We have developed a process to fabricate planar high-TcJosephson junctions using nanolithography and a 200 keV ion implanter. Conduction occurs in the ab plane and is interface free. We can systematically tune devices to operate at temperatures between 1 K and theTcof the undamaged superconducting material by varying the length of the weak link and by changing the amount of ion damage. All of the devices showed clear dc and ac Josephson effects. Measurement ofR(T)andIc(T)of the weak links revealed trends which were consistent with a proximity effect. ©1998 American Institute of Physics.