Single-crystal magnetotunnel junctions

We have grown epitaxial single-crystal magnetotunnel junctions using Fe(001 ) substrates, MgO(001) spacers and Fe top electrodes. We have used scanning tunneling microscopy and atomic force microscopy to measure the tunneling characteristics as a function of position and demonstrated that local tunne ling can be obtained such that the buried MgO can be characterized with nm resolution. Local I(V) curves revealed that most of the area had intrinsic tunneling properties corresponding to the proper MgO tunneling barrier. A s mall fraction of the scanned areas showed localized spikes in the tunneling current which are most likely caused by defects in the MgO. (C) 2001 Ameri can Institute of Physics.