The calcium aluminate electride ${[{\mathrm{Ca}}_{24}{\mathrm{Al}}_{28}{\mathrm{O}}_{64}]}^{4+}{({\mathrm{e}}^{-})}_4$ (C12A7:${\mathrm{e}}^{-}$) is chemically and thermally stable in ambient atmosphere, offers strong electron donating capabilities and exhibits an intrinsic work function of 2.4 eV. Thus, it is an attractive material for electron emitter and low work function applications. For an implementation in negative hydrogen ion sources, where the electride could serve as a converter surface for the ${\mathrm{H}}^{-}$ production, compatibility with moderate vacuum conditions and exposure to low pressure low temperature hydrogen plasmas must be ensured. Hence, the stability and work function performance of a polycrystalline C12A7:${\mathrm{e}}^{-}$ sample are investigated under ion source relevant vacuum ($\sim {10}^{-6}$ mbar) and plasma conditions (electron temperature $\sim 2$ eV, electron density $\sim {10}^{16}{\mathrm{m}}^{-3}$). The work function is measured via the photoelectric effect, showing that long-term hydrogen plasma exposure results in a steady-state surface work function of $2.75\pm 0.10$ eV. Since the electride is very sensitive to surface contaminations, an increase of the surface work function occurs as soon as the plasma is switched off. Vacuum heat treatment of the degraded C12A7:${\mathrm{e}}^{-}$ surface after plasma activation leads to a work function minimum of 2.9 eV for temperatures in the range of 670–770 K. Exceeding a temperature of $\sim 770$ K leads to an increase of the C12A7:${\mathrm{e}}^{-}$ surface work function. The sample is stable during long-term hydrogen plasma exposure (up to 10 h total plasma-on time tested) and no plasma-induced erosion is observed.

中文翻译：

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暴露于低压低温氢等离子体的C12A7氮化物表面的功函数性能

铝酸钙驻极体 ${[{\mathrm{钙}}_{24}{\mathrm{铝}}_{28}{\mathrm{Ø}}_{64}]}^{4+}{（{\mathrm{Ë}}^{-}）}_4$ （C12A7：${\mathrm{Ë}}^{-}$）在环境大气中化学和热稳定，具有强大的给电子能力，并具有2.4 eV的固有功函数。因此，对于电子发射器和低功函数应用，它是一种有吸引力的材料。对于在负氢离子源中的实施方案，其中的驻极体可以充当${\mathrm{H}}^{-}$必须确保其生产，与中等真空条件的相容性以及暴露于低压低温氢等离子体中。因此，多晶C12A7的稳定性和功函数性能：${\mathrm{Ë}}^{-}$ 样品在离子源相关真空下进行研究（$〜{10}^{-6}$ mbar）和等离子体条件（电子温度） $〜2$ eV，电子密度 $〜{10}^{16}{\mathrm{米}}^{-3}$）。功函数是通过光电效应测量的，表明长期暴露于氢等离子体中会导致稳态表面功函数为$2.75\pm 0.10$ eV。由于电子化合物对表面污染非常敏感，因此一旦关闭等离子体，表面功函数就会增加。降解的C12A7的真空热处理：${\mathrm{Ë}}^{-}$ 在670-770 K范围内的温度下，等离子体活化后的表面导致的功函数最小值为2.9 eV。 $〜770$ K导致C12A7的增加：${\mathrm{Ë}}^{-}$表面功函数。该样品在长期暴露于氢等离子体中（经测试的总等离子体开启时间长达10小时）是稳定的，并且未观察到等离子体引起的腐蚀。