THERMAL ANNEALING OF AR ION-BOMBARDED LITHIUM TANTALATE (LITAO3) SINGLE-CRYSTAL

The effect of the different annealing ambients on the regrowth of the Ar ion amorphized LiTaO3 single crystal was investigated. Samples were amorphized on c+ face by 218 keV Ar ions at room temperature with dos e of 6 x 10(15) ions/cm(2) and then annealed at 550 degrees C, which w as below the Curie temperature (605 degrees C). The annealing gases st udied were wet O-2, dry O-2, wet Ar, and dry Ar. Optical measurements showed that room temperature Ar ion bombardment created oxygen vacanci es in the amorphized layer, which could only be annealed out in an O-2 ambient. Thermal annealing at 550 degrees C for 30 min resulted in re growth of the amorphized layer, and it was observed that oxygen ambien t annealing provided better regrowth than Ar ambient. Infrared spectro scopy showed that the hydrogen signal was enhanced when samples were a nnealed in wet ambient, which indicated hydrogen had diffused into the LiTaO3. The Li-7(p,alpha)He-4 nuclear reaction was used to study the possibility of Li loss during the annealing process. Transmission Elec tron Microscopy (TEM) showed that the Ar ion amorphized layer regrew i nto multidomain phase after 550 degrees C annealing.