adjacent materials etc in one example the energetic species 206 include processes other than ion implantation to place metal ions 208 below the surface 205 of the electrode 204 for example the energetic species 206 includes gas cluster ion bombardment gcib or plasma implantation in one example the energetic species 206 include both metal ions and oxygen ions in later processing operations the implanted oxygen ions combine with the implanted metal ions to form an intermetallic oxide fig3 shows formation of a mixed valent oxide 210 over the electrode 204 examples of mixed valent oxides 210 include any of several magnetite perovskite oxide materials that exhibit resistive switching behavior for example praseodymium calcium manganese oxide prcamno or lanthanum calcium manganese oxide lacamno fig3 also shows a top electrode 212 formed over the mixed valent oxide 210 in operation as a memory cell a resistive state corresponding to stored data is stored in the mixed valent oxides 210 when a potential is placed between the electrode 204 and the top electrode 212 if the resistive state of the mixed valent oxides 210 is relatively low a current will conduct between the electrode 204 and the top electrode 212 indicating a stored state formation of mixed valent oxide.