Ballistic electron microscopy study of ultrathin oxidized aluminum barriers for magnetic tunnel junctions

Ballistic electron emission microscopy has been used to study thin aluminum oxide tunnel junction barriers formed both by magnetron sputter deposition and thermal evaporation. We have found that the barriers made by oxidation of evaporated Al become fully formed at a significantly thinner mean depos ited thickness (similar to6 Angstrom) than junctions made by sputter deposi tion. The effective barrier height of the aluminum oxide has been determine d to be 1.22 +/-0.05 eV and is independent of the method of deposition, thi ckness, and oxidation conditions. (C) 2001 American Institute of Physics.