Magnesium ions were implanted into highly crystallineYBa2Cu3O7(YBCO) thin films for the purpose of patterning. Films were implanted at doses corresponding to Mg contents ofx=0.008,0.02, and 0.04 in the formulaYBa2(Cu1−xMgx)3O7.High temperature annealing (900 °C) of films implanted below the solubility limit was successful in obtaining single phase, Mg doped YBCO films with finite resistivities at 77 K and x-ray (005) rocking curve widths<0.15°.An electron probe microanalysis on a film patterned using Mg implantation revealed that lateral diffusion of Mg ions resulting from annealing was limited to only a few microns. The superior quality of a top layer film indicated that Mg ion implantation is suitable for multilayer patterning. ©1997 American Institute of Physics.