Electron injection and interfacial reactions at valve metal oxides

The normally blocking contact between a valve metal oxide, e.g. Ta 2 O 5 , and a semiconducting oxide, e.g. MnO 2 , can be transformed into an electron injecting contact as a consequence of ionic polarization at the contact interface. Electron injection follows a Poole-Frenkel characteristic. The time-dependent development of the injection current at the anodization field of the valve metal oxide is directly related to the ionic charge transport in the interface and provides a very sensitive means of studying ionic charge transport and interface reactions through their effect on the electronic injection current. In this paper the results of experiments using Ta 2 O 5 and Nb 2 O 5 as typical valve metal oxides and FeO x , MnO x , NiO x and other representative contact oxides are reviewed.