TSEE from Ar + -ion and/or X-ray irradiated alumina and spinel was investigated. A TSEE peak at 150°C from X-ray irradiated alumina was suppressed when the alumina was further irradiated by Ar + -ions. A TSEE peak at 300°C was observed for Ar + -ion irradiated alumina and was suppressed by the combined effect of Ar + -ion and X-ray irradiatifons. Only weak TSEE peaks were observed between 250 and 350°C in Ar + -ion irradiated spinels. Generally, sprayed spinel specimens showed weaker TSEE peaks than the specimens of a single-crystal spinel. This is attributable to the fact that a plasma-sprayed spinel becomes amorphous more easily than its single crystals. X-ray irradiated spinel single-crystal showed well-defined TSEE when they were not irradiated with Ar + -ions.
Implantation of ${\mathrm{Au}}^{+}$ ions into a single crystalline $12\mathrm{CaO}∙7{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ (C12A7) was performed at high temperatures with fluences from $1\ifmmode\times\else\texttimes\fi{}{10}^{14}$ to $3\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. This material is composed of positively charged sub-nanometer-sized cages compensated by extra-framework negatively charged species. The depth profile of concentrations of Au species was analyzed using Rutherford backscattering spectrometry. The measured optical spectra and ab initio embedded cluster calculations show that the implanted Au species are stabilized in the form of negative ${\mathrm{Au}}^{\ensuremath{-}}$ ions below the fluences of $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ (Au volume concentration of $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{21}{\mathrm{cm}}^{\ensuremath{-}3}$). These ions are trapped in the cages and exhibit photoluminescence (PL) bands peaking at 3.05 and $2.34\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ at temperatures below $150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. At fluences exceeding $\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$, the implanted Au atoms form nano-sized clusters. This is manifested in quenching of the PL bands and creation of an optical absorption band at $2.43\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ due to the surface plasmon of free carriers in the cluster. The PL bands are attributed to the charge transfer transitions$({\mathrm{Au}}^{0}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\mathrm{Au}}^{\ensuremath{-}})$ due to recombination of photo-excited electrons $({e}^{\ensuremath{-}})$, transiently transferred by ultraviolet excitation into a nearby cages, with ${\mathrm{Au}}^{0}$ atoms.
The influence of deuterium retention on the electron-impact secondary electron emission (SEE) is studied in isotropic graphite (ETU-10). The ETU-10 surface sheath voltage and its deuterium retention under deuterium plasma exposure were measured simultaneously. Deuterium retention was estimated using in situ nuclear reaction analysis. While deuterium retention increased with decreasing graphite sample temperature, the sheath voltage on the sample surface decreased. The sheath potential variation is considered to be due to the SEE yield variation, which was estimated using the sheath voltage. The estimated SEE yield value increased by approximately 10% as the deuterium retention rose by a factor of two.
