Synergisms at surfaces involving radiation and solvents: nanometer scale implications

We present studies of the consequences of simultaneous exposure of inorganic single crystals to radiation and water. The first case consists of a biomineral namely CaHPO 4 2H2O (brushite) which is a wide band gap, hydrated inorganic single crystal. We examine the laser induced ion and neutral emissions accompanying 248-nm excimer laser radiation. Both types of emission are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 μA/cm 2 and doses of 102-103 mC/cm2. We show the that the enhancements in emission are strongly correlated with e-beam induced morphology changes (including recrystallization) on this unusual surface. We then examine similar effects on dry crystals such as NaCl and NaNO3 which are exposed to 10-5 Pa partial pressures of H2O. Again dramatic enhancements in radiation induced emissions are exhibited along with the generation of unique morphological structures with nanometer scale dimensions.

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