4.2K下稀有气体次级电子发射的测量
Measurements of the Secondary Electron Emission from Rare Gases at 4.2K
摘要：
测量了4.2K下氖、氩、氪和氙在靶上凝聚时的次级电子产额（SEY）与入射能量和覆盖率的关系。束流能量在100 eV ~ 3 keV之间，对氖、氩、氪和氙的最大覆盖率分别为12000、4700、2500和1400个单层。这些覆盖范围的SEY结果可以被认为是只属于被研究的气体，而不受靶材料的影响。对于所有气体，SEY对初级束能量的依赖性仅包括上升部分，因此，对于3 keV的束能量已经获得了最大测量SEY值，并且相应地对于氖、氩、氪和氙已经获得了62、73、60.5和52。第一次交叉的值对于氖为21 eV，对于氩为14 eV，对于氪为12.5 eV，对于氙为10.5 eV。由于束流冲击而产生的跨膜内场会对SEY测量产生很大的影响，这就要求束流减小到9.0E-10A。射束撞击的持续时间在500 μsec和250 μsec之间变化。有人发现，可靠的SEY测量也可以采取在带电表面上，如果电荷是由于电子束与更高能量的电子碰撞而获得的。所有SEY测量一次应用的覆盖范围已进行了整个范围的入射能量从3千电子伏下降到100 eV，而不更新的膜。沉积膜内部的孔的发展可以显著增加SEY，如在加热靶期间所观察到的。
英文摘要：
Dependence of the secondary electron yield (SEY) from the primary beam incident energy and the coverage has been measured for neon, argon, krypton and xenon condensed on a target at 4.2K. The beam energy ranged between 100 eV and 3 keV, the maximal applied coverage have made up 12000, 4700, 2500 and 1400 monolayers correspondingly for neon, argon, krypton and xenon. The SEY results for these coverages can be considered as belonging only to investigated gases without influence of the target material. The SEY dependencies versus the primary beam energy for all gases comprise only an ascending part and therefore, the maximal measured SEY values have been obtained for the beam energy of 3keV and have made up 62, 73, 60.5 and 52 for neon, argon, krypton and xenon correspondingly. Values of the first cross-over have made up 21 eV for neon, 14 eV for argon, 12.5 eV for krypton and 10.5 eV for xenon. An internal field appearing across a film due to the beam impact can considerably affect the SEY measurements that demanded the beam current to be reduced till 9.0E-10A. Duration of the beam impact varied between 500 μsec and 250 μsec. It was found that reliable SEY measurements can also be taken on a charged surface if the charge was acquired due to beam impact with electrons of higher energy. All SEY measurements for once applied coverage have been carried out for whole range of incident energies from 3 keV down to 100 eV without renewing the film. Developing of pores inside of a deposited film can significantly increase the SEY as it was observed during warming up the target.
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