Determination of the defect nature of MoO3 films using dielectric-relaxation currents

Abstract

A new technique, based on stimulated dielectric‐relaxation currents (DRC), has been successfully used to analyse the defect properties of Al–MoO3–Al systems. The particular aspect of the DRC technique used here consists of cooling the system to low temperatures with a voltage applied to the electrodes and then raising the sample temperature at a uniform rate with the electrodes short‐circuited. Pronounced structure is observed in the current‐temperature characteristics, which may be related directly to the donor (or trap) density and the donor (or trap) distribution. The measurements obtained from the Al–MoO3–Al samples have confirmed the existence of Schottky barriers at the interfaces and revealed the existence of a donor band in the MoO3, which is centered about an energy 0.27 eV below the bottom of the conduction band. The half‐width of the donor band is about 0.07 eV, and its density is approximately 1.5×1018 cm−3. These results are in excellent agreement with those obtained from previous ac and dc measurements. It has also been confirmed that an electrode‐limited to bulk‐limited transition occurs at about 0.6 V. The DRC technique is compared to the thermally stimulated current (TSC) technique, and it is concluded that the DRC method is the superior of the two, at least as far as thin films are concerned. Finally, the effect of Schottky barriers on conduction processes in thin films in general is discussed and it is shown that if they are present but overlooked, the interpretation of the data is invalid.