Interaction of wide band gap single crystals with 248 nm excimer laser irradiation. VI. The influence of thermal pretreatment on laser desorption of positive ions from a water-containing ionic crystal (CaHPO4 center dot 2H(2)O)

Morphological changes during dehydration of single crystals containing latt ice H2O (hydrates) can be dramatic, leading to surfaces that are rough, pol ycrystalline, and laden with defects. Previous studies have shown that ioni c crystal surfaces containing point defects readily desorb energetic positi ve ions under UV excimer laser irradiation. In this work, we examine the co nsequences of exposing thermally pretreated single crystal brushite (CaHPO4 . 2H(2)O) to 30 ns pulses of 248 nm laser irradiation and show that the sur face modifications strongly enhance the emission of Ca+ and other positive ions. (C) 2000 American Institute of Physics. [S0021-8979(00)03714-2].