Determination of barrier oxidation states in spin dependent tunneling structures

X-ray photoelectron spectroscopy (XPS) was used to characterize spin depend ent tunneling (SDT) structures using plasma oxidized Ta as the insulating b arrier. We are able to determine the relative proportion of the different o xidation states of the insulating barrier material. Information available f rom this technique includes barrier oxidation states, thickness, and comple teness of oxidation. Information on the electrodes is also obtained: specif ically, Ta is found to diffuse into NiFe, and oxidation of Ni is observed. XPS is shown to be a powerful tool in characterizing the materials sets tha t comprise SDT devices. (C) 1999 American Institute of Physics. [S0021-8979 (99)04910-5].