Ion Implantation and Annealing of Oxides
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ION IMPLANTATION AND ANNEALING OF OXIDESt C.W. WHITE*, L.A. BOATNER*, P.S. SKLAD*, C.J. MCHARGUE*, S.J. PENNYCOOK*, M.J. AZIZ**, G.C. FARLOW***, AND J. RANKIN**** * Oak Ridge National Laboratory, Oak Ridge, TN 37831 ** Harvard University, Cambridge, MA02138 *** Wright State University, Dayton, OH 45435 "****Massachusetts Institute of Technology, Cambridge, MA02139 ABSTRACT Ion implantation damage and annealing results are presented for a number of crystalline oxides. In A12 03 , the amorphous phase produced by ion bombardment of the pure material first crystallizes in the (crystalline) y phase. This is followed by the transformation of y-Al 2 0 3 to a-A120 3 at a well defined interface. The activation energy for the growth of a alumina from y is 3.6 eV/atom. In CaTi0 3 , the implantation-induced amorphous phase transforms to the crystalline phase by solid-phase epitaxy (SPE). ZnO is observed to remain crystalline even after high implantation doses at liquid nitrogen temperatures. The near surface of KTaO 3 is transformed to a polycrystalline state after implantation at room temperature or liquid nitrogen temperature. INTRODUCTION Numerous investigations of ion implantation damage and subsequent annealing have been carried out for both elemental Si and Ge and compound (e.g., GaAs) semiconductors, but there are relatively few reports of similar studies of insulating materials and crystalline oxides. Ion implantation is being increasingly investigated as a method of altering the nearsurface optical, electrical, or mechanical properties of insulating materials1- 4 ; and, for many applications, it will be necessary to anneal the implanted material. We are investigating the use of ion implantation to modify the near-surface properties of a number of crystalline oxides. We find that the response of these materials to ion implantation damage varies markedly from one material to another, and that the annealing behavior is also significantly different. In this paper, we compare and contrast the results obtained for the cases of crystalline A1203, CaTiO,3 ZnO, and KTaO 3 . Experimental Details In the case of A12 03 , a stoichiometric implant (2 parts Al, 3 parts oxygen with ion energies adjusted to give the same projected range) at liquid nitrogen temperature was used to produce the amorphous phase of pure A12 03 on a crystalline a alumina substrate. In this case, a stoichiometric implant was employed so that the crystallization behavior could be deter5 2 In the case of CaTiO 3 low doses (~101 /cm ) for the pure material. mined of 2 O8 Pb were used to turn the near surface amorphous. For ZnO and KTa0 3 , the implanted species was 208 Pb at doses up to 101 7 /cm 2 . Annealing of the implanted crystals was carried out for time periods ranging from a few minutes to many hours. Annealing environments were Ar (for A12 03 ) or air tResearch sponsored by the Division of Materials Sciences, U.S. Department of Energy under contract DE-ACO5-840R21400 with Martin Marietta Energy Systems, Inc. Mat. Res. Soc. Symp. Proc. Vol. 74. 1987 Mat
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