Direct observation of local hot electron transport through Al2O3 tunnel junctions

A modified ballistic electron emission microscopy (BEEM) technique using local transport of hot electrons through a buried interface, was successfully applied to study the Al2O3 barrier in the Co/Al2O3/Ru tunnel junction. This technique enabled us to straightforwardly measure an effective barrier height of 1.7 eV and to observe the rise of the barrier height due to continuous current injection into a single point of the junction attributed to charging effects and/or degradation of the barrier structure. Scanning over an area of 510 nm×510 nm showed a spatial inhomogenity of the barrier resulting in different dependencies of the BEEM current on the energy of the injected electrons