer O_(2)physisorption model.Furthermore,based on the phenomenological model of secondary electron(SE)emission and by taking into account the different scattering processes between electrons and particles in the adsorbed layer,we develop a numerical model of SEY in the adsorbed state using Monte Carlo simulations.The relationships among O_(2)adsorption,adsorption layer thickness,and SEY variation characteristics are then examined through a series of experiments.After 12-h exposure to O_(2),the clean samples increases12%-19%of the maximum value of SEY and 2.3 nm in thickness of the adsorbed layer.Experimental results are also compared with the results from the MC model to determine whether the model is accurate.展开更多
Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield(SEY) of a metal with rough surfa...Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield(SEY) of a metal with rough surface topography. The results show that when the characteristic length scale of the surface, G, is larger than 1 × 10^(-7), the surface roughness increases with the increasing fractal dimension D. When the surface roughness becomes larger, it is difficult for entered electrons to escape surface. As a result, more electrons are collected and then SEY decreases. When G is less than 1 × 10^(-7),the effect of the surface topography can be ignored, and the SEY almost has no change as the dimension D increases. Then,the multipactor thresholds of a C-band rectangular impedance transfer and an ultrahigh-frequency-band coaxial impedance transfer are predicted by the relationship between the SEY and the fractal parameters. It is verified that for practical microwave devices, the larger the parameter G is, the higher the multipactor threshold is. Also, the larger the value of D,the higher the multipactor threshold.展开更多
钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(s...钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(secondaryelectronspectrum, SES)展开实验研究,其次利用相关唯象模型对测试数据进行分析;最后建立钼SEY的蒙特卡罗模型,用于分析功函数对SEY的影响规律。结果表明:钼SEY的最大值为1.77,相比镀银铝合金明显降低。当入射电子能量改变时,SES中真二次电子峰的最可几能量基本不变,而弹性背散射电子峰的位置和强度均随之改变。在各类二次电子中,真二次电子受功函数的影响最大。展开更多
CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on si...CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on silicon(Si)wafers,especially in the high-frequency range.In this paper,we have studied the major factors that influence the secondary-electron yield(SEY)in commercial Si wafers with different doping concentrations.We show that the SEY is suppressed as the doping concentration increases,corresponding to a relatively short effective escape depthλ.Meanwhile,the reduced narrow band gap is beneficial in suppressing the SEY,in which the absence of a shallow energy band below the conduction band will easily capture electrons,as revealed by first-principles calculations.Thus,the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.展开更多
基金Project supported by the Fund from the National Key Laboratory of Science and Technology on Space Mircrowave,China(Grant No.6142411112205)the National Natural Science Foundation of China(Grant No.62001376)。
文摘The surface adsorption of gas molecules is a key factor limiting the secondary electron yield(SEY)of a material in many areas of applied physics.The influence of O_(2)adsorption on the SEY of metallic Ag is investigated in this work.To account for the particle distribution,we propose a BET theory based on multilayer O_(2)physisorption model.Furthermore,based on the phenomenological model of secondary electron(SE)emission and by taking into account the different scattering processes between electrons and particles in the adsorbed layer,we develop a numerical model of SEY in the adsorbed state using Monte Carlo simulations.The relationships among O_(2)adsorption,adsorption layer thickness,and SEY variation characteristics are then examined through a series of experiments.After 12-h exposure to O_(2),the clean samples increases12%-19%of the maximum value of SEY and 2.3 nm in thickness of the adsorbed layer.Experimental results are also compared with the results from the MC model to determine whether the model is accurate.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1537211 and 61901361)。
文摘Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield(SEY) of a metal with rough surface topography. The results show that when the characteristic length scale of the surface, G, is larger than 1 × 10^(-7), the surface roughness increases with the increasing fractal dimension D. When the surface roughness becomes larger, it is difficult for entered electrons to escape surface. As a result, more electrons are collected and then SEY decreases. When G is less than 1 × 10^(-7),the effect of the surface topography can be ignored, and the SEY almost has no change as the dimension D increases. Then,the multipactor thresholds of a C-band rectangular impedance transfer and an ultrahigh-frequency-band coaxial impedance transfer are predicted by the relationship between the SEY and the fractal parameters. It is verified that for practical microwave devices, the larger the parameter G is, the higher the multipactor threshold is. Also, the larger the value of D,the higher the multipactor threshold.
文摘钼具有高熔点、低的热膨胀系数和极佳的稳定性,在等离子体推进和电真空器件领域具有广阔的应用前景,其二次电子发射特性也逐渐引起了研究者们的关注。本研究首先对钼的二次电子发射系数(secondary electron yield, SEY)和二次电子能谱(secondaryelectronspectrum, SES)展开实验研究,其次利用相关唯象模型对测试数据进行分析;最后建立钼SEY的蒙特卡罗模型,用于分析功函数对SEY的影响规律。结果表明:钼SEY的最大值为1.77,相比镀银铝合金明显降低。当入射电子能量改变时,SES中真二次电子峰的最可几能量基本不变,而弹性背散射电子峰的位置和强度均随之改变。在各类二次电子中,真二次电子受功函数的影响最大。
基金Project supported by the Administration of Science,Technology and Industry of National Defense of China (Grant No.HTKJ2021KL504001)the National Natural Science Foundation of China (Grant Nos.12004297 and 12174364)+3 种基金the China Postdoctoral Science Foundation (Grant No.2022M712507)the Fundamental Research Funds for the Central Universities (Grant No.xzy01202003)the National 111 Project of China (Grant No.B14040)the support from the Instrument Analysis Center of Xi’an Jiaotong University。
文摘CMOS-compatible RF/microwave devices,such as filters and amplifiers,have been widely used in wireless communication systems.However,secondary-electron emission phenomena often occur in RF/microwave devices based on silicon(Si)wafers,especially in the high-frequency range.In this paper,we have studied the major factors that influence the secondary-electron yield(SEY)in commercial Si wafers with different doping concentrations.We show that the SEY is suppressed as the doping concentration increases,corresponding to a relatively short effective escape depthλ.Meanwhile,the reduced narrow band gap is beneficial in suppressing the SEY,in which the absence of a shallow energy band below the conduction band will easily capture electrons,as revealed by first-principles calculations.Thus,the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.
