Au-doped MgO films were prepared by reactive sputtering of individual Mg and Au targets, and the Au doping effect on the electron-induced secondary electron emission (SEE) performance was explored by means of surface analysis, first-principle calculation, and electrical characteristic measurement. The results show that the size enlargement of MgO grains and the reduction of surface work functions induced by Au doping are the main reasons for the increase of the SEE coefficient (δ). Additionally, the superior SEE degradation property of the Au-doped MgO film under continuous electron bombardment results from the improvement of electrical conductivity. Through the optimization of Au doping concentration (x), Au-doped MgO film with an x value of 3.0% was found to have the best SEE performance due to its highest SEE coefficient and longest duration of maintaining a relatively high SEE coefficient; its maximum δ value reached 11.5—an increase of 32.2% in comparison with the undoped one.
For special instruments or equipments including particle accelerators, space microwave devices and spacecrafts, the suppression for electron-induced secondary electron emission (SEE) occurring on the component surfaces is of great significance due to a negative influence caused by SEE on their normal operations. In this paper, amorphous carbon (a-C) films were prepared on stainless-steel substrates by radio frequency magnetron sputtering, and the effects of substrate temperature (Ts) and continuous electron bombardment on the microstructure and secondary electron emission yield (SEY) of a-C film were investigated in order to achieve a better inhibition for SEE. The experimental results show that a rise of Ts during the a-C film preparation is conducive to a SEY reduction and an increase of multipactor threshold due to the increases of surface roughness and sp2 bond content. In addition, although the SEY of a-C film has a slight increase with the rise of electron bombardment time, the a-C film sample with a lower SEY keeps its lower SEY all the time during continuous electron bombardment. The a-C film prepared at Ts of 500 °C has the lowest SEY peak value of 1.09 with a reduction of 30.6% in comparison with the stainless-steel substrate.
To improve the electron-induced secondary electron emission (SEE) properties of MgO/Au composite film, the strategy of Al doping in the MgO surface layer is adopted and investigated. For an MgO/Au film, Al doping in its MgO surface layer results in a slight increase of its grain size as well as a reduction of its surface roughness according to microstructure characterizations and also causes the decreases of both the band gap and work function of MgO crystal on the basis of the first-principles calculations, all of which have a close relationship with the improvement of secondary electron yield (SEY) demonstrated by the SEE measurement. An MgO/Au film including an Al-doped MgO surface layer with a doping ratio of 4.4% has an SEY of 4.7 with an increase of 14.6% at a primary electron energy (Ep) of 200 eV and the maximum SEY of 10.4 with an increase of 8.3% at Ep of 1100 eV in comparison with an MgO/Au film including an undoped MgO surface layer.
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