Formation of amorphous tracks in KTiOPO4 during swift heavy ion implantation

Structural damages in KTiOPO4 (KTP) single crystals caused by swift Kr- and Xe-ions at room temperature were studied by a combination of cross-section al transmission electron microscopy (XTEM) and Rutherford backscattering sp ectroscopy (RBS). z-cut flux grown KTP crystals were implanted with 150 MeV Kr-ions at ion fluences between 3 x 10(11) and 4 x 10(12) cm(-2) and with 250 MeV Xe-ions at an ion fluence of 3 x 10(12) cm(-2). An ion fluence depe ndent damage production is observed in the region of dominating electronic excitation. At low ion fluences, well-separated amorphous latent tracks wit h diameters of about 10 nm were observed within a superficial layer. Track diameters decrease with increasing depth z until z similar to 16 mu m, and in larger depths no tracks are detectable. By increasing the ion fluence, a successive track accumulation leads to the formation of a continuous amorp hous layer, The fluence dependence of the damage evolution as monitored by RES can be described in the framework of the overlap damage model introduce d by Gibbons [1] under the assumption that single tracks do not overlap. Th e track diameter derived from this model is in excellent agreement with tha t determined by XTEM. Complete amorphisation is accompanied by a swelling o f the implanted layer (about +4%). (C) 2000 Elsevier Science B.V. All right s reserved.