Effect of heat treatment on UV-laser-induced positive ion desorption in CaHPO4 center dot 2H(2)O

We have investigated KrF excimer-laser-induced positive ion desorption from single-crystal brushite (CaHPO4. 2H(2)O), a model biomineral containing wa ter, and we show the effect of heat treatment on ion desorption. Time-of-fl ight peaks of Ca+ desorption from the heated-cleaved surface are similar to those from as-cleaved ones, but the ion intensity is 2 to 4 orders of magn itude larger. In addition to Ca+, desorption of CaO+, PO+, and P+ from the heated surface is also strongly enhanced. The heated-cleaved surface shows rough, platelet-like fine structures due to recrystallization. Surface defe cts created during recrystallization strongly couple with the 5 eV photons and dramatically enhance ion desorption.