Capacitances and Differential Negative Resistances of MIM Structures

A study has been made of the oxide thickness dependence of the capacitance and the current—voltage characteristics (at 10−5 Torr) of the structures AlAl2O3Au. The thicknesses varied from 25 (oxide formed at air) to 500 Å. The value of the apparent dielectric constant decreases for very thin oxide films. Differential negative resistances have been observed for all diodes. The voltage for the minimum current and the current and the current after the minimum increase linearly with the thickness of the oxide. The results are explained by the existence of a high resistance domain with a thickness of about 10 to 20 Å at one of the metal oxide interfaces, probably the interface AlAl2O3. The decrease of the current is perhaps caused by an increase of the thickness of the domain. Structures with thicknesses of oxide e > 400 Å show a broad current maximum which is sometimes splitted in two maxima.